Blue Smoke and 2 oily plugs

[Jacob Wenegrat]

Hi Don,

In the time since last asking your advice we have changed to electric ignition, replaced the distributor cap, rotor, plug leads, plugs. Also installed a new carb, and an electric fuel pump.

After all these additions/repairs we took the boat out for a weekend of approximately 10 hrs. of motoring, and everything was perfect, engine ran better than ever.

Coming back to the boat after about a week of sitting in the slip started the engine and there was some blue smoke in the exhaust. After running for 20-30 minutes the blue smoke increased quite a bit. Removed the plugs and found that the plugs from 3 and 4 had an oily wet residue, whereas the other two plugs seemed normal. Tried putting in new plugs, but this didn't seem to alleviate the smoke.

The variation in how much smoke appears is also noteworthy. At times there is very little, barely noticeable, but then without any change in running conditions the smoke will increase to a huge plume.

Also wanted to note that oil pressure on the engine stays pretty much at 40psi, at both idle and cruising rpm, warm or cold.

Any thoughts on troubleshooting this?

Thanks again,
Jacob

[Don Moyer]

Jacob,

I'm a little confused over the blue color of your smoke. Your report of oily plugs leads one to think of an oil smoke, except for the fact that when pistons "pump oil" from stuck or broken oil rings, the smoke is usually white.

Are there any other symptoms that would explain why/how those two cylinders
might be in trouble, like low compression?

Don

[Jacob Wenegrat]

Possibly white...

Hi Don,

It is possible that the smoke is white, the exact color has actually been a subject of debate between us...

If we were to assume that the smoke is white, then would the symptoms would be consistent with broken/stuck oil rings?

What would be the procedure for fixing this situation?

Also, there is some valve noise which seems to be coming from cylinder 3 and 4. Is it possible that the smoke could be a result of poorly adjusted valves?

Thanks as always,
Jacob

[Don Moyer]

Jacob.

Thanks for the update. I'm concerned that with the valve noise coming from the third and fourth cylinders, you may have one or more broken valve springs in each of those cylinders. Broken valve springs allow the valves to "float" at higher RPM which affects compression, causes a pronounced clicking sound, and could account for your smoke. Unfortunately, I don't know of any easy way to check for broken valve springs other than to remove the valve cover and have a look.

Don