The plot thickens!
I've changed the fuel/water seperator filter element, as well as the low-pressure fuel filter in the engine. See http://www.navagear.com/2007/07/explori ... al-camera/ for some pictures.
Didn't fix it.
Then I was reading in my service manual about the CTP ("closed throttle position") switch, and it said "If CTP switch has failed, engine will tend to stall when decelerating". Bingo!
Yesterday I took my multitester to the boat to check its function, and it seems to work fine: ON when the throttle is closed and OFF when it's open. Since I only experience the stalling problem when the enngine is hot, I decided to run the boat. With the cover off the engine, I let it run at the dock. Still no problem, CTP switch still functioning properly.
So I decided to take it out and run it at higher rpms for five or ten minutes, duplicating the conditions that have been consistently producing stalls. Went out, ran around outside the marina. No stalling. So the problem just fixed itself, then? Weird.
OK, this is where it gets good:
So I put the cover back on the engine, ran around a bit more, throttled back to idle, and the engine started working harder and harder until it stalled!
THE COVER! Tried it twice more, and sure enough, when hot, it won't idle with the cover on...and if you pull the cover off before it stalls, it will recover and idle just fine.
MY THEORY: exhaust that is supposed to exit the engine completely is, instead, ending up inside the engine enclosure, thus oxygen-starving the engine. When running faster, enough air is stirred around, perhaps due to the motion of the boat through the air, that the engine runs OK.
Anybody have experience with this sort of problem?
I've changed the fuel/water seperator filter element, as well as the low-pressure fuel filter in the engine. See http://www.navagear.com/2007/07/explori ... al-camera/ for some pictures.
Didn't fix it.
Then I was reading in my service manual about the CTP ("closed throttle position") switch, and it said "If CTP switch has failed, engine will tend to stall when decelerating". Bingo!
Yesterday I took my multitester to the boat to check its function, and it seems to work fine: ON when the throttle is closed and OFF when it's open. Since I only experience the stalling problem when the enngine is hot, I decided to run the boat. With the cover off the engine, I let it run at the dock. Still no problem, CTP switch still functioning properly.
So I decided to take it out and run it at higher rpms for five or ten minutes, duplicating the conditions that have been consistently producing stalls. Went out, ran around outside the marina. No stalling. So the problem just fixed itself, then? Weird.
OK, this is where it gets good:
So I put the cover back on the engine, ran around a bit more, throttled back to idle, and the engine started working harder and harder until it stalled!
THE COVER! Tried it twice more, and sure enough, when hot, it won't idle with the cover on...and if you pull the cover off before it stalls, it will recover and idle just fine.
MY THEORY: exhaust that is supposed to exit the engine completely is, instead, ending up inside the engine enclosure, thus oxygen-starving the engine. When running faster, enough air is stirred around, perhaps due to the motion of the boat through the air, that the engine runs OK.
Anybody have experience with this sort of problem?