1998 Nissan 50 hp 2 stroke compression issue

Mac300

Cadet
Joined
Nov 23, 2018
Messages
6
I have a Nissan 1998 50 2 stroke my son just acquired that has issues. No history on the engine but this is what we have determined. The motor had a oil reservoir so the oil and gas did not have to be mixed but it has been bypassed and has a "standard" direct fuel oil supply to the fuel pump now. The main fuse was blown when we got it. We got it cranked but no water was coming out of the pisser. Pulled the hose and it was stopped up. Cleared the line and it had water flow. Fair amount of white smoke. Did a compression check and had 70lbs on 2 cylinders and 90 on the third. When I pulled the plugs all were milky around the base (water in combustion chamber?). Pulled the head and cylinders are scored some and top of heads are milky. There was not an obvious place that I could see on the head gasket where it failed. I tested the spark and it was weak but that might have been a bad ground on my tester. It cranks and runs fine but obviously has issues. It is not on a boat so I have no idea how it does under a load. I'm no mechanic and most of my experience is rebuilding carbs, replacing impellers, fuel delivery, etc. I've never gone into a motor before so I don't really know if the scoring in the cylinder is really that bad or normal wear. I guess my main questions are why the low compression...blown head gasket or the scoring? Where would the water in cylinders be coming from? Is it usually pretty obvious if the gasket has failed? Don't see any evidence of cracks in the block when it is running. No obvious warping. Any input or guidance is appreciated.

thanks
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,033
It is rebuild time.----Check availability of parts first.----Scored cylinders will only get worse.
 
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