Merc 2003 25hp 2 stroke, sad 😢

[nola mike]

Got the above engine. Not performing as it should. Compression 60 psi in both cylinders. Did a leak down and got 30-35% in both cylinders, though not sure the relevance in a 2 stroke. I'm surprised it's running. Still hits 26-27 mph (previous 28-29), and able to pull kids on skis (not without some effort). I had an overheat last year, but don't remember if the performance dropped before or after. Next steps? Don't know if I warped something, blew hg, or if it's just carbon, etc. I'm thinking pressurize cylinder and spray water around head? Run some snake oil to try to knock some crap off the rings? Suck it up and rebuild? Anything major will wait to off season.

 

[racerone]

There are covers on the sides of the block.----Remove and have a look at the pistons.----Post pictures.

 

[flyingscott]

Get a different gauge. Highly doubtful it would run much less pull a skier with 60 psi. I would be looking at the plastic bits.

 

[nola mike]

Get a different gauge. Highly doubtful it would run much less pull a skier with 60 psi. I would be looking at the plastic bits.

Yeah I know, I'm surprised. Gauge reads 150 on my 4.3l. 35% leak on a 2 stroke seems excessive, and only places to lose air is rings and hg, right? Which plastic bits?

There are covers on the sides of the block.----Remove and have a look at the pistons.----Post pictures.

Covers covering what? Is that in the manual somewhere?

 

[flyingscott]

On the side of the block are 4 covers on the intake side and 2 on the exhaust. Remove the CDI box and find the covers there. If there is damage it will be on the exhaust side. I would once again question the gage. Every 4.3 I have had is between 160-190 and should be at the higher end.

 

[racerone]

I don't think there is a head gasket on that motor.-----Serial # of the motor ?

 

[flyingscott]

2003 should be a blind bore Mercosil block. No head on that.

 

[James R]

If you do need a rebuild don,t try machining Mercasil.
Best to bore and sleeve or replace the block.

 

[flyingscott]

If you do need a rebuild don,t try machining Mercasil.
Best to bore and sleeve or replace the block.

Not true at all. Mercosil can be bored by a competent shop. And rebuild kits are readily available.l.