Evolution of the Inline Six.

[Clams Canino]

I would LOVE to see a **detailed** write-up on the evolution and eventual demise of the Merc Inline 6.

In my "vision" of this history we would start with the Marathon Six and cover the running production changes and improvements on a year by year basis, culminating in the 88 115hp (perhaps a 90 also) which I believe is the last of the species?

I know it's a tall order, but it would be nice to see all the sniglets of info in one reference document.

I'll do a sample paragraph(s) in the area of my knowledge.
Corrections are VERY welcome as well as added technical data regarding interchangability info as things evolved.

If we can consider this thing "a work in progress" it just may become the definitive refernce doc on the inlines someday.
________________________________________________

"Turning the corner from the 50's to 1960 brought the end of the "Mark" designations as well as the loss of the original 60ci Mark 75 "Marathon Six" powerhead. 1960 however, heralded the introduction of the brand new 76ci powerhead. For 1960 the 66ci Mark78A was retained as the Merc 700 and the new 76ci powerhead was designated the Merc 800.

In 1960 both of these engines were only available in direct reverse configurations. In 1961 the same two blocks were back with the welcome addition of of full gear shift lower units. 1961 is the only year that both Direct Reverse and Full Gear Shift were simultainiously available.

Overwhelming public responce to the FGS models signaled the end of the line for the Direct Reverse "Dockbuster" lower units. And in 1961 only two motors were only offered in FGS configuration. (This in and of itself is quite ironic as E.C.K. was adamant about not wanting to put FGS lower units on the Inline Sixs for fear of reliability issues with the extra power.)

A cosmetic note is that 1960 and 1961 uniquely featured chrome MERCURY lettering on the top cowling in place of the previous red or blue decals. Different letters were used for the left and right sides and they are not interchangeable. (there is also a rumor that the 700 and 800 has different *size* letters - please confirm someone?)

1962 was another year of big advancement. Introduced in 1962 was the new "power dome" combustion chamber, (could someone explain the exact differences) as well as the introduction of a new 90ci powerhead. The venrable 66ci powerhead got to live one final year as the 1962 Merc 700, (unchanged from the 1961). The 76ci powerhead with the new combustion chamber (and sporting an extra 5 horsepower) was upgraded from the 61 Merc 800 to the 62 Merc 850.

The real news however in 1962 was the all new 90ci powerhead in the new Merc 1000 "Phantom" becoming the first production outboard to break the 100hp barrier.

This engine was the first of the Inline Six's to be painted black, with the rest of the line to follow in a few years. To this day Mercury Black is properly designated "Phantom Black". The chrome MERCURY letters on the top cowl vanished in favor of a large decal on the wraparound. A new diode rectifier replaced the previous selinium plate models and there were significant changes to the starting solenoid and ignition coil resister / ballast system. (though the distributor and fireing order stayed the same as the 76ci Merc 800/850.)

1963 saw the Merc 1000 continue relatively unchanged. The 76ci powerhead was dropped. As a result the 1963 Merc 850 used a detuned version of the 90ci powerhead.

________________________________________

[Flat Out]

I know there are others one the board that have a wealth of knowledge when it comes to these motors. The inline six was the dominant hi-perf motor of it's day. As a kid we had a '62 Merc 850 and a '75 1500. My uncle had a '63 1000 which my cousin still has and another uncle had a '72 1400 blue stripe ?. My brother had a mint '81 or '82 115 wich came with his cottage but he got rid of it and the boat it was on.
Unfortunately time has not been kind to these to these old motors. Low octane gas has claimed many old motors. These motors have been out of production almost 15 years and good parts are getting harder to find. The race motors have become quite collectable. The 1500XS seens to be a crowd favorite. As with any hi-perf motor they were driven hard and hung up wet. Once the V6 came out many old six stackers were cast aside, now many of us are trying to restore/ rebuild these old motors.
I hope others will add to your history of the "Great white/black stack from Fond du Lac" actually the old ones were made in Cedarsburg, WI.
Keep it coming.

[Mark75H]

Very well done Ratbo.

Lets go to the very beginning of the cylinder Merc project. Behind Kiekhaefer's back, chief engineer C. D. Strang started development of the inline 6 as secret project. Three 2 cylinder crankshafts were welded together and two 4 cylinder blocks had one cylinder sawed off and were welded together. A six cylinder car distributer was grafted on in place of the magneto and a new motor was born. During development it was always covered or hidden whenever Carl was around. After it had been tested and adjusted, they called Kiekhaefer down to the dock and pulled a blanket off of the prototype. At first Kiekhaefer laughed out loud!! When he was done laughing they convinced him to take it for a test run.....when he returned to the dock he is reputed to have said "It speaks with authority. Build it."

The production motor was ready for the 1957 model year.

