Diagnostic Help Requested

[RI Sail]

I've owned my 1979 Tartan 30 with an original Atomic 4 since August 2003. The previous owner, who evidently did little to no maintenance on the engine, advised me that there was two year old fuel in the tank and that the engine may run rough but adjusting with the choke who enable the engine to run properly. Needless to say, this was B.S. The engine was difficult to start for about two weeks and then impossible to start. A new carburetor, points, plugs and condensor enabled me to use the vessel for the remainder of the 2003 season.
When I opened the boat up for Spring 2004, there was a distinct smell of gasoline in the cabin. However, after ventilating the cabin well, the engine started right up. The engine has run ok for most of this season. The odor of gasoline disappeared. However, I kept fouling spark plugs after approximately 6 hours of use. Also, after about an hour of continuous operation, the oil pressure would drop from approximately 40 to about 10 to 15. Letting it cool down would boost the oil pressure back into the 40 range. At it's best, the engine would run at about 1250 rpm's and move the boat along at about 5 knots in light winds. Motoring into a head wind of 15 knots or more would yield about 3.5 knots of speed. Increasing throttle would only cause the engine to sputter and stall.
In late September, I had difficulty starting the engine again. However, putting in new plugs (Champion RJ12C) did not correct the problem. I'm beginning to think that perhaps the carb is fouling as well. The engine has not run in about six weeks and the boat is now sitting in my yard.
The starting difficulties are frustrating enough. However, the smell of gasoline is back. Is there a known problem with A 4's where there is a gasoline smell when the engne has not run for a period of time? I'm now also noticing small traces of oil in the bilge.
Any input/suggestions/recommendations would be most appreciated.

Joe Walkden

[Don Moyer]

Joe,

A couple things for you to consider:

1) Fuel odors frequently come from fuel dripping out of the throat of the carburetor. This condition is usually caused by the float valve becoming stuck. The questionable condition of your fuel supply would be consistent with this scenario.

2) Fuel odors also can come from a leaky mechanical fuel pump diaphragm. In this case, you should smell an odor of gasoline on the oil dip stick. In worst cases, a leaky diaphragm will cause the oil to thin, and the level may also rise, which would be consistent with a bit of oil showing up in your bilge.

3) Plug fouling can (as you suspect) result from a rich condition within the carburetor, which goes back to (1) above.

4) Your oil pressure probably just needs adjusting. The regulating valve is just aft of the fuel pump. You will need to loosen the 3/4" locking nut, then turn the threaded shaft of the valve in (clockwise) a turn or so. If the valve is difficult to access on your boat, you can give the valve an arbitrary turn while the engine is not running, and then check the result the next time you use the boat.

5) A maximum power of 1250 RPM is rather low. It can be caused by too large a prop, poor compression (less than 75 psi on all cylinders), improper timing or a very rich condition (refer back to (1) above.

Don