F225 fuel system issue stumps Yamaha Tech

[zenoahphobic]

Had nothing to do with fuel or air leaks. Rebuilt entire fuel system, same problem. Has to be electrical. Bad relay or something somewhere.

So if you are thinking electrical again, check the voltages around the pump connection ( right at pump), listen for cycling as you had observed in the past, particularly the differences in voltage when you think the pump is on and when it is off.

[Justmeagain]

I did not see a resolution to this problem. I am having the same.

I did much of what was suggested above and took the same actions. The HP and LP pumps are new, VST was spotless when opened. All filters were replaced except in the Injectors. I replaced the Low Pressure Pump and the one that came out was working. I used it to "Polish" 60 gallons of old fuel by drawing it through the filter in the boat. I taped into the system by disconnecting the fuel line before the primer bulb using clear hose. I was amazed at the amount of air I was drawing to the isolated LP and it was compressed before going back into the tank. The LP pump was drawing 2 gal a minute (estimate) so the tank was recycled at least 3 times. Before doing this I removed the check valve at the pick-up to a straight through fitting.
My plan now is to set up the polisher and use a wet cloth on every fitting and see if it changes the air bubbles. May take a day or so, heat and thunderstorms are slowing this old guy down.

[Doggydog]

Battling a similar issue - but I only stall at idle or idle speeds. Will be curious if you find a resolution. I originally thought vapor lock or something of the sort - but my VST is now vented to atmosphere and the issue persists. I have not gotten access to an external tank yet. I will try to get that and also do a deeper inspection on the plastic pipe joints.

It does seem odd to me to think if this is an air leak - why would my boat runs fine at speed but stalls at idle? I would think the higher the RPM the more air is coming in?

Everything boils down to my VST emptying out at idle. ... Ugh.

[99yam40]

old thread,
but at idle the low pump does not run all of the time.
above some RPM is does
that is one reason sucking air will cause this problem at idle

[golfomex]

Why visiting my brother in Mexico, last week after a couple of hours of *****ing our 2014, 250hp 4 stroke engine quit and would not start. I disconnected the water separator and connected it directly to the fuel tank. The primer bulb was empty, primed it but the engine would not start. We checked the LP pump and it seems to be pumping correctly, did not check to see if we had any air in the lines. Kind of hard to do when your battling 4-foot waves. Luckily we were rescued, but the engine will not start. We checked the drain plug on the VST but to my surprise the VST had fuel. Any ideas, any help will be appreciated. I have since returned to Florida but I would love to resolve the problem.