Narrowing down the cause of a "Low compression" cylinder

[naghani]

Fellow boat enthusiasts,
I have a low compression cylinder (from 4). It's cause can be any of: Broken Ring, Bad Valve, Carbon residue, Bad gasket, Not smooth cylinder or ?
Can anybody help with a link/resource on a step by step process to find the problem?
With such process, I can start from easiest step and if it was negative, then move on to the next step. I dont like to start by disassembling power head.

Thanks
nozar

 

[roscoe]

Re: Narrowing down the cause of a

Re: Narrowing down the cause of a

How low is the compression on that cylinder?

First, examine the sparkplugs for signs of water intrusion.

Second step is to try to decarbon the powerhead with a couple cans of Seafoam Deep Creep or Mercury Powertune.

If that doesn't loosen up the rings, The next step is to remove the head.
Need to remove the head to examine the cylinder, piston, rings, and head gasket.