1999 2 stroke 25 hp spitting unspent fuel out the exhaust

[islander9]

I have been trying to find out why the engine is spitting unspent fuel into the water behind the engine. You can see droplets behind the engine while it is idling. Prior to this issue the engine had been been very severely overheated to the point it melted the oil tank. The idle speed is slightly low and I am assuming a cylinder(s), are being effected by the water intrusion.

I have been assuming water is getting into one of the cylinders, although I can not see a wet plug to verify this.

So far I have cleaned the carbs, replaced the spark plugs, replaced the head and exhaust cover gaskets. I can see a constant spark on each cylinder while monitoring it with a timing light, so not expecting a spark issue.

Compression is 135, 140, 135 on this 3 cylinder engine.

I have a new base gasket and before changing it on spec, I was hoping to get some advise on if there are any other places that can allow water to get into the combustion chamber (s)? I know OMC's can commonly allow water into the cylinders through a bad base gasket, is this also a possibility with this Yamaha?

My biggest fear is a possible cracked block that I cannot see.

Any suggestions would be appreciated.

 

[Sea Rider]

Were all the mentioned changed gaskets torqued by hand, torque wrench ? Independently of the method used will need to retorque them again as will have given way a bit after some hours use. Torque them back to specs, if with a torque wrench much better.

Happy Boating

 

[islander9]

Thanks and yes torqued with a torque wrench. The engine has not seen any hours since replacing the gaskets.

Also forgot to mention that I can see the carbon has been removed on the exhaust side of the bottom cylinder more so compared to the rest which has lead me down this path of water getting in. On spec I have started on the base gasket replacement.

Beyond a cracked block is there anywhere else water has been known to get in (not so familiar with Yamaha's).