Merc 125 stacker

[largecar91]

What are the differences in the production 125 Merc powerhead and the 125 stacker?(aside from the stacks). Were the pistons different, porting? I just got a couple 125's and want to make a stacker. :confused:

[Mark75H]

In 1968, no difference.

In 1969 the block was basically a 135hp type "Direct Charge" block with 1250 type starter mounting brackets.

Merc factory race motors of that era were blueprinted to the extreme. To get a motor close to a factory racer of that time period you'd have to have a dozen or more running motors to disassemble and reassemble to make one super motor.

I'd say you'd also have to already own a set of stacks at this point. They are about as coveted as a 1956 Mark20H racer and harder to come by. If you don't already have the stacks, your pockets better be deep ..... $2k - $6K probably.

There were specially prepaired motors for certain members of the Merc racing team with major modifications ..... but they are completely impractical for even a display model. Since there is no actual competition for such a motor, there is no reason to do anything to your motor to make it harder to start, more likely to self destruct and unlikely to push your boat over plane.

What boat you thinking of putting your stacker clone on?

[Dale]

I cant imagine any water in the US where you could get away with running the
stacker for more than a few minutes ;)

but maybe other states are not as strict as Tennessee

no sound like a 2 cycle with megaphones, not as much power as the expansion
pipes but definately more sound
..Dale

[largecar91]

Not sure of a hull yet but I have been wanting a set of stacks (factory Mercury) ones for a long time. Today I found my "HOLY GRAIL"!!! A set was given to me along with a couple 125's!! They are water injected(can you tell me the difference in the wet and dry stacks)? Today has to be one of the best days of my life!!(spoken like a true boat nut!) I think they will bury me with these stacks!:D :D :D :D :D

[eautosales]

You lucky dog :D

[largecar91]

I let a lot of stuff go in the past. I had a record setting T-2(still trying to buy it back) and I had a T-2 C6 and some other things that got away years ago! When my sst 120 motor becomes obsolete(probably not far off), it is going to get freshened up and put away!!

[Mark75H]

(can you tell me the difference in the wet and dry stacks)?

Tuned exhaust depends on several critical factors

(1) exhuast port open duration
(2) pipe length
(3) speed of the sound waves resonating in the pipe

Mercury made some factory team motors with such long exhaust port open duration that they significantly reduced low and mid rpm power and needed a pipe tuned to the 3,000 rpm range just to get the boats to plane off. After they got going they needed pipes tuned for 6,500 rpm.

They achieved this dual action pipe not by changing the length of the pipe as was already popular with alcohol fueled small boat racing classes, but by changing the speed of the sound waves in the pipe. At 3,000 rpm you need a pipe twice as long as you need for 6,000 rpm or - sound traveling half as fast. Cooling the exhaust gases in the pipe significantly slows the sound waves down - giving the same effect as a longer pipe.

Some PWC's use computer controlled water injection on their tuned exhaust for a wider power band. I use water injection on my modified Merc racer. A micro switch in the throttle turns the water off when I squeeze it full open.

My best guess would be that those stacks actually came off of a 1970 or 71 factory racer which would have been fully based on a 1350 powerhead if you are going for full authenticity. They should fit on your 125's just fine.

Now you need a boat capable of 90 mph and a right hand Super Speedmaster to complete your set.

[largecar91]

Thanks. I never got a chance to look at the motors. I have not picked them up yet. I think they are just stock 125 and not related to these pipes.

[Dale]

been 35 years(gosh that sounds like a long time) but in the back of my mind
I am thinking there was a jet change and timing change when you put them
on a stock motor ..

there was some posts a year ago and one of the dealers was talking about
installing the "kits" on a stock motor .. he may chime in if the post stays up
near the top a while and they were listed in the parts books if you have access
to the old books
..Dale

[largecar91]

Thanks for the info. I will see what I can find.

[Mark75H]

I am certain that Dale is correct. I may have the jet # somewhere in my archives. If you can't buy the jets, you can drill out std jets with the right drill bit. I'd be very careful with the timing .... careful, conservative testing would be a much better course rather than going by a 35 year old spec.

Optimum jetting and timing would also depend and vary greatly with the boat.

[largecar91]

Does anyone know what kind of coating is on the elbows and the stacks? I would like to redo them to look new again.

[Fish]

there was a boat at mount dora this year that had a stacker on it that looked better than new and ran (until the cops came). Might try a search of mount dora or "mzt" or "Mtz" which was the make of the boat. the owner replied on here with some info and I am sure he might be able to help you with your coating question (his stacker was one of several vintage race motors he has).
Good luck, although since someone gave you those pipes I would say your luck is pretty good already.

fish

[Mark75H]

Probably aluminum oxide ;)

[Bruster]

Does anyone know what kind of coating is on the elbows and the stacks? I would like to redo them to look new again.

