70-73 Tower Evo.

[Clams Canino]

OK evolution talk again.

1969 brought us the 125 Super BP (direct charge)

70 and '71 sold ran this motor as the 1350.

'72 saw the 1400.

'73 saw the 1500 on to infinity (more or less)

1. What separates the '72 1400 from the 1350 and for that matter the 1500?

2. Was the 1350 indeed the 125 Super BP head unchanged?


-W

[Mark75H]

You are correct that both the 1250 Super BP and Merc 1350 were Direct Charge, but part numbers of the block and pistons on the 1250 Super BP are different from all other Mercs. Could be the same castings machined differently or could be completely different castings. I don't know anyone who knows anymore except maybe Dick Lanpheer. The problem is since 1970 or so, most of the of the BP mids and lower units have been separated from their powerheads. You might be tempted to look at Merc's 1250 Super BP that they display at shows (recently the AOMCI Fond du lac show), but their display stuff is known for being inaccurate at times.


Raceman can correct me if I'm wrong, but I think the 135 fits on the same tower as the 125 and the 135 has no finger ports. The 150 has a slightly different bottom stud/gasket pattern from the 135. This accomodates a different tuned exhaust arrangement.


Mark 1976 in your notes for the first 155hp xs model

[Clams Canino]

Thanks Sam...

I'm still curious about the 135 - 140 - 150 evo from 70-73.

-W

[Raceman]

I can't shed much light on the 1250 Super BP. Although I do have one with the original powerhead, mid, and gearcase intact, I've never been in it.

As far as the others, the 70 & 71 1150 & 1350's were the first of the production direct charge engines and were identical except for reed stops and the plastic diffuser in the middle of the carb venturi's. The 1400 had the first of the new bolt pattern at the bottom of the powerhead in 72. In 72 ONLY, the 1400 and 1150 had different bolt patterns on bottom, with the 1150 being a carry over from the previous year with the old pattern and the 1400 having the new one that would carry foward with all the future inline 6's. 72 was also the only year that Merc ever built a short shaft 1150. Early in the year they said that there would be no short 1400's, but they did in fact supply them later. The 1400 was a one year only engine and was identical to the 1500 except for the power port in the piston and corresponding trouph in the cylinder wall. All the short shaft and longshaft 1400's were identical except for shaft length, as were the 1500's in 73 & 74. In 75 the short engine got the J powerhead with the higher port timing, while the long shaft engines always stayed the same. I've seen some opinions that the first J powerhead was somehow more desirable than the XS which came in 76 and continued through 78. I've never believed there was a difference. I had a new in the box J powerhead which I bought new in 75 to replace the tired upper part of my 73 shortshaft 1500/15 Allison which had been raced extensively by a previous owner. I've had an uncountable number of XS's since and if there was ever any difference I never heard reference to it at the time.

[Clams Canino]

Thanks RM for the in depth reply. I've added it to "the document".

-W

[kspradling]

Wayne,

Not much to add however here is what I've discovered from my diggings:

The 72 1400 had the high deflector pistons, no boost port, tuned exhaust and standard reed stops. The later engines got the boost port and low deflector pistons. From the service manual, I have noted that the 1400-1500 are also rated at a higher RPM range than the 1350.

I think the changes were pretty minor; tuned exhaust, boost ports and more flexible reeds.

The online parts list shows the 1250 Super BP used the standard high defector pistons. Perhaps the 1500XS was based on that design.

Just rambling as usual!

Kirk

[Clams Canino]

Well sure, we can draw a straight line from the 1250 Super BP to the 1500 XS. I was just curious exactly how we got there LOL.

I have a 72 1400 on the bench next after vacation. Though RM already explained it - I'm still looking forward to peering inside this one. :)

-W

[Raceman]

Kirk, in terms of piston DOME ONLY, the pistons were the same from the 70 model 1150/1350 until the time that Merc lowered the top of the deflector sometime in the late 70's or early 80's. All the earlier 1150's, 1350's, 1400's & 1500's as well as the XS's had the higher domes. I wish I could recall the year that Merc threw the low domes in, but it was no sooner than 76 and I think several years later than that. The domes were changed purely for durability reasons because the engines, which were borderline piston happy already weren't doing so well with the junk we were getting at the gas pumps. There were also pistons available in these configurations with only 2 rings, but I can't remember now when and on what engines this change was made. I've got boost ported pistons in both ring configurations. All my stuff is high dome. I've never owned an inline with low dome pistons, although I have seen em.