This first version, the "Mark75", got 60 hp from its 60 cubic inches. This motor is based very heavily on the 2 and 4 cylinder motors from which it was derived.....10 ci per cylinder and one 3/4" Tillotson AJ series carb per pair of cylinders feeding the Kiekhaefer internal reed valves. Even though there are 3 fuel pump pads, only 2 are used. The two pumps are piped in series to give greater suction/lift capability to the pump system to lift fuel from remote tanks low in the boat. Ignition came from a special 6 cylinder distirbutor that over comes what would be the normal limitiaitons of a 2 stroke 6 cylinder distributer by actually being two 3 cylinder ignitions incorporated in unision. 2 coils, 2 ballast resistors, 2 sets of points, one distributor. Inside the distributor, on the rotor button, there are 2 contacts that meet the spark plug contacts. One feeds from the bottom center coil brush in the normal way, the other from an insulated slip ring on the side. Each feeds only 3 cylinders because of the way the points trigger the coils. Back in the 50s lower unit technology wasn't yet developed to handle the power of such an outboard, so Kiekhaefer simply followed the example of some other steam drive and marine drive propulsion systems and set up the now famous "Direct Reverse" system. With this system the lower unit gears stay engaged all the time. Reverse is achieved by starting and running the motor counter clockwise instead of the normal clockwise. At the helm a special control box controls the throttle and selects which direction the motor will start and run. The throttle handle moves through a Z shaped gate and actuates an array of micro switches to stop the motor and allow starting in the desired rotation. On the top of the handle is a button that you press with your thumb to actuate the starter motor itself. The "pistol grip" shaped handle and thumb button strongly resemble a World War II fighter plane control stick and machine gun actuator....great symbols of power in 1957. There are 4 special parts on the motor for the Direct Reverse system. First and most obvious is the special starter. This big clunky thing has 2 drive gears. At rest one is in the normal position below the starter ring gear on the flywheel, the other is on the extended end of the starter shaft above the starter ring gear. The starter also has 2 solenoids. For forward one solenoid engages the starter motor to run counter clockwise...the lower drive gear runs up its spiral ramp and engages the flywheel gear turning the crankshaft clockwise. For reverse the other solenoid engages the starter motor to run clockwise and the upper drive gear runs down its spiral ramp to engage the flywheeel gear and turn the crankshaft counter clockwise. The motor's second special part is throttle linkage that pushes the carbs OPEN at both extremes of the throttle cable's throw. This is necessary to increase motor speed as one pulls the pistol grip throttle farther back to go faster in reverse as well as the normal throttle opening for forward. Special part number 3 is the Direct Reverse water pump. Regardless of which way the motor runs water must be pumped up to the powerhead. This is achieved with a water pump with two check valves. Each check valve is located a few degrees off of the water pump's "tight" side where the water is squeezed out of the pocket. The simple rubber check valve allows water to exit the chamber from whichever side it is being squeezed and not back down (into the pump) on the side where the impellor is opening the pocket to draw water in. OK so now you are wondering what special part #4 is.....










In the distributor there must be some mechanism to throw the ignition to the other side of TDC to compensate for "BEFORE" and "AFTER" TDC changing places. This is achieved with slack in the distributor drive shaft. The upper part of the distributor shaft that is driven by the distributor drive pulley is not the same piece as the shaft with the cams for the points and the rotor button. The coupling between these 2 shafts has quite a bit of slack. This allows the timing slip over to the other side of top.

To tell these powerheads from other similar Mercs the name "Marathon Six" is cast in on the fuel pump side.

[Clams Canino]

Nice going Sam!

I'll try to fill in the little gap between our two docs and get a seamless blend. I might need you to flesh that section out a bit.

In keeping with your anecdotal additions - I plan to re-edit my first piece to include the stories of how the FGS was snuck in and the story behind the black paint - as both of those fall in my 60 - 63 section.

-W

[Mark75H]

Hang on, Wayne or I'll have you re-editing the 60-63 thing again and again. Look at the crankshaft splines line of my "bolt patterns" post on John's board.

A minor correction on your original post: the last year of the 60ci Mark75 is 1958. The 60 hp 1959 Mark75A is a "detuned" 66ci Mark78/78A.

Replacement 60 ci blocks were still available after production of the original 6 cover (refers to the transfer/intake covers) motor went obsolete. These replacement blocks were "sleeved down" 66ci "siamese" intake cover castings. They still say "Marathon Six" but the font is smaller and the words "Full Jeweled" that do not appear on the 6 cover blocks appear with "Marathon Six" the same as found on the 66ci blocks which carry the "Super Marathon Six" name.

There is a bunch of 1961 stuff not yet mentioned on any of the boards.

[Raceman]

Sam, I wish you'd post the bolt patterns here also. I'm unfamiliar with "John's board".

[Mark75H]

No big deal. Until the 140 all actual bolt (stud) patterns are the same. There are a number of different gasket patterns with various exhaust and water inlet locations, so the parts books show different gaskets which has caused a lot of parts book jockeys to claim different bolt patterns, but the bolts are all in the same locations and the powerheads will at least start on the studs.

(I used the top 8 inches of a 1970ish driveshaft housing to make a super short housing for my 60 ci 1957 Mk75 powerhead, it bolted right on.)

Crankshaft splines: except for the 62 70 hp full gearshift all 60 and 66 ci motors use the smaller spline used on the 40 and 44 ci motors. All 76ci and larger use the same larger splines. What this means: if you want to jam an old 60 or 66 ci motor on a later driveshaft you need a 62FGS 70hp or 76ci 80/85 hp crank for bolt up only type work. Reverse would also work; if you found a Mk75 or Mk78 Merc 600/700 DR LU and have only a 76ci DR or 76 or 66 FGS motor you need the smaller spline crank from the old motor for work that doesn't require welding

There are some possible mis-matches with newer bigger main bearing bosses hitting webs that don't match in older driveshaft housings. Also possible shift/throttle linkage conflicts for direct bolt ups, but nothing that a big hammer can't fix, LOL.

[Mark75H]

Lets call the 100 hp motors 89ci to give us some extra definition when we get to the 92ci motor.

