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Power head removal 76 merc 115

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Oldboatguy8911

Contributing Member
I have a 76 merc 115 I recently discovered I had water spewing out of my #4 spark plug.. After further investigation I have discovered my #5 cylinder is cracked badly. Luckily! I have a spare merc thunderbolt with all of its parts.. My question is.. Should I set the spare up and just fix it, or should I just do a power head swap? Very put out with this whole situation but I am a boat enthusiast so I am not just gonna sit the boat and leave it.. So I have a spare merc thunderbolt 115 do not know why it has Been sitting up or what is wrong with it I got it with my purchase of my 76 procraft. I have been usin the spare as a parts motor.
so either swap the power heads, or put my starter on the spare and turn it over an check for compression before I do anything??

What are some things you guys would do first and check for ?
 

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Swap the power head. That much of a leaker has had to have been cooked pretty bad.


I assume you'll be doing an impeller change BEFORE firing it up? If you find any missing vanes from the old impeller, you'll HAVE to be sure they aren't hiding in that exhaust adapter plate below the power head.

Jeff
 
Ok sounds good, so unbolt everything off the motor, strip it down to the block , now I'm curious, do I have to take the foot off to take off the power head? , I have never done anything like this I'm guess nig it would be a wise move to purchase a manual . Also with this power head swap I will have to redo timing and what not
 
The foot does not have to come off, but you need to check/ change out th eimpelller in any case. Oh, in removing the power head, and don't forget to unbolt the shift from the sliding deal on the left side (as I do now and then. Ugh!)

Jeff
 
Cool thanks fastjeff! I know the water pump works! It pees with lots of force, but water had been rushing over the back end of the motor it did a hard shut off twice because of that, I believe this is when it all happend! This is also a good time to do a carb rebuild!!!
 
i think what you have is a leak from the waterjacket cover on the head.is water coming from out of the cylinder or from around the spark plug.check that gasket first.
 
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