Gary's are chrome plated. The stacks on the Mercury display motor are chrome. Mine were stainless steel, painted black. :eek:

[Raceman]

Bruce, are you sure they're chrome plated and not just polished stainless? (I don't know, just askin', but properly polished, stainless can look that way)

The ones that I've seen that are original and unmolsted have almost a parkerized lookin' finish on em. Not with the same green tint, but similar texture and durbility. I don't guess I know what alum. oxide looks like. Unless I'm mistaken the stacker motor that Merc was haulin' around to the shows a year or so ago had the elbows polished or chrome plated also. 'Course since it had a late model cleaver from a 4 or 6 gearcase I don't guess originality was a high priority. Will chrome even stick to stainless?????

[Dale]

>>I don't guess I know what alum. oxide looks like

not sure if you are pulling our leg(s), but Mark was pulling Largecars ;)
alum oxide = rusted alum ... not really .. just unprotected alum exposed to air

Merc wouldnt sell the BPs to us comoners, but the local dealer kept bugging the
regional rep till he finally showed us some part numbers to order the "kits"
I had just ordered a new Allison so my buddy ordered the stacker and SSM kits
for his tunnel (checkmate I think) so he could outrun me ;) I couldnt come near
affording the stackers ..

it was a complete kit, with templates for sawing out the top and bottom shells
and a new side cover , jets, hoses/etc for the water injection, probably more stuff
.. the whole kit was on a regular shipping pallet and the SSM was on another pallet
no way was I going to take a sawzall to somebodys motor, so I did the jets and
small stuff while he did the cutting .. about 5 hours after we picked up the
stuff it was on the lake screaming .. not very fast but you could sure hear
it coming ;)

I have seen the pictures on here of the stainless and polished alum elbows
but his was all allum except for the megaphones and the springs ..

spring 1970 about this time .. I can remember that like it was yesterday
but cant remember last week ;)

nothing sounds like 12 boats with stackers trying to plane off and milling
around waiting for the start gun

..Dale

[Bruster]

Bruce, are you sure they're chrome plated and not just polished stainless? (I don't know, just askin', but properly polished, stainless can look that way)

The ones that I've seen that are original and unmolsted have almost a parkerized lookin' finish on em. Not with the same green tint, but similar texture and durbility. I don't guess I know what alum. oxide looks like. Unless I'm mistaken the stacker motor that Merc was haulin' around to the shows a year or so ago had the elbows polished or chrome plated also. 'Course since it had a late model cleaver from a 4 or 6 gearcase I don't guess originality was a high priority. Will chrome even stick to stainless?????

Not sure, but the Merc display and Gary Mac's are both chrome, originals could have been polished stainless. Stainless will chrome plate just fine. What are yours? They also may have been "brite dipped" . I have friend who has a sheet metal fabrication facility and he makes stainless steel parts wash baskets for the auto industy and brite dips them to look kind of like chrome. Here is a blip on the technology.
http://www.finishing.com/307/36.shtml
There are a bunch of other coatings that were available in the 70's + the old standby aluminium bar-b-que paint. Don't laugh look at the water discharge tubes on the stackers, came straight from the local Ace hardware. :eek: :eek: :D

[Raceman]

>>I have seen the pictures on here of the stainless and polished alum elbows
but his was all allum except for the megaphones and the springs ..

..Dale

I'd have a really hard time believing that Merc ever made the elbows in aluminum. First, based on the hot look right in the middle of the turn of my stainess ones, I'm not sure they'd live with no cooling if made from alum. Second, with the vibration/reasonance, I don't think they could keep em from breaking off. Every set of elbows I've ever seen (I have 4 sets of my own) have stainless elbows. All of mine have stainless sheet metal megs, but I think there may have been some plain steel megs in the early days.

[Raceman]

Bruce, all of mine are stainless with some kind of coating. It looks a lot like parkerizing on a gun barrel, but without the green tint.

[Dale]

>>live with no cooling

where does the water injection squirt in on yours

..Dale

[largecar91]

My elbows are non-magnetic so they are either alum or stainless. The cones are magnetic, so either low grade stainless or steel. The cones on mine have an overlapping seam on them.Are the cones original?

[largecar91]

Is there a valve to feed water to the elbows or does the water dump in there all the time? I thought on Bridges site, he had some wet stacks and I saw some kind of switch or valve?

[largecar91]

Is the inner plate in the the exhaust different from the stock one?

