Low compression on two cylinders in port engine

[Red323red]

I took my Yamaha 2011 242 limited s and the port engine will not go past 5 RPM did a compression check and found that cylinder two and three reads 60, 70psi. The boat has over 500 hours. I was thinking of using ENGINE RESTORE to help build up the compression. Does this sound like a good idea?

 

[14SX190]

Do a leak down and see where your losing compression.
I've become very familiar tearing down my 1800 engine these past few days.

 

[WREKS]

No. I think you have a serious problem.

 

[14SX190]

No. I think you have a serious problem.

Well, I was trying to be optimistic for him and have learned how valuable leak down testing is thanks to #WREKS
But yes, those readings are too low and engine has 500hrs. There have been some with more.
Depends on care.

 

[WREKS]

@14SX190 I was responding to the ENGINE RESTORE.

 

[14SX190]

Oh yeah
That stuff won't work for OP

 

[Red323red]

Yes out of the water the engine runs fine but when it's in the water it doesn't go past 5 RPMs. I'm thinking the leak is in the piston rings. The shop said it will cause about $10,000 to replace one engine. The boat was going 50mph when I first got it. Last year but now it goes about 30 mph

 

[MiaYam]

Yes out of the water the engine runs fine but when it's in the water it doesn't go past 5 RPMs. I'm thinking the leak is in the piston rings. The shop said it will cause about $10,000 to replace one engine. The boat was going 50mph when I first got it. Last year but now it goes about 30 mph

What did you end up doing? Im having the same issue. Thanks.

 

[David Martin]

What do the plugs on the low cyl's look like. Black carbon or oil soaked? Pictures of plugs please. The reason I ask is because fuel injectors streaming raw fuel into a cylinder can wash down the cyl walls.......washed walls (no oil) protection causes low compression and wear rings out over long periods of time.

It would take a lot of hours to damage the rings and cyl walls, lack of oil on cyl walls will lose compression and power. Any damage to 2 cyl's should show up on the plugs.