The firing order changes on the 76ci motor to rearrange which cylinders are adjacent in the two sets of tuned triples. The "Powerdome" combustion chamber puts the combustion chamber center more over the top flat land of the piston and I think it fills in some of the dead space shielded from the flame front by the deflector dam of the piston. Racers had been filling in this space with welded in "pads". Compression is increased, turbulence increases, dead "end gas" area decreases, decreasing the octane demand over a similar combustion chamber. Externally Powerdome spark plugs sit off center of the crankshaft and bores, earlier non Powerdome heads have the spark plugs on center with the bores and crank.

I think the 700 gets an exhaust divider, eliminating the common exhaust chamber for all 6 cylinders.

Sorry I still haven't addressed the changes for the 66ci Mk78/78A. Maybe Friday night.

[Clams Canino]

Lets go to the very beginning of the cylinder Merc project. Behind Kiekhaefer's back, chief engineer C. D. Strang started development of the inline 6 as secret project. Three 2 cylinder crankshafts were welded together and two 4 cylinder blocks had one cylinder sawed off and were welded together. A six cylinder car distributer was grafted on in place of the magneto and a new motor was born. During development it was always covered or hidden whenever Carl was around. After it had been tested and adjusted, they called Kiekhaefer down to the dock and pulled a blanket off of the prototype. At first Kiekhaefer laughed out loud!! When he was done laughing they convinced him to take it for a test run.....when he returned to the dock he is reputed to have said "It speaks with authority. Build it."

The production motor was ready for the 1957 model year.

This first version, the "Mark75", got 60 hp from its 60 cubic inches. To tell these powerheads from other similar Mercs the name "Marathon Six" is cast in on the fuel pump side. This motor is based very heavily on the 2 and 4 cylinder motors from which it was derived.....10 ci per cylinder and one 3/4" Tillotson AJ series carb per pair of cylinders feeding the Kiekhaefer internal reed valves. Even though there are 3 fuel pump pads, only 2 are used. The two pumps are piped in series to give greater suction/lift capability to the pump system to lift fuel from remote tanks low in the boat. Ignition came from a special 6 cylinder distirbutor that over comes what would be the normal limitiaitons of a 2 stroke 6 cylinder distributer by actually being two 3 cylinder ignitions incorporated in unision. 2 coils, 2 ballast resistors, 2 sets of points, one distributor. Inside the distributor, on the rotor button, there are 2 contacts that meet the spark plug contacts. One feeds from the bottom center coil brush in the normal way, the other from an insulated slip ring on the side. Each feeds only 3 cylinders because of the way the points trigger the coils. Back in the 50s lower unit technology wasn't yet developed to handle the power of such an outboard, so Kiekhaefer simply followed the example of some other steam drive and marine drive propulsion systems and set up the now famous "Direct Reverse" system. With this system the lower unit gears stay engaged all the time. Reverse is achieved by starting and running the motor counter clockwise instead of the normal clockwise. At the helm a special control box controls the throttle and selects which direction the motor will start and run. The throttle handle moves through a Z shaped gate and actuates an array of micro switches to stop the motor and allow starting in the desired rotation. On the top of the handle is a button that you press with your thumb to actuate the starter motor itself. The "pistol grip" shaped handle and thumb button strongly resemble a World War II fighter plane control stick and machine gun actuator....great symbols of power in 1957. There are 4 special parts on the motor for the Direct Reverse system. First and most obvious is the special starter. This big clunky thing has 2 drive gears. At rest one is in the normal position below the starter ring gear on the flywheel, the other is on the extended end of the starter shaft above the starter ring gear. The starter also has 2 solenoids. For forward one solenoid engages the starter motor to run counter clockwise...the lower drive gear runs up its spiral ramp and engages the flywheel gear turning the crankshaft clockwise. For reverse the other solenoid engages the starter motor to run clockwise and the upper drive gear runs down its spiral ramp to engage the flywheeel gear and turn the crankshaft counter clockwise. The motor's second special part is throttle linkage that pushes the carbs OPEN at both extremes of the throttle cable's throw. This is necessary to increase motor speed as one pulls the pistol grip throttle farther back to go faster in reverse as well as the normal throttle opening for forward. Special part number 3 is the Direct Reverse water pump. Regardless of which way the motor runs water must be pumped up to the powerhead. This is achieved with a water pump with two check valves. Each check valve is located a few degrees off of the water pump's "tight" side where the water is squeezed out of the pocket. The simple rubber check valve allows water to exit the chamber from whichever side it is being squeezed and not back down (into the pump) on the side where the impellor is opening the pocket to draw water in. OK so now you are wondering what special part #4 is.....
In the distributor there must be some mechanism to throw the ignition to the other side of TDC to compensate for "BEFORE" and "AFTER" TDC changing places. This is achieved with slack in the distributor drive shaft. The upper part of the distributor shaft that is driven by the distributor drive pulley is not the same piece as the shaft with the cams for the points and the rotor button. The coupling between these 2 shafts has quite a bit of slack. This allows the timing slip over to the other side of top.

GAP TO BE FILLED HERE
"Turning the corner from the 50's to 1960 brought the end of the "Mark" designations as well as the loss of the 60hp Mark 75 Marathon Six. 1960 however, heralded the introduction of the brand new 76ci powerhead. For 1960 the 66ci Mark78A was retained as the Merc 700 and the new 76ci powerhead was designated the Merc 800.

In 1960 both of these engines were only available in direct reverse configurations. In 1961 the same two blocks were back with the welcome addition of of full gear shift lower units. 1961 is the only year that both Direct Reverse and Full Gear Shift were simultainiously available. This came about as Kiekhaefer was adamant about not wanting to put FGS lower units on the Inline Six’s for fear of reliability issues with the extra power. Enter again Charlie Strang with yet another project behind Carl’s back. Only when he had the unit perfected did he let Big Carl in on the project and Carl only relented to offer FGS on the Inline Six’s so long as the Direct Reverse was also offered. Overwhelming public responce to the FGS models signaled the end of the line for the Direct Reverse "Dockbuster" lower units. From 1962 forward Inline Six motors were only offered in FGS configuration.