[Clams Canino]

RM I don't think this is the case... but could the change to low dome have come with the 78 1400 debut?

I know it was named such for marketing reasons only, - but the dome change at that point would make good sence. No?

-W

[Clams Canino]

Oh!

And by the way - I've yet to run into the 2 ring pistons looking at

72,75,74,84?, and 86 off the top of my head.

I'm not sure if they came in the motoers new - or were a racing aftermarket product - or maybe stock J / XS only?

-W

[Mark75H]

Looking through the BP parts lists from the era I find that all the BP's came with 2 ring pistons and, ... the original blocks and pistons had different part numbers from production motors. A little bit more sleuthing and I found that the stock 135 block and pistons are shown later as replacements for the 1250 SUPER BP block. I am not saying the 135 block and pistons were not better than the BP block and pistons, just that they were originally not the same.

Clarification of the tuned exhaust: All the inline 6's after about 1961 use internal tuned exhaust, grouping the cylinders into 2 groups of 3. All along the way there were minor internal change/improvements in the exhaust tuning. In 1972 there was a dramatic change in the exhaust passages at the base that required moving one powerhead stud out of the way.

Wayne, you need one of John Kwast's "Where Used" books for Merc part numbers. Would answer a lot of your questions.


Let me now ask this question: On the large inline 6's was the 110 the last to use the 4 reed per cylinder reed blocks and the 125 the first to use the 10 reed per cylinder reed blocks and crankshaft with beveled edges on the counter throws?

[Raceman]

Sam, Wally my friend in Fla. probably knows the answer to that, but I don't have a clue.

[CrayzKirk]

Hi,

Bought the internals from a 1250 and it has the same crankshaft as the direct charge motors. Same reed blocks, rods, etc. as the 1350. Can be interchanged with the 115-150hp. It is much different from my 1100 internally.

Just from scanning the online parts lists, the 72 1400 was the last year it shows high deflector pistons used in the higher horsepower engines. Perhaps this reflects changes Mercury made for reliability in the lists themselves. The 115hp motor continued to use the high domes until the 140hp disappeared and the 115hp prop shaft rated motor appeared around 83. It used a different reed configuration that has the thin petal 140/150hp reeds and a 10/8 configuration. Perhaps the lesser number of reeds is to keep the velocity of the fuel mixture up and prevent leaning of 1-3-5 due to gravity effect on the mixture.

It looks to me that Mercury started using the low domes in 73. I haven't openned many motors up and every crank that I've seen that uses the 150hp reeds has low domes and visa-versa.

The 1500xs show high dome pistons in all years and I believe the 850 used high domes as well.

CrayzKirk

[Raceman]

CrazyK, the reason the part number changed after the 1400 was that the 1400 didn't have the hole in the piston skirt, where all the 1500's did. If the parts list doesn't show the higher dome pistons in all of the earlier pistons, then the parts list is wrong. I've never owned or been inside a 20" 1500 newer than 75, but the change to the lower domes was definately AFTER this time and I think in the very late 70's, but not sure exactly when. The 1150 would show the same part number as the old 1400 piston because it remained without the hole for a number of years. There was some shuffling of the number of rings on the pistons back then, but I can't recall exactly when, but the dome configurations remained the same on all the 4 & 6 cyl Mercs from 1970 until AFTER 1975, regardless of horsepower.

I personally don't believe that Mercury ever put a low domed piston in any inline with 150 stickers on it, but after 75 my interest turned to V6's, so this is just an opinion.

[Bill Gohr]

Wow, what a question, As far as the exhaust tuning on the 70 and 71 they were the same except for the 71's had a divider in the middle. There was also an update kit which gave you a different water manifold and inner exhaust plate which directed the exhaust in different directions. As said the 72 1400 was basically a 1350 with the newer tuned exhaust. The only different engine which wasn't listed was the 73' long shaft 1500 which came with squared exhaust ports and this is the motor which people claim to be stronger than the J block. When we were building SJ and JP engines this was the block of choice. As far as the low dome pistons I believe that was 78. As far as 2 ring pistons of the same era those came from 4 cyl inlines and I believe some of the 3's. As far as the 5 hole reeds and beveled cranks, that came with the 100 cu.in. motors.

