Yamaha F250 dead in the water

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Harpoon

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My F250 shut down just after launching. All maintenance has been performed, two fresh tanks of fuel. Boat was running fine earlier this spring.

I suspect a fuel pump problem with either the high pressure or low pressure pump. When the key is on I can hear a pump motor running continuously. The reservoir/separator does not fill unless you squeeze the bulb. The bulb feels normal and holds pressure.

Just prior to this occurrence I changed the fuel separator/filter. Although I've done this several times. Could I have some sort of air lock going on ?

Or, perhaps my low pressure pump is dead and the noise I hear is the high pressure pump in the VST.

If anybody has experienced anything similar it may be very helpful. I wont be able to get a mechanic in April for 4 weeks and I don't mind tinkering. I lost the low pressure pump on a Zuke once, but I don't recall hearing the other pump motor running... :hmm
 
Harpoon said:
My F250 shut down just after launching. All maintenance has been performed, two fresh tanks of fuel. Boat was running fine earlier this spring.

I suspect a fuel pump problem with either the high pressure or low pressure pump. When the key is on I can hear a pump motor running continuously. The reservoir/separator does not fill unless you squeeze the bulb. The bulb feels normal and holds pressure.

Just prior to this occurrence I changed the fuel separator/filter. Although I've done this several times. Could I have some sort of air lock going on ?

Or, perhaps my low pressure pump is dead and the noise I hear is the high pressure pump in the VST.

If anybody has experienced anything similar it may be very helpful. I wont be able to get a mechanic in April for 4 weeks and I don't mind tinkering. I lost the low pressure pump on a Zuke once, but I don't recall hearing the other pump motor running... :hmm
Click to expand...

Probably an air leak or air lock. Check the water separator for a bad seal . You may need prefil it with gas but The primer should be able to pull gas though unless the bulb is weak. You might have weak/bad lp pumps but since it ran last season, it is most likely something you did. By the way, air leaks on the on-board fuel filter are common. That clear shell often doesn't seat correctly so if you touched it, check that too. If it is completel full or completely empty y that can indicate an air leak.
Let us know what you find.
Don't run the high pressure fuel pump without fuel in it. It doesn't like to be run dry.
 
Hmmmm. I checked for leaks on all of that stuff. 10 micron separator and the plastic onboard filter. The bulb stays hard. I'm leaning toward a clog in the vst vent or the LP pump shit the bed. Understood on the high pressure... thanks.
 
Does the fuel/water separator CONTINUALLY need to be filled? Once it fills once (it's not clear from your post), it shouldn't have to be filled again... maybe after a long time of just sitting, but it doesn't sound like that's the reason here. Since you said the pump continues to run, I would start by looking for a restriction between the tank and filter (assuming you've 100% eliminated any leaks upstream of the filter). This could be a failing (internally) fuel line, clogged pickup tube, or even as simple as a clogged fuel vent.
 
Re: Yamaha F250 dead - NOT Fuel Pumps

OK, so its not my fuel pumps (either) that are making the noise. VST is full, so is filter in front. Noise is coming from throttle body see picture below. It looks more expensive.
 

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  • throttle body.jpg
    throttle body.jpg
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All fixed. Float in VST tank was preventing pump from running.
 
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