[Raceman]

The inner plate IS different. It routes ALL of the exhaust out through the stacks. A stock one would let it go downward to the bottom of the powerhead.

The pipes aren't wet all the time. The injection, which wasn't on the earliest ones was to give the engines more torque off the corners, then they'd dry em out for more top end down the straight.

I think I remember seeing some with non stainless cones that would rust like those in the picture. I think they were early also. The VERY EARLY stacks like were put on the 75H's and subsequent engines used in racing were ALL non stainless steel to the best of my knowledge. The type I'm talkin' about is the ones that showed two pipes going into one instead of a 4 bolt elbow bolted to a side plate that did the same thing internally.

Dale, every water injected elbow that I've ever seen looks like the ones pictured, but the injection isn't usually run all the time, and NOT for cooling. In longer straightaway races, like Parker for instance I think the heat would melt an alum elbow, plus the vibration may very well break em off. If you look at the stainless ones, they have wings on both sides to prevent breakage.

[largecar91]

I know this might be a "dumb" question, but would anyone have an inner plate to sell or the dimensions so I can machine one? I looked at the elbows last night again and I am pretty sure they are stainless. The only rust on the cones is where the spring holders have been rewelded on a couple of them. Just a little light surface rust. (luckily they have been stored inside and dry all these years!).

[Mark75H]

VERY EARLY stacks like were put on the 75H's and subsequent engines used in racing were ALL non stainless steel to the best of my knowledge. The type I'm talkin' about is the ones that showed two pipes going into one instead of a 4 bolt elbow bolted to a side plate that did the same thing internally.Very early "steel" stacks were mild steel. Very soon after, when they reduced the weight of the side plates and elbows by using aluminum the megaphones were made of stainless (probably 1965 or so for Quincy, but possibly as early as 1960 for Hubbell). I have some of each of these and know this for certain. The 1964-70 15 to 60 ci Quincy Looper motors used aluminum megaphones.
In longer straightaway races, like Parker for instance I think the heat would melt an alum elbow, plus the vibration may very well break em offStrangely the elbows don't get as hot as the megaphone sections do; I don't think heat failure is an issue. Even after a 10 minute run without water injection, my exhaust elbows are not hot enough to make steam (you can touch them without getting a second degree burn) maybe 150º or so and there is no problem with spark plug wires touching the elbows, but the megaphones are very hot (maybe 600+º) paint burns off of them - any contact with the megaphone brings a blister. On the pre-1968 non factory stacks, the exhaust filler block is a machined chunk of aluminum and is usually not water cooled with no ill effects.

The spring mounted vs welded megaphone sections is an improvement to avoid vibration fatigue.

[largecar91]

Could someone give me the height of the exhaust plate. I already have the bolt pattern. This way if no one is willing to part with one then I can machine a new one. If the megaphones get 600+ degrees and if they were chromed, they would blue pretty bad. Maybe a ceramic coating like that used on headers would be the way to go for the megaphones. I have decided to make the stacks functional and I am going to try to build as much of an authentic 125 stacker that I can. I still have to go thru all my parts and see what all I have to work with. :cool:

[Raceman]

I've got one out of a motor, but not handy where I am right now. The piece is actually cast rather than machined and it'll be a pretty good machinin' job to copy it, and a pretty good draftin' job to draw it. Gohr needed one also a year or so ago and was talkin' about getting one made. You might check with him and see if he ever solved the problem.


One other thing, somebody mentioned the drawing to cut the top and bottom cowl. Since the stacks were run before my time, I don't know how they did em all back then, but it'd be virtually impossible to duplicate the wraparound. My extra setup appears to have a factory cut upper and lower pan, a modified cowl support, and the wrap. The stacker wraps are closed in the front where the stock ones open, and open at the stacks.

Sam, I was basing my heat theory on the hot spot lookin' areas right in the turns on mine. Maybe it wasn't a problem on the older 2 into one system, but all of mine look like the outside of the turn is a super hot area.

[Dave S]

The inner plate is like the stock one, you could weld flat spots to make a stock one seal. I think the tickness is the same as stock. Also some sillycone could be used. I woun't tell if any one asks. ;)

[Mark75H]

That's IF you can find someone who can weld on old wet aluminum AND there is enough base metal left to weld to. I haven't had much success with having old Merc exhaust stuff welded:( I'd like to hear if that works.

[Raceman]

Hell, it's hard enough to get inlines not to leak around the inner plate as it is, with stock parts. I can't imagine weldin' on one and trying to get it to seal.