[Raceman]

"As far as the exhaust tuning on the 70 and 71 they were the same except for the 71's had a divider in the middle."

Bill, if that's in fact true, it's new information to me. Better description please.

[Bill Gohr]

Of what I answered 5 questions?

[Raceman]

Bill, the one I quoted above from your post...........this 'un:

"As far as the exhaust tuning on the 70 and 71 they were the same except for the 71's had a divider in the middle."

I've always thought the 70 & 71 1150 & 1350 bare blocks were identical.

[CrayzKirk]

I have a 1350 disassembled and an 1150 disassembled. The blocks are identical and the part number is identical. The reed stops are 5/16" on the 1350 and 5/32" on the 1150. My ramblings about the pistons is from the online parts listings at mercruiserparts.com. It shows two different pistons for the inline motors. The A12 is high dome w/power port and the A9 is low dome w/power port. I matched up the serial number and the years to come up with my info. MasterTech Marine has the same info posted for their powerhead rebuild kits. Since I've never seen the virgin insides of a 73-81 140/150 this could all be incorrect. I also don't have original parts lists for these motors so I can believe they have been updated at some point.

I'm wrong all the time however, I'm learning all the time, too!

CrayzKirk

[Raceman]

Kirk, what Bill's post seems to imply is that there's a difference between the 70 & 71 blocks, unless I misunderstood him. I'm certain that there's no difference between the 1150 and 1350 blocks in a given model year and was also unfamiliar with the exhaust difference between 70 & 71 that he mentions. In the case of the 1150/1350 differences, in addition to the reed stops, there was also a different sized diffuser in the middle of the carb between the two, somewhat restiricting the venturi, the 1150 taking up more space. So back then, you spent about 20 bucks on parts, a day's time and your 1150 became a 1350 and several MPH faster. (I did it to my first one)

Again, if the parts lists are showing low dome pistons in ANY INLINE before 76, they're either superceeding or incorrect. IT ABSOLUTELY NEVER HAPPENED. I don't think it happened before 78 either, but that's just opinion.

Bill, there's one other thing that intrigues me in your post on the 1500's, the mention of the exhaust port being different in the 73 longshaft motor. In that the 73 shortshaft (which many people say was made available before the longshaft in that particular model year for some reason) had a stock powerhead as opposed to the J beginning in 75, why would the block configuration have been different on the longshaft in 73 only.

[kspradling]

Ok... I'm convinced!

I'll look at the 1150 block when I get it back from the shop. I can believe the parts lists are updated. It seems odd to me that the pre 70-81 1150, 70-71 1350 and 72 1400 would be the only ones that still have the high dome piston in the parts list. I think the online list still has the original part number in it. If I get bored, I may go back and compare those numbers between the different models.

Has the original question been answered? How did the direct charge evolve from the 1250 SuperBP to the 1500? Since I haven't seen one, I'm going off the parts lists and the differences seem fairly minor; reeds, reed stops, tuned exhaust and power ported block/pistons. Doesn't seem much like evolution; simply minor changes over the years.

Thanks for the info!

CrayzKirk

[Bill Gohr]

Pistons, all the piston numbers in 78 or so superceded to low domes. I know this cause when we were building race motors we called Merc and ordered all the old numbers they had. I think when he's looking at the engines he's listed he's looking at non ported numbers only judging by the engines listed.
You are correct the difference between the 1150 and the 1350 in 70 and 71 is the carb filler, and the reed opening. The timing my have been 2 deg different or something and of course the jetting.
When I was talking about the divider in the exhaust I was talking about in the adaptor. 70's had no divider, 71's had a divider which was aluminum which burned of and plugged up the gearcase. You'd always get the complaint of no power. The replacements were stainless. Also the update kit which I spoke of is in the block. The water manifold and the inner exhaust plate. The two pieces directed the exhaust in different directions than stock which made more power. You could look at the exhaust passages and they had little deflectors on them
As far as the 73 1500 long this is no guess, The long shaft's had square exhaust ports. They looked like triple drilled. Like they drilled the port and then did the corners with a smaller mill and squared them. There is no way to tell as far as external marking that I ever new. The only way we new back then what it was, was if you had an original powerhead on a 73 long and the exhaust cover was smooth with no ribs like a 1400. This was a factory piece and could be used in stock classes. We were told this was to create more power on longs because they would end up on bigger boat applications

[Bruster]

I still am not sure.

