4 Stroke Heat Stroke EFI (40hp) 2003 on Bass Tracker

[dhfish]

Has this happened to anyone? I can run my motor off and on all day in 70 degree weather.Once it gets past 80 degress and up; sitting in the hot sun fishing. Then, at start up, it idles okay just briefly then badly. when I go to throttle up it dies. Then I have to troll over to the shade and sit a good while after which it starts up like it never happend. Any Idea? Vapor lock, heat exhanger problem, fuel pump, HP fuel pump? what do you think? I would like to nail it down so I don't change parts that do not need replacing.

 

[RLT III]

Re: 4 Stroke Heat Stroke EFI (40hp) 2003 on Bass Tracker

not sure about 4 stroke but 2 stroke 70 mercs that suffer vapor lock in hot weather conditions are normally due to the check valves in the pump and is cured with new ones or drilling a 0.031 hole in the center of them.If yo don't have a manual yet you should get one.Probably not much help but maybe we can get you some attention

 

[Silvertip]

Re: 4 Stroke Heat Stroke EFI (40hp) 2003 on Bass Tracker

Just a suggestion, but try letting the engine idle a minute or so before shutting it off.

 

[Texasmark]

Re: 4 Stroke Heat Stroke EFI (40hp) 2003 on Bass Tracker

Sounds like vapor lock to me too. Vapor lock is caused by the fuel pump sucking on the fuel line with restrictions somewhere in it. The harder the pump sucks, the lower the atmospheric pressure in the line and with the high temp the fuel just boils. Boiling fuel doesn't have enough BTU's per unit to support combustion and the engine dies.

I first learned of vapor lock with a '72 Chev station wagon on vacation. I had installed a fuel filter between the fuel pump and the tank because I didn't like the mickey mouse one they had at the inlet of the quadrajet carb.

Coming back from vacation one hot summer afternoon with the wagon towing the family play toy and kids and play toys stuffed in every corner, at highway speeds, the engine just died. Took a long time to get home as I'd have to let it cool down, go again till it did it again and repeated the process.

Obviously when I got home out came the bright idea fuel filter. No more problems.

Mark

 

[sschefer]

Re: 4 Stroke Heat Stroke EFI (40hp) 2003 on Bass Tracker

Check your fuel pump and primer bulb check valves. One of them is bad. When the temp rises the fuel in the tank expands and the tank vent allows the gasses to escape. This process creates suction on the fuel hose and if the check valves are bad in the fuel hose primer bulb or the fuel pump, a siphon can form and it will suck the carb and intake dry as a bone. Many four strokes also have a check valve in the fuel filter to prevent this so if you recently replaced your fuel filter with something you found at an auto parts store that could be part of the problem too.

The reason it takes a while to get it going again is because you now have air in your fuel system and it takes a little while to get it all out.

There is a trick where you put a vertically hanging loop in the fuel hose or the vent hose (if so equipped) to stop the siphon. It works sometimes.