[largecar91]

I am still trying to track down the original one that went with my stacks. If I cannot find it, I will have to see what I can come up with. I thought about seeing what I can do with the stock one. I talked to Bill Gohr tonight and he said if he had a nice one to start with, he was going to see about getting some cast. A billet one doesn't look that difficult, just time consuming. This is just a small hurdle in building this motor. The biggest one was finding a set of stacks.

[T2x]

I am still trying to track down the original one that went with my stacks. If I cannot find it, I will have to see what I can come up with. I thought about seeing what I can do with the stock one. I talked to Bill Gohr tonight and he said if he had a nice one to start with, he was going to see about getting some cast. A billet one doesn't look that difficult, just time consuming. This is just a small hurdle in building this motor. The biggest one was finding a set of stacks.

I have no doubt that someone could probably sell a dozen kits or more in very short order........ Keep us posted.

T2x

[Project Contender]

Hell, it's hard enough to get inlines not to leak around the inner plate as it is, with stock parts. I can't imagine weldin' on one and trying to get it to seal.

Use the Merc Epoxy. It worked everytime for me. Even a leaker that was built-up and ground off.

[bridges]

largecar91

Here is a photo of two stacker inner plates, you may have seen this already. One is original and one has been opened up. I will try to get some dimensions today and let you know.

I have seen standard inner plates weld-modified to work on different motors, it is possible to add to them...but the biggest difference on the stacker is the routing of the flow.

[largecar91]

Thanks Bridges. Any dimensions off an original part will be helpful. I have seen your stacker in the pictures and it is awesome!!

[bridges]

The stacker inner plate is 0.750" thick. The Twister 1 inner plate was made identical. The casting # is 53946.

Now, a standard 1350 inner plate is 0.925" thick, with the bottom chamber open. If you want to make a Stacker or Twister1 inner plate, here is how you do it: First heliarc the lower chamber up and then have the outer side of the plate plate milled down until the overall plate thickness is 0.750" ---don't worry, it still won't get into the water jacket. We mic'd all the measurements today and it will work.

If you do it, take some pics. I'd like to see it...

[largecar91]

Thanks very much!!! I am definetly going to do it! I am working on the cowling now. It looks like it will not be too much of a problem. I have another question: The rear and upper supports that hold the top cover on, are they cut down stockers or they a cast piece common only to stackers and or twister 1's? Barry

[Mark75H]

Dale was right about the jet change ....

With stacks you need .088" main jets Merc part # 1399-3907

a number 43 drill bit will drill a .089" hole

I would drill out the jets in a fixture rather than directly clamping the outside of the nozzle. Holding it directly in a vise tight enough to keep it from slipping will probably result in a larger oval shaped hole when released. Either screwed into a nut that it correctly threads into or a junk carb (use a little grease so the jet will back out easily). A junk carb lets you clamp the carb base flange and know you are drilling straight thru the jet and not at an angle (on carbs where the jet is perpendicular to the base).

I have also held the jets in my hand and drilled with a bit held in ViseGrips a few times at races to make correct sized jets.

In between drill bit size jets can be made by drilling smaller and filing with a welding torch tip cleaner, but you shouldn't have to do that on this job.

I do not know the timing change spec ..... but it would have been based on gas that isn't available any more anyway. Might be best to go down to 15º or so and work your way back up a little until the motor is lively. Best timing might depend on the boat and prop a little, too.

[Raceman]

Thanks very much!!! I am definetly going to do it! I am working on the cowling now. It looks like it will not be too much of a problem. I have another question: The rear and upper supports that hold the top cover on, are they cut down stockers or they a cast piece common only to stackers and or twister 1's? Barry

They're modified stockers. They shouldn't be hard to do, although some welding is required. I can't imagine how you think you're gonna fab a wraparound, since the stacker type breaks back at the stacks and is solid under the faceplate.

[Mark75H]

I don't think it is that hard to do the wrap. It looks like the same part just bent different and cut out for the front cover screw. Would need to find a louver punch and die for the louvers and a new set of decals.

[Bruster]

They're modified stockers. They shouldn't be hard to do, although some welding is required. I can't imagine how you think you're gonna fab a wraparound, since the stacker type breaks back at the stacks and is solid under the faceplate.

The wrap is the easy part. Take an original wrap and cut out how ever much you need less about 1/2" on each side. Fold this 1/2" over with about 1/8" gap. Fab 1/8 X 1" slats to go from the lower cowling to the upper, spaced the where the opening needs to be. Slip the wrap over the slats and attach like a standard wrap. :eek: :eek:

[largecar91]

The wrap is pretty much taken care of. I have located a mid section and gearcase. I still need some other parts and I am going to try to make it as correct as possible. I will keep you all updated. Thanks for all the help!!! Barry