[Bill Gohr]

a race motor why don't you show a wider pic of that. 3 intakes and they're staggered with the flat in the middle

[sho305]

So you are saying my '73 1500 is one of the better I6's? Maybe I should keep it? It looks to have never been apart by the paint on the bolts, and I think the exhaust cover-if the outside cover on cyliner exhaust-is smooth. I feel it once in a while to make sure it is full of water at the top.

When I checked the compression, I had 120-122 on all 6. Thought it was low, but quite close being 2psi apart. Then I was told the 1500 had more port timing and so lower readings would result, and my gauge is nice but old. The only wear I can see is the edge of the cav plate is shinny from water off the prop, and a very slight clink when wiggling the flywheel back and forth. Otherwise all original paint. Distrubutor rotor seems tight.

The jets are original #s, but I can't get a read off the plugs. They are clean all the time with just a carbon track. The big ridge on the piston about hits the plug and that is a darker brown color so I figure it is rich like it should be. I cut some foam away from the front cover for a little air but no difference. I only put 4 hours a weekend on it max in the summer and it sat for 8+ yrs before I got it.

I did set the timing kinda high (+1 turn from 22)and run premo for more scoot. After 7 props it likes 5400-5700rpm best for sure. 5900 slowed it right down. Any prop with a bigger diffuser kills the power big time. That 5900 was before advancing the timing, but I doubt that would change much, unless I had the wrong props. I only set timing by starter originally and not at speed, so I am not sure it was right, however it was very close from who ever last set it. It turns a LaserII 20p 5700rpm on a 17' checkmate BR, no pad, before I get to the end of the lake and have to turn (.5 mile?). Managed to get 5800 last time I ran it by going into the weeds.

Wanted to relieve the exhaust, but was recommended not to as no power increase would result, and could crack leg. Maybe I need to find a Vector for it?

[Bruster]

The S/N is 3321119 which puts it in the 72 140 S/N group, but has the old style (125) bolt pattern on the bottom. It was on a 1250 Super B.P. Mid with stacks.

[Bruster]

picture of the intake side.

[Bruster]

We need to get Crazy Horse to take a day off and drag his Hydrostream XS up to Croton or Hardy some Saturday morning for kicks. It would be cool to have 3 performance inlines together showing the V-6's how well the old inlines still run.
How well does that 150 run on your rig?

[sho305]

Well, that is the problem I have...the Checkmate is nice as far as room and heavy-duty-ness, but far from fast. I was going to (still might) redo it all. It has nice lines and handles great. Only the cost of an interior is holding me up, and the fact that it needs a big motor to go fast. It has no pad, just all vee. I can only get 55 on the new speedo, 52 on prop calc w/10%. Maybe more if I didn't run out of lake as it has not left the one my place is on. It should have setback on it too. Needs 200hp I think. Trying to find a 22/23p to try and see if it will pull it. I want to see 60mph, but I think this is too much boat for that. Another guy on here is going to put a pad on his 'Mate. My 17' says 930lbs for hull.

The motor runs great however, and pulls hard all the way up until I start loosing water. I get great air if I hit a wake trimmed that high and nice rooster too. The Laser will start getting loose even and get another 200rpm, like 6000, but no faster. I even got bitched at one day for going fast ??? just 'cause it looked like it. I would like to see it on something faster, like a vector? Not sure what way to go with it. It is rare to be out alone, and some fast boats don't like wakes so I am not sure what to look for. Not into flying out of the seat anymore, bumpy is fine. I did waste a newer 120 'Rude on a similiar boat one day, thought it would be closer.

