Vapor lock or Sensor issue?

[Ruger761]

My boat has doen this maybe 3 times total. We run it for a few hrs. Then sit for a few hrs floating. Get back in starts right up. Take off goes bout 20 seconds and starts to sputter and dies. Then wont start back. Pull the flame arrestor off and the injectors (throttle blody injection 350 mag) are not injecting any fuel. Kinda give it a sec cranking on and off. Finally start injecting again and then runs perfect the rest of the day. I got boat this spring 215 hrs on it. Changed fuel filter out and only running non ethonal fuel in it asince I this spring. Any ideas? Its almost like a vapor lock issue but I didnt think fuel injection could do that?? Was 110 this weekend and lake water felt like a bath tub, but motor temp stayed bout 160

[Ruger761]

Or do you think it could be a check valve in the tank sticking causing it to only pull gas out of the filter then die on me?

[dstixs5]

Ruger -
Im actually having the similar issues in my 1999 pre2200wt however my engine is mpi - Ride for a while then park for 30-45 minutes. It will restart then die and finally will not run. When the issue occurs, Im finding my fuel/water separator to be on 1/2 to 3/4 full and the fuel system is unable to prime itself. If I top off the filter with fuel to prime, it will start immediately and I can go on my way. I use ethanol free fuel as well.

I suppose it could be your anti-siphon valve on the tank, however in my case, I checked and replaced this part with no change. My orignal looked great but I was trying the easy fixes first.

Mecruiser has a couple of options if you are truly experiencing a vapor locking problem. A boost pump(862264A7) and a check valve(862271A1). Im not sure these apply to your motor but they likely do. The boost pump kit installs inline between your tank and water separator filter. The check valve installs on the cooling hose between the thermostat housing and fuel cooler to prevent the backflow of hot water into the fuel cooler after the motor is stopped.

I've tried the suggested Mercruiser fixes as well. Idling for 5 minutes after a ride, opening the engine compartment, running the blower, etc. None of these have worked for me.

I have read others posts on this and other boards. They can likely offer more thorough responses. Some have tried the boost pump without success but many report this resolves it. I was just sharing what I've found during my research. I personally will be having my fuel system checked out before I purchase either of these items. I can work around until the end of the season.

Best of luck finding your resolution.

[dstixs5]

here is the service bulletin that acknowledges the possibility of vapor locking - including EFI and MPI engines and testing proceedures to confirm.

http://www.boatfix.com/merc/Bullet/99/99_07.pdf

[Ruger761]

Well makes me feel a little better that they have a possible solution. Thanks so much for the service bulletin. I will have to do some testing/fixing see if I can get it to stop doing it.

[giers]

I had similar issue on my 2002 20i, for me it wasn't fuel at all. It was a low oil pressure switch.

[Ruger761]

Doesnt the alarm go off when its the low pressure oil switch though?

[BLEEKER1]

VAPOR LOCK

I HAD THAT PROBLEM ALSO AN IT WAS A SIMPLE FIX WHEN YOU TURN THE BOAT OFF GAS RESIDULE SITS IN A LITTLE BOWL IN THE GAS LINE WHEN ITS HOT THE GAS VAPORIZES AND THE ELECTRONIC PUMP CAN NOT PUMP VAPORS. ALL I DID WAS TAP THE BOTTOM OF THAT LITTLE BOWL AND PUT A RETURN LINE BACK TO THE GAS TANK SO THE FUEL RESIDULE RUNS BACK TO THE TANK AND DOES NOT VAPORIZE

[Ruger761]

Bleeker

What bowl are you talking about. My boat doenst have a fuel bowl of any kind. Has line from the tank into the fuel/water filter, then to the pump and fuel cooler to the throttle body.


Last night pulled the siphon valve out. I could blow through it but the new one I had was a little easier to blow through. So put it on as a place to start. Was surprise how easy it was to get the back apart. Only 2 screws and tape on the blower hose.

[Ewok]

Some threads a while ago had people with vapor lock from heat buy they figured out if you pour cold water on one of the fuel pumps or fuel lines it got the fuel back down to temp and stopped the vapor lock.

[Ruger761]

That would do it for sure. Its only done it a few times but hate that it does it at all. My old 77 carb did it quite a bit but started up a lot faster when it did it. So Id like to get this one where it doesnt do it, which may be dreaming. And ideally where I dont have to open the cover at all that way my less experianced drivers wont have any issue when pulling me.

[TeamAllen]

I do three things that has kept it from reoccurring on my boat. Use Marine Sta-bil in every gas tank. Run the blowers to reduce air temp inside engine compartment and allow the engine to idle after making a run. I can actually watch the temp gauge drop as it idles for about a minute. I just got back from a week at Lake Powell, which is at altitude and has 100+ temps. Not one issue.

[Ruger761]

That would be a nice easy solution to try. I'll try that see how it does before doing too much work on it.

[TeamAllen]

The strange thing is I never understood why the temp gauge fluctuates at all. I would think it would remain constant?

[Ruger761]

I think its just do to the temps the motor sees when under load vs idle. Plus your velvet drive heats up more when under load, and the water goes through the transmission cooler first before it goes to the fuel cooler into the engine and out the exhaust.