A cosmetic note is that 1960 and 1961 uniquely featured chrome MERCURY lettering on the top cowling in place of the previous red or blue decals. Different letters were used for the left and right sides and they are not interchangeable. (there is also a rumor that the 700 and 800 has different *size* letters - please confirm someone?)

1962 was another year of big advancement. Introduced in 1962 was the new "power dome" combustion chamber, as well as the introduction of a new 89ci powerhead. The "Powerdome" combustion chamber puts the combustion chamber center more over the top flat land of the piston and I think it fills in some of the dead space shielded from the flame front by the deflector dam of the piston. Racers had been filling in this space with welded in "pads". Compression is increased, turbulence increases, dead "end gas" area decreases, decreasing the octane demand over a similar combustion chamber. Externally Powerdome spark plugs sit off center of the crankshaft and bores, earlier non Powerdome heads have the spark plugs on center with the bores and crank. The venerable 66ci powerhead got to live one final year as the 1962 Merc 700, (unchanged from the 1961). The 76ci powerhead with the Powerdome combustion chamber (and sporting an extra 5 horsepower) was upgraded from the 61 Merc 800 to the 62 Merc 850.

The real news however in 1962 was the all new 89ci powerhead in the new Merc 1000 "Phantom" becoming the first production outboard to break the 100hp barrier.

This engine was the first of the Inline Six's to be painted black, with the rest of the line to follow. To this day Mercury Black is properly designated "Phantom Black". This time it was Charlie Strang’s mother who came up with the idea in response to the problem that the motors had grown so much that they were beginning to look unwieldy. “Well, a large woman always wears a black dress. Why don’t you paint it black?” Again Charlie set up a surprise viewing for E.C.K. When Carl saw the A-B comparison he said “MY GOD! Let’s paint them ALL black!” Also, the chrome MERCURY letters on the top cowl vanished in favor of a large decal on the wraparound. A new diode rectifier replaced the previous selinium plate models and there were significant changes to the starting solenoid and ignition coil resister / ballast system. (though the distributor and fireing order stayed the same as the 76ci Merc 800/850.)

1963 saw the Merc 1000 continue relatively unchanged. The 76ci powerhead was dropped. As a result the 1963 Merc 850 used a detuned version of the 90ci powerhead.

[Clams Canino]

I'm saving the bolt pattern stuff on ice for when we get to the year it changes. I'll work the crankshaft and firing order in next time I get a few minutes.


-W

[Clams Canino]

[QUOTE]Originally posted by Mark75H
[B]Lets call the 100 hp motors 89ci to give us some extra definition when we get to the 92ci motor.

Sam, are you refering to the 93.5ci powerhead?? I was gonna use the designations from the service manual IE 90 and 93.5 (as opposed to 89 and 92) so that a reader can easily cross reference our writing to the official Merc documentation. I changed it to 89 for now though, waiting on your reasoning??

-W

[LakeRacer99]

Wayne and Sam,
Great topic! I cant contribute much here but I'd love to learn. These towers really interest me.

Raceman,
A link to John Kwast's site...

http://www.pfs-ware.com/kwast/

Jason

[H2Onut]

Very good reading. Are yu guys going to the RUmble, got to meet some of these history guys....YOU ROCK

[Raceman]

Great reading guys. Sam, how about gearcase bolt patterns in the gearshift 6's. Someone said the other day that they thought some of the pre 70 engines had a different pattern on the lower. I've always thought that anything black would interchange. I'm sure the 1250 in question at the time will take the later stuff, but unsure where the change came and if there were only 2. The white stuff is noticeably different.

Incidentally, I've always thought the 61's were the only engines with the bolt on letters on the top cowl. I have a gearshift, shortshaft 61 800 with the letters, and a DR 700 without. There's also a DR 800 with and a GS 800, also with, but I don't know much about the history of these two or the year models. My 61 catalogue seems to show the GS 700 with the chrome letters and the DR 700 with the stickers, but I don't recall ever having seen a 700 with letters period. I'm supposed to have a 60 Catalogue also, but can't find it. If you've got one Sam, I sure would like a scan of the 800 & 700 pages.

One other engine that seems to be overlooked here is the Merc 600, available in 60 only. Would this not have been the replacement for the 60 HP Mark 75A?

Here's another trivial question: which 6 cyl white engine had no recoil starter on the top cowl?

[LakeRacer99]

This one? Merc 800?

[Clams Canino]

Off the top of my head I would say the 61 Merc 800 Direct Reverse didn't include a pull starter. poerhaps the 60 didn't as well. I'd say off hand that picture - if real - is one of 'em.

-W

[Mark75H]

That motor belongs to my buddy Dick Davis of Minneapolis and its a little "fixed up". Not sure what motor that top came off of. The lower unit is a Speedmaster, not the standard DR "Fleetmaster". Our buddy XSRaveau has one of the inbetween 1961 "Sportmaster" lower units with the 1.5:1 gear ratio. It is a little unremarkable in looks, to be honest.

Regarding the bottom of the driveshaft tower pattern: the gear shift units are longer in front of the drive shaft to accomodate the shift linkage. There might be a second increase in this length around 1963, but I'm pretty sure they are all the same after that. DaveS and I were looking at some of those in his shop one cold day last winter as we reviewed the different Speedmaster bolt patterns.

