Stall at Idle or low RPM at start

[saabmbab]

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.

 

[Dr Honda]

Well.... Could be a bunch of things.

1) The idle is set too low. (should be around 1000~1100 RPM in the water)

2) The port side temp sender could be bad. It's a common issue, and causes LOTS of smoke, and hard starting. Along with poor idle, and burrning extra fuel .

3) A bad TPS. (Same as #2)

4) Bad sparkplugs. It's a 2 stroke, and they need changed at least once a season.

5) Low compression. The boat is new to you... did you check it?

6) Split hoses. Since you found one... I would assume that most of the rubber under the deck lid needs replaced.


There's the place to start looking.

 

[saabmbab]

Well.... Could be a bunch of things.

1) The idle is set too low. (should be around 1000~1100 RPM in the water)

2) The port side temp sender could be bad. It's a common issue, and causes LOTS of smoke, and hard starting. Along with poor idle, and burrning extra fuel .

3) A bad TPS. (Same as #2)

4) Bad sparkplugs. It's a 2 stroke, and they need changed at least once a season.

5) Low compression. The boat is new to you... did you check it?

6) Split hoses. Since you found one... I would assume that most of the rubber under the deck lid needs replaced.


There's the place to start looking.

Thanks DR Honda. I'm going to tell the mechanic next I see him. He was saying he thinks it might be the fuel sensor. Is that what you're referring to as the temp sender or TPS?

 

[Dr Honda]

Fuel sensor? There's only 2 things that I know if that COULD be called a fuel sensor. That's the sender in the tank, running the fuel gauge... and the other is the "Water in Fuel" sensor. Either one wouldn't shut the engine off.


Personally... I would grab a meter and check both the temp sender, and TPS myself. If you get a mechanic who just throws parts at the boat, it will get very expensive. (The TPS is around $500)

 

[saabmbab]

Do you know of any marine dealers that specialize in sea doo / mercury jet engines? I live near Detroit. Thanks Dr Honda.

 

[Dr Honda]

Seadoo dealer wont' touch it. Seadoo and Merc had a falling out in 2005. Just looks for an authorized Mercury dealer. But... be prepared to bend over if you take it there. You will pay full retail on the parts. and +$125hr labor.

 

[saabmbab]

Ok. The mechanic looked again and found 2 problems glaring. He got the fuel pump to fail when he was testing today. He also noticed the water senor was removed and wasn't there. I am not about to spend $1100 on parts so I found a couple OEM on Ebay. I bought these items:
http://www.ebay.com/itm/311600361832
http://www.ebay.com/itm/111900020070

Do you think these might be the issues?

 

[Dr Honda]

The fuel pump is fine. The water sensor is a maybe. Did he tell you the module was missing... or just the sensor? The proper fuel filter comes with a new sender... and that's only $11 or so.

 

[saabmbab]

A quick update. He found a lot of metal shavings in the gas reservoir so 100% sure the fuel pump and connection was a problem. The mechanic found the fuel pump also needed a connector kit and o-ring - which added another $200+ in parts. Connection Kit - fuel, 8090901 and Oring 804086

He worked on it and found the pump was still failing. Be believes it's the computer failing. A new computer costs $2K+. He did find a way to bypass the computer by setting the ground on the engine to the fuel pump. By doing that, he said it stayed running just fine for 30 minutes with no issue. The problem is he won't use that fix unless I do it myself or hire another mechanic due to liability. Apparently, if you leave the ground connected, the pump stays on and could cause a leak and then fire. He said it should work just fine if we put a switch to the fuel pump. I'm going to add the bypass and take it back out to see if the issues are resolved. Have you heard of this?

I will also ask about the TPS to see if he found anything regarding that.