Guess I will need rebuild. What else should i do while I'm buildling the powerhead?

[udoittwo]

Took a while but I was able to remove the exhaust cover plate without removing the lower cowl or figure out how to remove the shifter bracket on my 1986 75HP Mariner. I found the top cyl. is scored and one ring is stuck, so I guess after all that, I will have to rebuild.
Other than water pumps, spark plugs, and fuel line O-ring replacements, no one has ever been under the hood of this motor. With a fresh motor, what else should I replace, up date, clean/check while this is all being done?
Roughly, how much does a #A199493 1986 76 hp 4 cyl.
Thanks again,
Karl.

 

[Chris1956]

Re: Guess I will need rebuild. What else should i do while I'm buildling the powerhea

OK, you need to fix the cause of the damage to your cylinder, or it will happen again. Damage to your cylinder was either caused by overheat, lean fuel/air mix, too large a prop or incorrect ign timing.

So, replace waterpump. rebuild fuel pump, clean carbs, do link and synch.

 

[CharlieB]

Re: Guess I will need rebuild. What else should i do while I'm buildling the powerhea

Once you clean that cyl with something like muratic acid to remove all aluminum smeared off the piston. Be very careful, wear safety glasses and have PLENTY of air so you do not breathe much of the fumes. And take care not to spill any acid anywhere else on the motr, it eats alum and you only want to clean the very inside of the cyl. A small acid brush, lots of rags, and a garden hose of water to rinse eveything totally clean, dry then lightly wipe with an oiled rag.

Mic the cyl and see what it is compared to the factory service manual. If not worn you may be able to use a standard piston and not bore the cyl at a machine shop.

 

[udoittwo]

Re: Guess I will need rebuild. What else should i do while I'm buildling the powerhea

Yeah, I've worked with muriatic acid before. Nasty stuff.
I probably did the piston in on a long trip up the lake starting with good water pressure and noticed next time I started it, it was just dripping. I don't know how long I may have run like that. I changed the pump right a way and it ran well but the damage may have been done then with the stuck ring finishing it off.
No knowing anything about boat motors, the block is aluminum and the cyls. are steel sleeved? I'm guessing there is no safe/clean way to hone the cyl. if I'm not tearing the motor compleatly down?
Can the piston be serviced on the boat or will I still need to remove the powerhead?
Thanks again for the help,
Karl.

Once you clean that cyl with something like muratic acid to remove all aluminum smeared off the piston. Be very careful, wear safety glasses and have PLENTY of air so you do not breathe much of the fumes. And take care not to spill any acid anywhere else on the motr, it eats alum and you only want to clean the very inside of the cyl. A small acid brush, lots of rags, and a garden hose of water to rinse eveything totally clean, dry then lightly wipe with an oiled rag.

Mic the cyl and see what it is compared to the factory service manual. If not worn you may be able to use a standard piston and not bore the cyl at a machine shop.

 

[racerone]

Re: Guess I will need rebuild. What else should i do while I'm buildling the powerhea

There is no cylinder head on the motor.---The block must be removed from the exhaust housing.--So the motor must be torn right down.----Crankshaft must be removed with all 4 pistons attached to it.---Sorry but there no real short cuts here.

 

[CharlieB]

Re: Guess I will need rebuild. What else should i do while I'm buildling the powerhea

With the crank, rods, and pistons pulled you can get to the steel cyl liner to clean. Using only a hone isn't recommended, the alum tends to plug up the hone stones and then they can't do an nice even hone of the cyl. Get the alum out first, run a glaze breaker hone lightly then measure. If the bore roundness and taper are within spec you're good.