I am using a fuel tank that is reliable and has always performed well. Gas is fresh.
Yes, I did pump primer when it cuts out. No change.
Checked spark with tester. 3/8" jump, no problem.
Have not examined impeller or T stat. Will do that, however motor pumps water well and you can see when Tstat opens, as flow begins to take place at top of exhaust leg.
Other notes: Compression is 125 on both.
Fuel pump is fine, diaphram's fine.
There is ALOT of wet oil residue, inside the upper bypass cover/ intake chamber and upper crankcase.
Top plug is also oily. Switched plugs=same. Switched out hv coils=same, switched out driver coil=same.
I have had two pro marine mechanics examine this motor. Have chased every suggestion.
I think the best clue of all is the oil in the upper crankcase and intake chamber. Lower is clean,clean,clean. That wet, black oil should not be there. How does it get there??? Isn't that backflowing from combustion?
Rings look good, as seen through exhaust and intake chambers.
Is that the upper seal failing? It's dry at top of block. Engine idles great. I thought seal failure was most pronounced at idle.
One other weird thing: when warm, at idle, when choked, motor picks up speed instantly, for a few seconds (5) and then will begin to choke out. Usually, in my experience, choking a warm motor will instantly reduce rpm. It really goes for it. I have never seen that.
I have looked and listened for external crankcase leaks. No luck.
When an ignition goes dead on one cylinder, will it result in wet/black oil residue deposited on the intake side? Any opinions?
Is it possible for a driver coil to fail on only one side? Driver energizes both hv coils, alternating from one to the other. Points, condensers are new. Wiring has been checked and checked again for shorts to ground intermittent etc.
Getting ready to deep six this one.