89 force 125 re ring question

[89capriforce]

i have just bought my first boat and it is a 89 bayliner capri with a force 125 motor. i have been having some trouble with the speed on the boat it just cant seem to get over 25 mph and it takes a while to get that fast so i started trouble shooting it today and found that #3 cylinder has very little compression. i have been looking at they cylinder through the spark plug hole and the best i can tell the cylinder wall is smooth. i have seen where some people have found that the head gasket was causing the compression to be low. so tomorrow i was going to pull it apart and see if its the gasket or rings. my question is how hard is it to re ring this engine


thanks for any help.

 

[Frank Acampora]

Re: 89 force 125 re ring question

Low compression on one cylinder can be due to a bad head gasket, broken top ring, stuck rings, or a melted piston.

After removing the head, if the head gasket is good then the next likely cause would be a broken top ring. These engines seem to be prone to break the semi-keystone top ring.

Often, though, the broken ring will pop through the top land making the piston useless for further repair. You will immediately see either a bent top land or a melted piston.

Replacing rings or a piston is relatively easy. With the head off, remove the carb and manifold with the reeds and unbolt the big end of the rod through the opening. Push the piston and rod out through the top of the block. Account for all 16 rollers and both cages.

Now, since the wrist pin is pressed in, if the piston is damaged you would be better off buying a used piston, rod, and ring assembly on the auctions. It takes a special tool to correctly remove and re-install the wrist pin without damaging parts. To re-install takes a bit more work and patience but it is not "difficult"

 

[jerryjerry05]

Re: 89 force 125 re ring question

Working on these motors is not that hard.
If it's been in salt water it will be a bit harder to disasemble.
I have a good piston if needed?
I don't like to just do the 1 piston repair.
I like to re-ring all the cylinders.If one is bad how long before another goes?J

 

[89capriforce]

Re: 89 force 125 re ring question

well took the head off today and found the top ring land was broken and the piston was pitted like it was melting. so i need a new piston. the cylinder wall doesnt really look bad i can probably hone the cylinder and it would be fine.
well for right now i am probably going to just do the one piston and do all of them over the winter. i guess i don't know i might re ring the other ones too.

 

[Frank Acampora]

Re: 89 force 125 re ring question

Is the piston pitted or is it dented from the broken ring bouncing around inside? There is a difference. Pitting is due to a lean run and carb problems MUST be corrected. It will show a relatively clean piston and possibly some bright melted aluminum.

Denting will affect both the piston and the head. The piston will appear normally carboned and oily, and darkened on top.

 

[89capriforce]

Re: 89 force 125 re ring question

well the head looks fine but the piston looks beat up pretty bad. looks like this motor has ran this way for a while.
it could have been from a lean condition but i have went through the carbs since i have bought the boat. motor was like this when i got it.

 

[89capriforce]

Re: 89 force 125 re ring question

Ok guys thanks for all the input. Well the piston was jacked up from the broken ring and piston. I have ordered a new wiseco piston and rings with new upper bearing. Going to just replace the one now and when winter comes I will do a complete overhaul. If someone knows what are torque specs for head and carb manifold? Thanks again. Maybe after this I will be able to go faster than 25 mph and get there faster.

 

[Frank Acampora]

Re: 89 force 125 re ring question

70 inch pounds for manifolds and 225 inch pounds for head bolts (dry). Actually, I use anti-seize regularly and have yet to strip threads at 225 inch pounds.