Exhaust Water sheen

[Jacob Wenegrat]

Hello,

Continuing on with troubleshooting our atomic four. Let me describe what we are currently seeing.

Engine starts easily, sounds smooth, steady. Discharges some sort of petroleum sheen on the water as soon as the exhaust water starts running. Some blue smoke on start up (I assume this is just from the choke).

Runs well, pushes a Cal 29 (8000 lbs) to 5 - 6 knots at 2000 rpm (12 x 6 prop). When revving up from idle it tends to plume smoke (whitish) but smoke steadily diminishes while running.

So that's where it stands. On the one hand glad it's running consistently, on the other hand, not terribly happy about spitting out oil (or gas?) on start up and acceleration.

Recent changes to the engine include adding electronic ignition (is it possible that screwing up timing could lead to this sort of problem?), new carb, and new valve springs.

One addition that may not be related: The engine is quite happy running at 2000 rpm and will stay at 140 degrees, but when pushed beyond that (~2200 rpm) the heat will start to rise quite quickly, I'm not entirely sure how high it would go, because I start to throttle down around 170 - 180.

Thanks as always for your help and advice,
Jacob

[Don Moyer]

Jacob,

The sheen on top of the water behind a boat during start up is usually nothing more than a small collection of oily crud that collects in the water lift muffler during actual operation of the engine. The tendency for crud to collect in mufflers is increased by using the engine only in short increments (never being run long enough to really clean out the combustion chambers and exhaust system), rich fuel mixture, poor timing, and (of course) poor compression. In your case, in the face of otherwise good performance, I assume your compression is at least adequate and not part of the problem.

I'd recheck the timing the next time you're warmed up and operating at your normal cruising RPM. Simply loosen the distributor hold-down bracket and slowly rotate the distributor one and then the other to find a location of highest RPM.

A rich fuel mixture would be indicated if your plugs are consistently dark and sooty. If this is your situation, you can read about one cause of richness in the first technical note on our web site at moyermarine.com. If you determine that you do have a rich mixture, another way to lean the mixture out would be to install an adjustable main jet.

Don