#2 Cylinder low compression, what to do?

[thresher15]

I posted this a while back:
http://forums.iboats.com/showthread.php?t=287419&highlight=toast

I just got the motor checked by another marina and the #2 cylinder is coming up 45 PSI, the rest between 100 and 108 after they put all new o-rings and put it back together warmed it up and tested it.

This engine starts, idles and runs fine. Is it possible to nurse this engine for a season running extra oil, lower rpm's etc.? There is just no money to do anything, even though they will rebuild it for $2100. I am bumming

 

[tashasdaddy]

Re: #2 Cylinder low compression, what to do?

confused who put new rings in? i would want some warranty work done.

 

[F_R]

Re: #2 Cylinder low compression, what to do?

I don't understand, did the marina fix the compression or not? Don't attempt to run it with 45#. Whatever is wrong with it will get worse and possibly total the whole powerhead out.

 

[slikciv99]

Re: #2 Cylinder low compression, what to do?

I'm a little confused. From the pics in your previous post, it appeared to be a ring problem. Are you saying that the mechanic put new rings in and you still have low compression? Did he say whether or not the cylinder was scored and needed work? You mentioned in the other post that you score in the cylinder was enough to catch a fingernail. If that is the case then a new ring would help the compression but not fix the cylinder wall. I would not run it. Running it like this would probably void any work that the mechanic did already. I still don't understand why a mechanic would do cyclinder work and put it all back together and give it back to you knowing that it still has low compression.

 

[KurtG]

Re: #2 Cylinder low compression, what to do?

I know nothing about motors; hence reading here. However, the rings he was referring to previously replaced the term most use for head gaskets. I believe that one doesn't have a gasket.

They're not piston rings

Obviously, it wasn't a head gasket-ring problem

 

[Dhadley]

Re: #2 Cylinder low compression, what to do?

As mentioned, those motors don't have head gaskets. You're going to have some piston damage as well as wall damage. I'm shocked they put the head back on. I'd sure find out what caused that before running it. It'll only get worse.

 

[james williams]

Re: #2 Cylinder low compression, what to do?

As mentioned, those motors don't have head gaskets. You're going to have some piston damage as well as wall damage. I'm shocked they put the head back on. I'd sure find out what caused that before running it. It'll only get worse.

I agree.That piston IS all eat up.If you hone it now you might can save a rebore later.If you run it any at all,all h-ll is getting ready to break loose.

 

[thresher15]

Re: #2 Cylinder low compression, what to do?

I told them to put new O-RINGS (not piston rings) on and recheck the compression to see what i was dealing with. In my previous post a few folks suggested (based on the pics I posted) I could put new o-rings on and run it. I wanted to see what the compression was with new rings. They did NOT repair the motor.

That said, can I nurse the engine for one more season or is she going to blow or whatever? It starts, idles and runs like a top. What is the reliability of a rebuilt motor? !@#$%^ , I wish I had money for a new engine. Or a new block. Or even a rebuild. This sucks. I honestly don't know what I will do without a boat. Thanks for letting me vent:redface:

 

[DJ]

Re: #2 Cylinder low compression, what to do?

I told them to put new O-RINGS (not piston rings) on and recheck the compression to see what i was dealing with. In my previous post a few folks suggested (based on the pics I posted) I could put new o-rings on and run it. I wanted to see what the compression was with new rings. They did NOT repair the motor.

That said, can I nurse the engine for one more season or is she going to blow or whatever? It starts, idles and runs like a top. What is the reliability of a rebuilt motor? !@#$%^ , I wish I had money for a new engine. Or a new block. Or even a rebuild. This sucks. I honestly don't know what I will do without a boat. Thanks for letting me vent:redface:

DO NOT run it. It will not heal itself and most likely will completely destroy itself.

The reliability of a rebuilt engine is as good as the person that rebuilds it.

A good one will last a L O N G time.

 

[jonesg]

Re: #2 Cylinder low compression, what to do?

Do it yourself.
Get a few tools, get a factory manual and pull the powerhead, have it honed and fitted to a new piston/ring set by an outboard machine shop and re-assemble it yourself, save a lot of money.

Most of us here aren't marine techs, a few are , and the guidance they provide allows many to repair and rebuild outboards that otherwise would be lost to parts sales.

 

[Dhadley]

Re: #2 Cylinder low compression, what to do?

You'll need a new piston so have it bored. The piston cost is the biggest part of the cost per cylinder. Honing until it's "clean" will most likely bring the cylinder dimension to or past the .004" wear tolerance. And it probably won't be round.

The cost between boring and honing only is minimal. Not worth the minimal savings and effort to have a "rebuilt" motor that's already wore out.

 

[CaptRoob]

Re: #2 Cylinder low compression, what to do?

You'll need a new piston so have it bored. The piston cost is the biggest part of the cost per cylinder. Honing until it's "clean" will most likely bring the cylinder dimension to or past the .004" wear tolerance. And it probably won't be round.

The cost between boring and honing only is minimal. Not worth the minimal savings and effort to have a "rebuilt" motor that's already wore out.

i agree with D. if you have cylinder scoring that can be seen and felt it's time for a rebore. go 1 oversize on just that piston. honing is just for light resurfacing not a cheap way to rebore as the cylinders will likely loose there shape.