Engine Stalls at idle or low rpm at start

saabmbab

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May 27, 2016
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I just bought a 2000 Sea Doo Islandia jet boat with a Mercury 240 EFI engine. Fuel injection. It starts up for a couple seconds, then it stalls while in idle. I can get it to stay running, but I have to get it off neutral and put it into forward or reverse and accelerate, giving it gas. Once it gets going, the fuel sensor beeps... after riding it for a while, the fuel beeps stop. I can ride it for a while, but when I idle it or stop and try to start it again, it will stall out again.

It's happened 4 out of 4 times I've been on the water this year. Very scary when you have a family with small kids out on the water.

I've taken it to the mechanic. First time it died, he found a cracked starter mount. I got it welded back on then I took it back out of the water. The same stalling problem happened again. The mechanic found a split vacuum line and replaced it. I took it out a 4th time today and it happened again. Same problem. Starts up, runs fine for a while. We stop for a bit to enjoy the lake. When we start it up again, it stalls at low RPM. I can get it going as long as I rev it a bit out of neutral. But you have to be moving. Huge problem for us, when we stopped in a marina for lunch. We couldn't get out without crashing other boats. It was terrible.

What could be wrong with this? I hope I didn't buy a lemon. Thank you for your help.
 

saabmbab

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Thanks AllDodge. The engine is fuel injected. I don't think it has a carb. Do you think something else needs to be cleaned?
 

saabmbab

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Thanks All Dodge. the mechanic is suggesting it might be the sensors. What do you think?
 

alldodge

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Your post stated fuel in it

What beeps are you getting?

4 beeps then 2 minutes off and it repeats (water in fuel)
Continuous intermittent beeps (throttle position sensor)
Other kind

What sensor does he want to replace?
 

saabmbab

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It seems the beeps change a bit.. it's hard to hear with the motor. The last time it was multiple beeps in a row, then it stops. Starts again, then stops. After driving it a bit, the beeps go away. Is there a computer readout on that tells you what's wrong on my engine? When I have a car problem, there are diagnostic tools. Wondering if there is the same here.

Of the 4 times I've gone out, it only stalls at start up or at low rpm/idle. It's pretty consistent. Works at cold start, drive for a while. Shut off engine. Then it gives me a problem after restarting it while on the lake for a bit and warmed up. The TPS notes I've read suggest it can stall at any random speed.
 

alldodge

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According to the list it should only be water in fuel, low oil or throttle position sensor
 

alldodge

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To verify parts I could use a serial number of the motor,
 
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