I have a '61 DR 700 that has pull start rope. I don't recall seeing a white top without a pull rope.

You are correct about the Merc 600. Like the Mark75A before it, it differs from the 700 only in having smaller carbs.

Here is a tidbit that belongs in 1959: The change from the round top cover to the "square" top cover with the larger rope shive (pulley) to giving more leverage to allow easier pull starting. With this change we said good bye to the original heavy cast aluminum front cover and introduce the lighter stamped aluminum front cover used until the end. Another 1959 option: chrome strips or chrome as a color.....WOW! The 1959 changes were a mid year thing and seem to be divided about half and half among the survivors.

Next time I'll jump back to the introduction of the 66ci Mark78.

As far as Merc literature being consistant calling the 89.9ci motors 90ci....not! Just like the 99.9/100 ci motors Merc literature is inconsistant and sometimes completely wrong. The big "Master Spec" pages from the 60's have a dozen or so errors. Somebody probably got fired over that, but if the stories we've heard about Carl's temper tantrums are true....they were rehired the next day with a raise.

[Raceman]

Ratbo's correct, it was the DR800. I found it interesting that the 800 wouldn't have it, while the 1000 in 62 still did. I've got several of those 61 cowls without the pull mechanism or hole.

[Raceman]

"Chrome strips or chrome as a color"

That kinda jogs a memory. Seems like I ran across an old engine with the lower pan chromed and was told it was original and an option. I can't remember anything else about it. I would've thought the pan had the round edges (58 and older style) but it's been a long time and I can't even remember who had the engine now. How about a little better description of "chrome as a color".

[Clams Canino]

[QUOTE]Originally posted by Mark75H
""I have a '61 DR 700 that has pull start rope. I don't recall seeing a white top without a pull rope.""

I have seen a 1961 800 DR without a pull rope. I used one of those covers to scavenge the letters off for my 800 FGS.

The question remains on the floor as to if the 1960 had the letters. If it did not - what did it use???

""As far as Merc literature being consistant calling the 89.9ci motors 90ci....not! Just like the 99.9/100 ci motors Merc literature is inconsistant and sometimes completely wrong. The big "Master Spec" pages from the 60's have a dozen or so errors.""

Sam, I'm basing my (not adament, but respectfull) advocacy for calling them 90 and 93.5 solely on the C-90-25500 Repair Manual and the Master Specification sheets in the back of it that were revised in 1969. My reasoning is that, anyone who "wasn't there" the first time around, like you, and has to learn this "anew" (like I just did) mostly has **that book** as thier basic "Bible" of knowledge as that's the one sold today. While that page still carries some errors (and you'll need to point out the less obvious ones) it is consistant regarding those 2 displacements and uses 90 and 93.5 "pretty much" across the board. As a case in point - I never ever knew them as anything different until you pointed it out - I don't thing anyone else new to the hobby would have many more clues than I would. Using numbers different from that reference material would have only confused me as to what somone was talking about. This is a case where I have no pre-concieved notions as I just wasn't there when they had 6 names. :)

-W

[Clams Canino]

I cut and pasted all this into the master document to be fleshed in when 1958 is done. Good stuff!!

-W


[QUOTE]Originally posted by Mark75H
[Here is a tidbit that belongs in 1959: The change from the round top cover to the "square" top cover with the larger rope shive (pulley) to giving more leverage to allow easier pull starting. With this change we said good bye to the original heavy cast aluminum front cover and introduce the lighter stamped aluminum front cover used until the end. Another 1959 option: chrome strips or chrome as a color.....WOW! The 1959 changes were a mid year thing and seem to be divided about half and half among the survivors.

Next time I'll jump back to the introduction of the 66ci Mark78.

[Clams Canino]

Wrote the last chapter tonight incorporating what I learned from my 1984 and 1987.
_________________________

Chapter Five: The Writing On The Wall.

(not done)

Chapter Six: Out with a Roar instead of a wimper. (propshaft ratings)
When all is said and written about the inlines, we can’t ignore these, the last of the species. These last four years saw the old girl get the “new” integral power trim assemblies in 1985 and, thanks to propshaft ratings finally coming into vogue at Mercury, the magic returned for a final bow. These last (propshaft rated) motors featured the big open reed stops and the power ported pistons of the glory days gone by. And, they had the big ol’ ports in the cylinders back too! (with slightly different timing)
These last of the titans may in fact be the ultimate ski-boat motor of all time with gobs of torque to rip a skier or two (or three) out of the water, yet can easily pull up past 6000 rpm without a complaint in the world. With the rock solid ADI ignition and modern power-trim units, these motors represent the end of the evolution for the Tower of Power yet live up to both the name and reputation of these very special motors.

[gaineso]

Hey guys.

I've got an '86 115 (Mariner Grey) and love it. Bought new, actually demo, in '87 and had it since.

Fairly heavy Glasstream 15V, 22" TurboII, Super High Jacker 6" back and 4" below pad. Planes in less than 2 boat lengths and still runs over 60 at 6200 R's.

Always use 40:1 Premium Plus oil and mid-grade gas.

Question?

Should I switch to premium (92or 93) gas?

Thanks for the history. Having a "Tower of Power" myself, I find it incredibly interesting and look forward to more installments.

[Clams Canino]

In my humble opinion you are fine as you are. Why argue with 15 years of success. :)

I use mid-grade and 40/1 on mine too. It's the early 70's ones with the high dome pistons that are the "most finiky".

-W

[gaineso]

Good point!

