powerhead swap 1150

[laganiere]

hey everyone,
I have a 1978 mercury 1150 with a melted number 3 piston, can i use a 1976 1150 powerhead to replace it and use everything else from my 1978 ie: carbs, dist., fly wheel? the only thing the 76 comes with is the head, no flywheel, no starter, no electronics at all. Is everything interchangeable, like stator and the complete ignition setup?
power head on the 76 has 150-155 psi across the board, which was better than my 78 before i melted the piston.
I plan on rebuilding water pump, carbs and fuelpump, as I am not sure exactly what caused it. would that be sufficient, or is there anything else i should do

Serial number on 78 is 4859xxx
Serial number on 76 is 4236106

 

[monk-monk]

Re: powerhead swap 1150

Yes, everything will interchange

 

[laganiere]

Re: powerhead swap 1150

great is there anything else i should do when i put it back together? other than what i said i was going to do.

 

[Faztbullet]

Re: powerhead swap 1150

Yes, replace the trigger as that what caused the first failure..

 

[Chris1956]

Re: powerhead swap 1150

Damage to the #3 cylinder is caused by lean fuel mixture, lack of fuel, overheating or over advanced timing. Adding link and synch to your list should cover everything. I have never seen a distributor trigger cause a failure, however, you might inquire further from Fazt.

 

[laganiere]

Re: powerhead swap 1150

trigger was replaced last summer just before timing was reset. Coud the running rough be from the 3 poiston being out and me not knowing it? That would explain why even after cleaning carbs and timing it wouldn't sound right. My best guess is it was way out of time when I had it on the river at wot and it was running lean. How does a trigger cause a fire if it is timed out?

What about these backdrag carbs, i heard to shove a BB in the hose running on top of the carbs? could that have been my problem, they make your engine run lean at mid range or somthing?

Thanks again guys

 

[Chris1956]

Re: powerhead swap 1150

Folks do not like the backdrag carbs. I never had an issue with mine however. Ther are supposed to lean the mixture at mid range to top end. They do this by pulling air out of the top of the carb bowl, via the small hose into the engine. The backdrag jet restricts air being pulled into the carb bowl, therefore creating a partial vacuum. This vacuum leans out the air/fuel mixture.

 

[arsenalpsu]

Re: powerhead swap 1150

You might want to add a good decarb of the new, old block. Just to make sure those rings are good and free before you fire her off.

 

[laganiere]

Re: powerhead swap 1150

what would you guys recomend using for a decarbing agent. and what the best way do do it, should I put it in through the plug holes and let it sit, or crank the motor a few times over a few times, then let sit. For how long?. the block i am geting has 150-155 psi across the board, but I wouldn't mind doing it just to be safe, that and the fact theres ice on the lakes so I have the time to do it.

 

[Faztbullet]

Re: powerhead swap 1150

Anytime you see #1 or #3 fail on a belt driven dist motor and failure is piston crown erosion or aluminum throw off its a bad trigger. A overheat or leanout will not cause erosion without effecting other cylinders. So if #3 is lean so will be #4 as same carb feeds both, as for backdrag just remove the jets as this will richen circuit up.