Motor Starved for Gas When Idling

Eric Ferrenbach, Collinsville, Illinois: "I've put up with this problem for several years and I'm hoping you can give me some advice. I have a Sprint Fish and Ski with a 150hp Johnson outboard (1999/2000?) and I've had this problem since I bought the boat new: The motor seems to be starved for gas when idling. It only happens after the engine gets warmed up, normally after we've been out running, gone slowly through the no-wake zone (without a problem), and then parked it at the dock while we have lunch. When we come back out we have a hard time keeping it running. It will begin to sputter and usually dies when we put it in gear. Pumping the ball helps a little bit but doesn't solve the problem. I've tried to uncap the gas tank thinking it may be some sort of venting problem, but that doesn't seem to help either. When the engine is cold it idles just fine. Any advice would be appreciated."

Well, my first thought is that the engine is really ticked that you aren't inviting it for lunch! You can begin some diagnostics by pushing in the primer (key) when the engine starts to falter. If the RPM pick up and the engine runs okay, then you've properly diagnosed that the engine is starving for fuel. At that point you can go to the dealer and ask him to reset the floats, or re-jet the carbs, or even look for an air leak when the engine's warm. I just fixed one where the throttle plate assembly behind the carburetors was warped just a tiny bit and allowed the engine to run lean (60-degree OMC). Start with that and see where it goes.

Starved for Fuel Revisited

John Jefferies, Fresno, California: "I have a 3.0L Volvo Penta engine in my 2003 Chaparral 180SS. In early June of this year I had the starter motor replaced under extended warranty. Ever since that time, the engine has quit between 3700 and 4200 RPM. When it backs off to around 3500 RPM, it starts running perfectly again. The mechanic at the Volvo Penta authorized dealership insists that there's no correlation between the starter problem and the current condition. I've checked the starter wiring against my shop manual and find no problems or incorrectly installed connections. I've checked for cracks in the distributor cap and the coil, checked the coil wire and spark plug cables and can find no problems. The distributor seems not to have a condenser inside, which was suggested as a possible problem. The points are okay and not burned or scorched. I've replaced both fuel filters (in fuel pump and at carburetor) and added a stabilizer to the fuel tank that would deal with any water accumulation. The engine just seems to be starved for fuel or spark in that narrow RPM gap. Help!"

The dealer is correct, there is no correlation between the starter problem and your current situation. If it were mine, I'd go to the source, the fuel pickup in the tank, and check the filter screen and the anti-siphon valve, both of which could cause your problem.