I have a 99 centurion direct drive 315 hp merc. After spending hours on the lake. If I let it sit on the shore for a hour it will start and back fire die ect. even if I raise the engine cover while its sitting it won't run. If I start it and feather the throttle about five times it will run without any problems So is this a vapor lock or another problem ? of course it's a 105 degrees out. and the fuel pump is running. Thank You Joe

I had a similar problem recently, and I probably have the same engine. I have a 2000 315 hp merc. I contacted merc, and they said there have been problems with this recently. They pointed to the increase in the use of ethanol around the country as one of the problems. That did not end up being my problem. The symptoms you listed above lasted for a few weeks, and then all of a sudden, the boat wouldn't start. I did get it to start occassionally, but it would not run real long. I popped in a new fuel pump, and the boat has done great ever since. That being said, I offer this caveat. I have not run the boat in intense heat since changing the pump. Some people told me that if you remove the cover from the fuel pump and shoot it with cold water, this will help to overcome vapor lock. Next time the boat won't start, take off the cover and put your hand against the pump while someone is cranking on the key. If you can't feel the pump working, I'd say your pump is going out on you.

I used to have an Indmar that basically did the exact same thing you are describing. On hot days it would vapor lock after it sat for 45min - 1hour after being run at operating temp. I used to do the feather the throttle routine and it would sputter and back fire until all of a sudden the engine would take off and then it would run fine. The back firing can't be good on your engine, not to mention the wear and tear on your starter. So, I finally figured out that all I needed to do was cycle the key on and off several times with out turning over the engine (I'm assuming you have EFI). If I lifted the engine cover I could hear what sounded like someone trying to suck that last little bit of liquid out of the bottom of their fountain drink with a straw each time I turned the key on. After four or five times it would sound like the frugal beverage consumer would finally be rewarded with a steady flow of liquid. Once I heard that, I would turn the key all the way to start and voila, the engine would start and run fine. I don't know if this will help you, but give it a try.

Same problem with my Indmar except mine would start and die about 4 times until it would run. I run the blower a few minutes after shutdown or prop the cover about 2" and no problem.

Having this same issue on my 06 Indmar LCR 320. Talked to the dealer about this and he also said that it is more than likely the ethanol that is being used in even the top tier fuels now, 10% blend. It sounds like is what is happening is that the fuel sitting the in fuel rail starts to form a vapor and eventually the pressure builds up and holds a check valve to the fuel tank closed. There is no place for the pressure to bleed off, as it it not allowed in marine engines. <BR> <BR>One trick that he suggested, was to wet a towel and ring it out so it isn't dripping wet, lay it on the fuel rails for 30 sec to a min to cool the fuel down a bit. Every time I have done this the engine fires up ok. <BR> <BR>Sounds like some options are a more robust check value or an additional fuel pump. If anyone else has heard of solutions for this issue please post!

I spent some time on the phone with a merc tech, and he said to idle the boat a little bit before turning it off. He said this would allow the temp to come down. Not sure if this would work, but he suggested it.

I dont have a wake specific model but my 2001 EFI 5.0l merc was diagnosed with this and merc had my mechanic add an additional fuel pump inline with the other one (I believe its inline). The symptoms for me would only show in the winter here in Fl after running for a while then stopping for 30-45 min. After the additional pump we have never had the problem again.