Fuel problem help???

[jstaguy24]

I have a silverline boat with a mercruiser 470 motor. Have had it out half a dozen or so times this year. Occasionally it would stall when going from idle into neutral and a couple times it stalled when accelerating from an idle. I would get close to planing out and it would stall. After a couple trips it seemed to improve. So I thought maybe things were clearing up from sitting. Today I started having the same issues. One time on acceleration it stalled and would not start again. I pulled the fuel line off and siphoned some gas into the carburetor and it would start briefly. Pulled off the fuel filter and cranked the engine. I got no fuel coming out of the pump. I got towed to the dock and brought it home. This evening it still would not start. Poured a little gas from a can into the carb and it started and stayed running just fine. It was probably the hottest day I have taken my boat out. Over 100 here today. Don't know if I was vapor locking? Pump Is bad and losing prime? Maybe I need to re route my line. Any help would be great. Don't want to go to lake Powell with any underlying issues. Thanks

 

[NHGuy]

Re: Fuel problem help???

How about checking your fuel filter(s)? There will be a screen at the carb fuel entry point, plus hopefully you also have a fuel/water separator. That would be between the pump & the carburetor. It usually looks like an oil filter cartridge. Replace it. If you want to check the contents dump it out in a glass container and give it a few hours to settle. Once it has set a while you can see trash and water if they were in the separator. And if there is any thing but good fuel keep changing the separator every so often till it checks out clean.
If it's really vapor lock you can prove it, try the pump check when it's cool, if the fuel flows you may want to take steps to get you fuel temps down &/or flowing more easily. If there are no more than 2 - 90 degree elbows in the fuel line that's a help. Also check your fuel line condition. It should be good firm rubber. Not too hard & not too soft. If it's old, dry and hard a crack may let air get sucked in by the pump.
Remove the fuel cap when the engine won't run and see if it pumps gas then. If so clean the tank vent. If it's just too hot run the motor at idle or high idle for 3 to 5 minutes after it has worked hard, you can also run the bilge blower at that time. If you don't need the motor cover down you can leave it open to allow more air to cool the motor and fuel after running. The motor stays hot for over 90 minutes after a shut off, and it stays warm a lot longer than that.
I removed and cleaned out the anti siphon valve in my tank by spraying carb cleaner in it and exercising the little check ball with a hard plastic stick. Before you take out the valve it will probably be a pain to get the fuel line off. If there's enough line just slit the line and cut it back the 5/8" you'll need. If you need every inch of fuel line you might need to get a 90 degree pick to wiggle the tightly fitted rubber line off the tank barb on the end of the anti siphon valve.
When you go to remove the anti siphon valve use a wrench on the tank fitting plus a wrench on the valve, don't just torque against the tank fitting, that can break your threads at the tank.
ps. disconnect the battery while you work, be safe.