Mercury 240 EFI stalls at full throttle

[ctc1111]

I have a 2001 Challenger 2000 with the 240 efi M2 jet drive. I bought it used a couple years ago and has ran great and been a good boat to me. Last year towards the end of the season I was heading down river and everything was going fine. I was at about 3/4 throttle maybe a bit more and the engine just quit and would not restart. We anchored and waited awhile while we tried thinking of possibilities of the problem. Once we let it sit awhile, it restarted and ran ok but when I reached full throttle again it just died. We then limped back many miles at almost idle.

I then tried changing the inline fuel filter, and the larger fuel/water separator which didn't change the problem at all. And I think the engine sounds like it is running rougher at low rpm. Not rough as in its going to die, but just louder and has more of a rattle type of 2 stroke sound to it. This could be because I've never driven around with the engine compartment open until I started having these issues or it could actually be louder. Either way the sound just doesn't sound overly healthy.

I put the boat away for the winter and just took it out yesterday. It started right up no problem, idled fine, and wasn't smoking any more than it will on occasion. I started driving it faster and faster until I was at WOT which usually reads about 55 or so on the spedo, I could only get going about 40 - 42 yesterday. Then the thing died exactly how it used it. It wouldn't start again until we let it sit for half hour or so. I also noticed that since I've owned my boat it would smoke more than I would like if I idled for a long time and that doesn't appear to happen anymore. It smoked a little bit when I reved it up for the first time of the season, but not much at all.

So, to summarize the symptoms are:

1. Engine dies at WOT
2. I believe the engine sounds rougher when I listen to it throttle up or idle with the cover open.
3. I have changed the inline fuel filter and the fuel/water separator with no difference.
4. I am not able to reach top speed, can only get to about 40mph on the speedo.
5. The boat doesn't seem to smoke as much as it used it when I idle for a long time.

What should I be checking first? What are some possibilities of the cause? And no, I don't have a service manual yet.

Also, the one other thing I just thought of is that before this started happening, my throttle cable broke and I had to replace it. I did drive it after I changed that and before this problem showed up and it was fine. But I thought I would mention in just incase there could be an affect on the throttle position sensor or something.

Thank you for any assistance in this matter and I look forward to being a part of this forum, I'm glad to have found a site geared towards our seadoos!

 

[johnhibbs]

I have a challenger with the same engine. 240EFI M2. One of the problems I had was that the engine would die at WOT. After a lot of trouble shooting I found out that the exhaust hoses had delaminated on the inside. The engine pumps water through these exhaust hoses to cool things down. The delaminated hoses would dam up the water and block the exhaust. Try squezing the exhaust hoses. If they feel soft then you need to replace them. You can also run a test. Open the engine lid and watch the exhaust hoses as you WOT. Mine would expand like a ballon because of the blockage.

I would also suggest replacing the temp sensor on the engine if it has never been replaced. Port side temp sensor p/n 13536A14. It solves some other unrelated problems. It will improve starting when the engine is warm and will give you better gas mileage and better engine performance and less smoking. It costs less than $40 and is easy to replace.

 

[ctc1111]

Thank you for the response. Its funny you mention the temp sensor because I had heard that recently as well so the other day I did replace it. At the same time I also replaced the spark plugs. I then brought it out and cruised around 4000-4500 rpm and everything was ok. Then I got up to 5500 or so and cruised for about 2-4 minutes and then it the rpm's just started dropping and the engine struggled to stay running and it died out. Its not an instant thing all the time. It just slowly (over the course of 20-40 seconds) died out. Almost like someone shut off the battery and the efi couldn't keep going.

When you talk about the exhaust hoses with water pumping through them, you are talking about the two large diameter black rubber hoses going into the exhaust cans correct? Is the delaminated hose your profile picture? I will check this out, I kind of remember those hoses being noticeably soft when I grabbed one.

 

[johnhibbs]

Yes, those are the exhaust hoses. That photo on the left is the inside of the hose when it is cut open. SeaDoo had a recall on the hoses because they came apart and salt water would leak into the engine area and cause the linkage to fail.

 

[johnhibbs]

Here is the recall notice: http://www.tc.gc.ca/eng/marinesafety/debs-obs-equipment-recalls-mercury240-689.htm

The salt spray came from the exhaust hoses which weren't recalled but should have been since they caused the problem.

 

[ctc1111]

Thanks for the help, ended up replacing exhaust hose!