Merc 240hp v6 wont start when in Water but will start when out

[prostuff]

Hi guys I've been reading allstate thread on this issue but message him and no reply I figure this is an old thread but after serching the forum i could not find anything else on this problem I have the same boat with same engine and I have exactly the same issue , has anyone esle run into this and may be found a solution. I will thank you guys for any input on this...!!!

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Merc 240hp v6 wont start when in Water but will start when out


Hello everyone. I am back again.

I have a weird problem.

My 240hp v6 m2 EFI motor runs fine untill I place it in water.
I recently replaced a powerhead along with some other things as well:
Fuel Pump, Starter, Fuel Hoses and Oil hoses.

Ok. This seems weird to me but here we go.

I noticed by pure luck and after a few trial starts and boat launching that I have come to the conclusion that the motor will not start when there is a "LOAD" on it. I believe it is a water problem because when you start the motor (No water hook up - I know bad thing) it turns and fires up right away. I also noticed that when yoiu connect the water hose to it "BEFORE" you start it with the water running - It wont start. Same as when I launch the boat in the water. Then after sitting in the driveway for about ten minutes with water shut off - it starts right back up.......

Does anyone have any ideas about this?

Manual really doesnt say much about it.

Also could there be such a load on it that the back pressure is not allowing this motor to start.


Thanks Allstate ..

 

[El Toro 33809]

I have a couple of ideas, and they could be inter-related:

1) How is the battery? Fully charged?
2) Does your "steering assist" work (boat rev up when the wheel is fully turned)? If it does, try turning the wheel to the stop when cranking the engine.

 

[prostuff]

Hey toro, no the steering assit don't work.
Battery fully charge.
I just went outside and turn the key and the boat will start right up, the issue is when i put it in the water it will start an run for about 4 seconds then will stop and if you try to sterted in the water again it will crank and turn but not even an explotion and after doing this for a few times it will get flodded with gas , so to get it going again i need to pull out of the water and let it sit for a while.Now outside the water i can strted as many times as I want with no problem.Look like when starts getting water from the crate into the engine something happends.

Hey thank for the reply by the way.

 

[johnhibbs]

The only thing I can think of is that it’s the change in temperature when the water is applied. If the engine gets too hot it shuts down. Maybe the temp sensor is broken and is reacting backwards. I don’t know if that’s possible. You might try physically removing the temp sensors from the engine block but still keep them wired up and apply the hose water and see if it starts.

Or,

Maybe one of the head gaskets is bad and letting water in a cylinder. The good news is that they are a lot easier to replace than on a regular car. It only takes some hand tools and a weekend.

 

[prostuff]

John thanks for the reply. I took the boat back to the people that work on last,before I pick up the boat they said that they had run the boat at the lake for like 45 minutes ( wierd) so now lets see what they find and we agree that next time they do a test at the lake im going with them.

 

[Mayerichm]

Please let me know if you find something out, I have the same problem on my 2000 speedster. I posted in the "premium tech support" two weeks ago and got one generic reply. Mine will run fine on the hose, then just crank and crank when I take it to the lake. I don't know if it's the 45 minute drive to the water or the water itself causing the issue. Checked fuel pressure and spark at the lake and both were fine, thinking something isn't telling the injector to open.

 

[prostuff]

Likewise, sure I know how frustrating this is after I find any info from the guy's working on the boat I will put it here.

 

[Dr Honda]

That's very typical of low compression. Have you checked it?

 

[prostuff]

yes I though of that but I have like 150 on all cylinders

 

[prostuff]

One thing that I’m thinking is that I mess with the lines coming out of the baffle in the gas tank, I wonder if may be I cross one of the lines when I reconnect?

 

[jsmidkiff]

at every plug? just asking, just went through this and finally checked spark and three were not fireing. but would start out of the water..and if that is the case, you have a stop dieod bad in one of the cdm's, and normally is cylinder number one. it will be one of the one firing!!!!

 

[prostuff]

Were you able to tell that the motor was not running on all cylinders do? Or did it sound normal..!

 

[Mayerichm]

Finally took mine into a mechanic and he found that the throttle was out of adjustment. It was set to idle too low and wouldn't kick off with a load but would run fine on the hose. Now she screams... with a mild cavitation problem, but that's another story. Just food for thought.

 

[prostuff]

Happy for you dude, Great news.

 

[Dr Honda]

Were you able to tell that the motor was not running on all cylinders do? Or did it sound normal..!

There is an easy test for that. Starting with a cold engine... Run the engine for 20 to 30 seconds... and shut it down. Then... touch the spark plugs. If the cyl wasn't firing... the plug will still be cold.

 

[prostuff]

Great tip , Thank's