[Still crazy]

If you guys have not read it yet, you have to get yourself a copy of the "Old Outboard Book" by Peter Hunn.

I have an old Johnson in my mom's garage and took a copy of the book out of the library to find the year of the motor, which turned out to be a 1947. After that, I couldn't put the book down. The chapter on Kiekhafer was real interesting and had some real hilarious stories about some of the early Merc's.

I'm going to buy myself a copy to keep.

[Raceman]

To the top

[Mark75H]

The "Power Dome" combustion chamber used a bump in the head, commonly called a "pad" to increase the compression a little and reduce the "end gases" much like a "squish band" in a looper head - less of the fuel/air charge is shaded from the spark plug in a side pocket created by the deflector part of the piston.

The spark plug postion is also moved to accomodate the improved combustion chamber shape ... if you have a pair of 76ci's one being an 800 and the other an 850 it is easy to see the change from the old style to the "Power Dome"

The same cylinder head changes are found in the 60 & 75 hp Scott-McCulloch of the same years .... coincidence or industrial espionage - you decide ;)

[T2x]

Ratbo's correct, it was the DR800. I found it interesting that the 800 wouldn't have it, while the 1000 in 62 still did. I've got several of those 61 cowls without the pull mechanism or hole.

Possible reason for no pull start on a DR...if you had the distributer turned 180 degrees....(Reverse)....you might lose an arm during ignition.....although Sam refers to a pullstart on his earlier DR.... maybe those models had a few "accidents"?

T2x

[Mark75H]

I think they just over estimated the quality of starters and batteries and had to put it back on

[outboard bob]

Here are 3 1960 Merc DR 800's that i have with no pull starters. They are all original except that someone painted them black. They have the chrome Mercury lettering also. The other is a 1960 merc 700 DR that is also original and has the pull starter and the Mercury lettering is decal .

[Juggernaut]

1973 I6

[Mark75H]

OK, here we go

1957 Mark 75 2 7/16" bore X 2 1/8 stroke 59.4 ci "Marathon" AJ carbs 6 individual transfer port covers
1958 Mark 78 2 9/16" bore X 2 1/8 stroke 66 ci "Super Marathon" KA carbs 3 "siamesed" transfer port covers
1960 Merc 800 2 3/4" bore X 2 1/8 stroke 76 ci (no block name) large crank splines KC carbs
1961 Merc 700 Full Gear Shift large crank splines 66ci "Super Marathon"
1961 Merc 850 " 76 ci PowerDome (on back only, no name on side)
1962 Merc 1000 2 7/8" bore X 2 1/3 stroke 89.6 ci "Tiger" First all Black Merc
1966 Merc 1100 2 15/16" bore X 2 1/3 stroke 93.5 ci "Panther"
1968 Merc 1000 2 7/8" bore X 2 1/3 stroke 89.6 ci "Typhoon"
1968 Merc 1250 2 7/8' bore X 2 9/16 stroke 99.8 ci "Typhoon"
1970 Merc 1350 99ci Direct Charge (no block name) cradle type starter mounting
1972 Merc 1400 new bolt pattern (no block name)

[raymar]

The name cast in the starboard sides of the 62-69 Merc 1000 and the 66-67 Merc 1100 was "Tiger". (The exception was the 1969 1000 Super BP, which said "Typhoon")
The name "Panther" was used on the starboard side of the 4-cylinder Merc 650. :eek: ;)

[raymar]

Let's not forget the 90 cubic inch Merc 850 (62-64) and the 90 cubic inch Merc 900 (1965) & Merc 950 (1966-1967) :p :D

[Mark75H]

The name cast in the starboard sides of the 62-69 Merc 1000 and the 66-67 Merc 1100 was "Tiger". (The exception was the 1969 1000 Super BP, which said "Typhoon")
The name "Panther" was used on the starboard side of the 4-cylinder Merc 650. :eek: ;)

Early 65 hp 60 ci 4 cylinders share the 2 7/8" bore X 2 1/3 stroke of the 89.6 ci Tiger, but the 60 ci 4's have no name cast on the block (there was no similar block to confuse it with when it was made). Panther is on 62 ci 4 cylinders because they share the 2 15/16" bore X 2 1/3 stroke with the 93.5 ci (Panther) six - same name with the same bore and stroke, just a different number of cylinders.

I'm pretty sure all 1100's are 93 ci Panthers and that if you have a 1100 with a Tiger block, you have mixed parts.

Later 66ci 4's (80's and 85's) have "Super Marathon" on them like the 66ci sixes.

[raymar]

I have had several 1100 blocks, both 66 & 67 year models and all had the
2 15/16" bore. I also have a 66 year model now with 2 15/16" bore. All had the "Tiger" name on them. (and no,they were not overbored 1000 blocks)

:)

[Mark75H]

The Tiger/Panther thing has been confusing me for quite a while. I thought I had it figured out with the Panther 62ci 4 cylinder. Now I have no idea at all which 6's say Panther.

But I did figure this out: if a 1969 1000 block says Typhoon it is a consumer block too. The 1000 Super BP was based on the no name 135 Direct Charge block, you can't change a Typhoon into a Direct Charge.

[raymar]

You are right about the Typhoon blocks. The 1000 bp was only based on the direct-charge 1350 type block. My mistake!!:eek:

[Jeff_G]

To confuse this more I believe Mercury also named some of it's small motors with the same name, Typhoon, Tiger etc.

[Tom Smyth]

So why does my 850XS say " Marathon" on the side?

