Sputtering at heavy throttle....

[bullsnot]

I have a strange problem that started to pop up towards the end of last year and has gotten worse this year. The boat starts and idles great. When the weather is cold I have no problems. When the weather gets hot though I have a problem with major sputtering at heavy throttle. I can punch it from idle and it will get up and go for a few seconds but about the time I start to plane it starts sputtering badly and if I don't back off the throttle it will die like its fuel starved. Whatever the problem is, it is getting worse. The problem used to be very intermittent but has grown into a very consistent problem to the point I can't really use the boat anymore.

The boat is maintained by the book and all service such as tune ups, filter changes etc have been done this past spring. At first I thought maybe the fuel pump was dying but generally it seems when a mechanical fuel pump goes it just stops pumping fuel altogether. I also thought maybe it was a fuel pick up issue but I have 2 fuel tanks and it's doing it on both. The hotter it is outside, the worse it gets. Any suggestions?

88 Bayliner Ciera 2450 5.7L OMC

 

[bruceb58]

Hook up a fuel pressure gauge and see what it tells you when you get your sputtering condition..

Could also be a float level issue.

 

[alldodge]

Agree check fuel pressure (4 to 6 psi), and will also say I think your pump is going out

 

[jimmbo]

Sounds like a vapour lock or a percolation problem. symptoms are very similar even thought the causes are kind of opposite, except heat is involved. Hot fuel flashes to vapour much quicker when hot. Vapour lock - occurs when the fuel on the low pressure side of the pump vapourizes, the pump can't pump vapour and the engine dies from lack of fuel. Is there a fuel filter between the tank and the fuel pump? Pick up in the tank could also be clogged.
Percolation occurs when the float in the carb opens the float valve and hot fuel in the fuel line under pressure basically boils as it enter the carb and overwhelms it and the engine floods and dies. Todays fuels are being blended to function in pressurized fuel injection systems, not old fashioned carbs