low compression ? fed up!

What usually can cause you to lose all the compression in top cylinder after just running on water ?<br />Can it be related to bearings going out/ or a pre existing knock noise from either the reed or not good lubrication through the tube to the crankshaft?<br />Its and older 4 cyl 85hp ser#3743683 and I had just had it serviced 2 times -one for rebuild carbs the other set timing,resynk and adjust carbs, replace carbon part in dist/new plug wires<br />Adjust on water.It sounded like a reed could have been going bad or the lower bearing noise when listening with stthescope-they said.<br />Im fed up with it all .The mechanic said it was possible that a plasitic ice bag may have gotten trapped in the prop that can cause overheat..<br />I dont know what to believe now..<br />Can you ever soak it down to free the piston (like in some autos)or is there no chance of reviving it?<br />Any feedback is appreciated cause I am at a loss for boats!

Re: low compression ? fed up!

The Knock is most likely a new hole in the top of a piston, or a shelled skirt.<br />You gotta figure out the problem before we can determine the cure.

Re: low compression ? fed up!

Lots of possibilities ... broken ring, lean and scored cylinder wall (although rebuilding carbs should have stopped this one), overheated and seized, lack of oil and scored, etc. A stuck ring can sometimes be freed by a decarb treatment. Once things are scored or broken, replace/repair is the only choice. There's no quick, cheap fix for those issues.

Re: low compression ? fed up!

where do you start ,and is it possible to free up the ring if stuck?

Re: low compression ? fed up!

A stuck ring can sometimes be freed by decarbing. Do a search for more on that subject. Lots of info.

Re: low compression ? fed up!

Yes, a bag sucked across the water pickups on the lower unit deprive the engine of cooling water and it will indeed overheat. Lilly pads, weeds and other stuff can also stop up the intake. Look into the spark plug holes and check the tops of the pistons. If you see a hole or pitting on the piston crown, its rebuild time.

Re: low compression ? fed up!

A catastrophic loss of the top cylinder could be a waterpump issue, or a faulty carb, or misadjusted timing. (Im assuming oil was in the gas)<br /><br />The bag thing is the tech GRABBING AT STRAWS considering he's responsible for the carb job AND the timing. I'd take it to a third party for an autopsy to see that the carbs or timing *wasn't* in play here.<br /><br />-W

Re: low compression ? fed up!

I just wet down the cylinders with lube/fluids and let it work to free the cylinder (#1 mainly) and now I can start it up fine.Before it would not seem to start or even stay running .Now it runs on hose fine even with idle bar down.<br />Why is it starting fine now -did it free up the rings?Is 120ish right on compression ,give or take 10?<br />The guy(REPAIRER) said its re timed and re adjusted/resynced carbs, .Should I have the timing and sync-carbs rechecked by another merc repairer?<br />Any info is helpful...

Re: low compression ? fed up!

Wow