Smytty

[CrayzKirk]

I've got a '66 1100SS that has been in the family since new. Tiger on the block, not Panther or anything else. Was given another one with a serial 12 digits higher and it is a Tiger. That goes for the other two scattered in my garage... The two 1250s I've got have Typhoon on the block. The 1350s are blanks. The casting is very different; no real place for the name. Porting took over that area.

Every 89.6 ci block I've seen has Tiger on it as well. I'm confident the 1000SBP was a totally different critter from the standard motors. Caged crankpin bearings, different sized journals, etc. Sounds like a real screamer. The 950/1000/1100s were so similar that I can see the guys at Mercury putting a different sleeve in the casting for the 1100 and then the 650 without changing anything else.

Kirk S.

[OldMercsRule]

Hi Guys, Great read! I just bought a 1967 [+] short shaft six that starts and runs and shifts fine in the yard (with even compression on all 6 cyl). It has the Merc 1000 decals in all the right spots, (my guess is some one swaped all the metal housing items with all the decals on them at some point in the past). The serial # is 2211156 which could be a 1967 950 or 1100. It has the trigger fired Thunderbolt switchbox, (not the point fired 1966 [-] switchbox). I have a very nice 1969 1000 #2484636 short shaft that I will put next to this motor next spring to compare the two to see if I can tell any noticable difference between them, but from a distance (based on memory) they look very similar. The block has the "Tiger" name on it, and some numbers stamped on the head that don't seem to be serial #s. I understand that the 1000 and the 1100 had KC7A carbs and the 950, (and also the 900) had KC6A carbs. There are some numbers on the front, (float housing), of the carbs. Does anyone know how to tell the KC7A carbs from the KC6A carbs? I looked for a confirming serial number stamped on the top of the block as my SELOC manual indicated would be there and could not find it. At this point (since I allready bought the motor) this is just a mistery that I would like to solve, either a 950 or 1100 would be good for the boat I am repowering so I plan to freshen up all the weak parts, (mainly wiring and gas lines), from my other parts motors, change the fuel filters, pumps, plugs and the water pump and see what she does on the back of my boat. I hope one of you tower experts can help me solve this mystery. Thanks, in advance. JR

[CrayzKirk]

The serial number can be found where the two halves of the block join together. Just look along the block line on either side around the middle of the block. Some of the later motors have the serial number stamped on the distributor mounting boss. My 1970 1350 does anway. The casting number on the block will tell if it is an 1100/1000/950. Don't know it right off the top of my head. Go to one of the online parts places and lookup the block. This seems to work for the older models in my experience (pre 1973). Dump the Seloc and buy a Mercury manual. You'll be glad you did and your motor will thank you.

Kirk S.

[OldMercsRule]

Hi Kirk, Thanks for the post. I will check for those numbers on the block when I get home tonight. I have a 1967 650SS parts motor that I killed several years ago, a beautifull 1968 1250 short shaft with power trim that just became a parts motor, (this is one that lost #3 with a hole in it, [thanks to my 19 year old son with a heavy hand on the throttle, or maybe the age and hours on the beast did it in], after running hard and very reliable for 18 years that I owned it, [carbs were still "virgins" believe it or not]), a great 1969 1000 short shaft that looks and runs like new, a 1979 115 with a 20" shaft, and a 1981 115 ELPT, and this motor (950/1000/1100) makes four running "Towers" and two parts motors, (one being a Tower). Which Mercury manual would you recommend I buy? I have an old "Glenn's" and two fairly recent Selocs. One of the Selocs covers all of the sixes that I own. I am comfortable with minor matters like water pumps, starters, plugs, wiring, fuel issues, (carbs and pumps), power trim matters, cables, control boxes, etc., but I would be reluctant to crack the case and actually rebuild one. If my 1250 were a 1350 like you have, I would be tempted to rebuild it, (I undersatnd the 1250s, [non BP] were prone to weak rods/wrist pins and were touchy over 5200 rpms, [nick named: "grenades" by one of my old Merc outboard racing friends]), the later 100 ci 1150/115/1350/1400 were less prone to overrev problems. I had a 1976 150 hp tower that I had to rebuild and learned that the pistons of the 150 hps were a little wild for today's fuels, so I put in 140 pistons, (that Tower has been sold). Thanks again for the help, can't wait to check for those numbers on the block. JR

[sho305]

In the mid/late 70s (always forget the year, '76 or 78??) Mercury changed to lower compression pistons and recommended earlier engines switched to them also. Far as I know the '73 up inline in 140/150 and '83 up 115 (that is the 140/150 but prop rated) can spin 6K rpm all day long. If I recall correctly they have the same reciprocating assembly of the XS that runs at 6400 and is often raced up to 7K rpm with little changes for the extra rpms. Naturally a stock standard inline will not make much power over 6K anyway, and a lower rated HP not over 5500. I ran my '73 1500 at 5800-6000rpm and that seemed to be the sweet spot, one prop I tried at 6400 and it was significantly slower, and 5400 was much too low. Shortly after getting it I was told from here to use premium and 40:1 and I did. Don't want to run much timing advance either, that was lowered also my Mercury. My block looks to be virgin, the fuel pumps were when I got it that must have been in '01 or so.

[CrayzKirk]

I'd get one for the early vintage inlines (66-74) and one for the later 75 & up inlines. They show up on eBay all the time. I'll have to dig one out and give you the part numbers. Mercury still has them for sale, I believe...

The rotating assembly on the 1250 is basically identical to the others. The rods out of a 1968 1250 look slightly thinner than the later ones however I think the killer of most 99ci motors is a weak cooling system or dirty fuel system. I've got a dead 1250 with a hole in #1 cylinder top and a live 1250 with a scuffed up #3. #3 is usually the first to go because it makes a bit more power and runs a little bit hotter than the rest of the cylinders.