[Bill Gohr]

I would have to say thats exactly what you said itwas. I've only seen 2 other blocks like that. Triple intakes staggered with twin exhausts. Very nice piece by the way. That probably would be the super BP. Notice the exhaust is filled on the sides for the stacker manifild, something you don't normally see on in lines

[Bill Gohr]

If you have an original 1500 long 73 that would be the good one, Sounds like it's little tired. Why don't we take it apart and show the ports and such board apparently no one has seen this. Are you going to get a "V" or what. Give me a call....847-356-3245

[sho305]

I'm trying to figure out what to do with it. I hate it when I can't figure out what to do:eek: I think I really want something faster than a straight vee, maybe 18' & 200hp to start with. Want to run some other lakes around here and handle a few waves though. Hmmm.:confused: Can I get my $$ back out of it? It needs a redo, but all the little pieces are there so it looked like a good candidate. Not wanting to trash the motor, I switched to 40:1 this year.

In fact, the previous owner swears up and down it ran 60mph, and a little over on a long lake and he ran lots of other boats at 60 even if the speedo was wrong. I don't see it at under 55 now. You think it would be close to 60 if fresh? Maybe 122psi is really low? I been told this is a heavy 930lb vee boat and no way 60mph.

It looks better with the SS Laser prop on it now. Boat is '73, motor looks up as '73 serial number. Any other way to tell? Here: 36295XX.

Check the nice WOOD jackplate:D

[Clams Canino]

As a quick note - I just got in a 1350 powerhead - seals intact.

Though it's the closest living relative to the 1250 Super BP, it seems to not use the intake port covers that that dood has been looking for all year. It uses the triangular extrusion while his was more squared off.

-W

[Raceman]

Rat, are you talkin' about the differences internally or externally on those covers?

[Clams Canino]

Internally.

-W

[Bruster]

The squared off covers are used only on the factory race motors. (experiance speaks) Remember the 1250 B.P. is a "fishing motor" on a "race" lower unit. The "Super" B.P. is a factory race power head. with different rods, reed cages, and block, along with a handful of other unique pieces.

[Raceman]

I've got a super BP with the original powerhead. One of these days I'm gonna scatter it and compare it with a 1350. I always thought they were virtually identical.

[Clams Canino]

When you do - post lots of pics. :)

-W

[Bruster]

in this thread and look at the pictures I posted of my Super B.P. block, and read what Bill Gohr has to say about 'em. I still am confused with the S/N........

[Raceman]

OleGator, I've got a funny prim-o-nishun' who you are. You been workin' on any 650XS stuff lately????

Either way, welcome to Scream and Fly. If the answer to the above question is yes..........it's about damn time.

[sho305]

Raceman, did you suck another poor soul into this addictive swirl of outboarding nirvana?! Oh shame on you!! Hehehe:D ;)

[Raceman]

Sho, I ain't sayin' who this fella is 'til he decides to come out of the closet hizseff', but I will say I been buggin' him to come play here, just like a couple of other people have, and it's gonna be fun to have him.

[sho305]

Hey that is great, welcome to S & F! If you ever wondered where the outboarders are hiding, here they are....well for sure those of us up here in the snow bank.:rolleyes: :)

[Clams Canino]

I think I might have a clue....... (I hope)

-W

[sho305]

There is some history info on inline LUs here: http://forums.screamandfly.com/forums/showthread.php?s=&postid=436368#post436368 just to connect the two posts.

[Jeff_G]

To answer a far earlier question the "modern" two ring pistons came out in the 80's as a replacement piston and are semi keystone, they were designed to combat the coking of the piston which the three square ring pistons are fond of. No motor after 73 had a 2 ring piston, except the above replacement.

[Raceman]

Jeff, I thought some of the 4 cyl 850's had the 2 ring pistons????????

[dragonwolfe]

I've got a '74 85hp Merc with 2 ring pistons.

[Jeff_G]

RM I was refering to the 6 cyl. motors. Not the little 4 cylinder. I guess they could be mini-towers :D

What Wayne was asking was the semi-keystone that Merc came out with later.
The earlier 850 was a square ring wasn't it?
The T2 motors had a 2 ring piston too. Didn't the Mod 50 motor and one of the 650's have a 2 ring also?

[Bill Gohr]

Actually you will find them in 650's as well as 850's. These were 2 flat ring pistons. They were only used in certian serial groups. You have to go back through the books and look at number of rings used to find them. These were used like 73 thru 77. Before the low domes came out. Like Jeff said, the later service pistons were all 2 ringers with 7 degree rings.