The later 115s don't like to spin quite as easily with the slightly restrictive 8/10 reed system and possibly slightly lower port timing to give the motor a little bit more low end grunt for pulling up skiers on the family boat.

Kirk S.

[CrayzKirk]

Nothing too hard about rebuilding one other than finding a machine shop that will touch the blind bore block. Dropping the crankshaft assembly with the six ring compressors into the block is interesting the first few times. I tinker and with the help of people on this board, I took a pile of badly abused parts that was a 1350 and turned it back into a reliable motor I use on my own boat.

Dropping the timing a bit also helps the older motors deal with the lack of octane and additives intended for automobiles running on the road not old two strokes buzzing across the water...

Kirk S.

[Dave S]

Dave S. will be milling and Cuting crank cases and reed blocks too raise the comp on these old dogs. Try .040 head mill if ya will. Also ports to match. Going UP anyone?:)

[Mark75H]

Nothing too hard about rebuilding one other than finding a machine shop that will touch the blind bore block.

I don't think there is anyone better or cheaper than Bill Ruck. Bill will also pull tricks like off center boring to keep you down a rebore size if possible.

[CrayzKirk]

I had a guy that would do that; offset the bore to keep it on the first oversize. Would use pieces of a coke can to get the block totally square on the boring bar. He retired and no one in my area will touch one. When I show it to them, they give me that "dead trout" look and I just walk away...

Here are the Mercury Part numbers on the service manuals:

C-90-68647 1966 thru 1974
C-90-86134--4 late model

Kirk S.

[ssmith007]

I had a 1976 17' Kona with a 1976 1500xs on it. I loved that motor and it ran great. Do you guys think that might have been the best of the production inline 6's? It pushed that hull to around 60. When I first got it it had an extention between the mid and the lower. I added a manual jack plate and took out the extention. I think I picked up about 3mph Just doing that. It looked like a kit of some kind. 22p chopper 6000 rpm =approx 60? At least that's what the speedo said. Most of the time I ran it with a 20p turbo prop that turned about 6300rpm about 57mph? I'm still kicking myself for getting rid of it. Love the thread. Keep up the good work guys. Smitty.

[OldMercsRule]

Hey Kirk, Thanks for those manual #s I will start looking to make a purchase. Also: SUCCESS! I found the serial # last night thanks to your post: it was on the flange that the starter bolts up to. The # is 2575523, (a 1969 1000 short shaft), Great!!!! My other 1969 1000 was built a little earlier in the production run then then this one, but it looks like new. If there is still a wire tag through the stud holding the crank case together does that mean she's still a virgin, or do some shops put those wire tags back on? I guess someone swapped motor brackets previously which seems a little strange to me. Thanks again, it's great to know I now have a matched set. Love these old Mercs! JR

[sho305]

The XS and J blocks were the fastest, but only on light hulls, very light. They ran a little higher rpm and made a little more power at the expense of losing a little low rpm power. My '73 1500 20" ran a 20p laser right at 6K rpm, that should be 48-50 from a prop calculator and I filed the leading edge for lower rpm if that matters. The all new speedo said 55mph. That was a 17' checkmate with no pad and open bow, 930lbs hull. If I had the time I would get it lubed up and take it to the lake as I now have a GPS, see what it really does. But the steering cable is not good either. From what I have read here a 17' hull better be a light one for a XS, as that is the max they like to push. Many like the newest mid 80s up 115 I6s as they have the same power as the old 1500/1400s and a better ignition, as far as a normal inline. The collectors are buying the XSs now.

[SportJ-US-1]

Both of my XS' would turn 7000+. But I tended to keep the play boat around 6500. The race boat motor was always propped for 7000 to 7300 (would turn 7400 max even with only a load wheel on. The only problem I ever had was when they took the lead away and tried to get cheap and use a lead additive, instead of buying the really stuff. Took out number 3 within 3 minutes for putting the foot on the floor. Went to 100LL AV gas and never had another problem. Ran 27° advance and that was fixed, I did not move the dist., only the throttle valves in the carbs. Mains were fatter by 2 and the idle mixture was at 1 1/2 turns instead of 1 1/4, that was all the changes I made other than feeding the stock fuel pump with a blue Holley pump regulated at 4 1/2 psi. 1978 was the year Merc switched to the low dome pistons, because my 1977 race motor has high domes in it and 5 of the pistons are from the factory and still in standard bores.

[OldMercsRule]

Burp......I mean bump.

Me Buds on iboats were lookin' fer this thread. JR

[Xcelerator]

I had a quick question that I don't think was asked or covered, what is the difference between the merc 850 1962 powerhead and the 1963 powerhead as 'detuned' goes? Also what is the difference between that block and the 100hp block? Any port changes or just carbs,etc? Thanks for your time, Shawn

[Mark75H]

A 62 850 is 76ci, a 63 is 89ci (like the 100)

Probably just carbs and adjustments, but I wouldn't take it to the bank ... you could always go to one of the parts list sites and see if the blocks have the same part number

[Dave S]

The 90 cid Merc 850 used smaller carbs. Block the same. Reeds were different.:cool:

[ironlake2]

How about you guys getting together and write a book on the development of the inline 6:s all the way to the final one which I believe is the t2x.

[Mark75H]

No need to write it, its here ... welcome to the new media

[SCT]

TTT for a great thread!

[WillDiver]

Sticky? put it next to the V6 saga.

Will