Rodbolt 17 please help!!

[rodbolt17]

you must understand why the anti siphon valve is there in the FIRST place.
there is some good reading avalible on various USCG and ABYC websites on anti siphon valves and when they are or are not required.
and it explains why they make NUMEROUS valve break pressures.

[dorado42]

Ok..new fuel lines, new hose clamps, new racor filter and bracket, new primer ball...SAME PROBLEM...rodbolt17 had suggested a one way valve that has a 10 psi rating...is there anyway to test the valve or do I need to replace it...when it is bad does it make act like a fuel problem....i checked vacum and it is 3-4 inches of mercury...thanks again for your feedback

[FabricGATOR]

Shouldn't you be able to ascertain what the break value of the antisiphon valve by connecting it to your rig direct?

[rodbolt17]

do some reading on the USCG and the ABYC websites about anti-siphon requirements.
some hulls have them and don't even need them.

[dorado42]

I have determined that the anti-siphon valves are NOT my problem. I know you mentioned a relief valve assembly that has a 10 psi rating near the low pressure fuel pump. Can you explain how I would be able to test the valve to see if it bad? If it is bad does it seem to be a reason for the boat problems I am experiencing. Everything is new to include, fuel line, hose clamps, racor filter, racor housing, fuel bulbs and also ran one motor with new anti-siphon and one without an anti-siphon valve, but both experienced the same problem. Can the relief valve assembly be "cleaned" or just replaced? Thanks again!

[rodbolt17]

apply pressure to the inlet side, it should break at about 10 PSI and then hold it.
no repairing that valve and Yamaha is quite proud of it.
typical symptom of that valve failing is erratic/stalling below about 1200 RPM.

[Bilge Rat]

Both motors have the same problem?

How are your fuel bulbs oriented? Are the motor ends of the bulbs pointed down instead of level or up?
This is a long shot but on one boat with a brand X bulb it made a difference.

Does these motors use a carbon filter to vent air out of the VST and are all hoses clear?

[dorado42]

Both motors have the same problem...the port motor is more frequent than starboard...but acts the same, when it acts up. I know when the port motor (the one that acts up 80% of the time) fails I have to pump the ball 8-10 times to get the primer ball to get hard, where as the starboard motor only takes about 3-4 pumps to get primer ball hard. It seems like the VST tank is running out of fuel when I take off and once I either pump the ball before it dies or pump the ball after it stalls then it runs fine. I know it sounds like a fuel pump but I just put new low pressure pumps on it.

[dorado42]

so RODBOLT17 what do you think would cause the VST to run out of fuel when I take off after sitting for an extended period of time. If I sit for 10-15 minutes it is fine....it seems to be only after 20-30 minutes it has a problem. I know you said the fuel relief valve assembly is ususally an erratic/stalling below 1200 rpm. Is ther any other way the VST tank will run out of fuel, I did have a fuel pressure gauge on schader valve on VST and it maintains 40 psi. Any suggestions is GREATLY appreciated.

[dorado42]

Was working on boat today and a chunk of cable sheathing missing on negative cable going from battery switch to engine...it was deep enough the wires were exposed...will further inspect tomorrow...but is it possible that problem i am having is electrical related not fuel related

[madharchod]

agree to disagree is the name ,with these engines there are two pumps one a low pressure and the other is a high pressure which is from the VST ,now if your engine is not idling its most probable the low pressure pump which is located in front of the engine near the spark plug and why you getting the full WOT run in the first place is because Your VST is full and the pressure is correct to give the engine the supply it needs and when you stop the low pressure pump aint good enough to fill the VST hence you get problems ,so the bottom line is check the pumps as some times the diaphragm of this low pressure pump have a minor crack which causes this problem which you are facing they only 39.00 part from boat net shop and you can easily install it yourself
cheers

[dorado42]

The motors will idle....and run WOT....i have already replaced the low pressure pumps....problem occurs after drifting while fishing for 20-30 minutes and then bogs down when accelerating...

[mitch]

low pressure fuel pump

madchord you still at it fool it is a f225 it has a electric low pressure pump you are just spreading disinformation that is OF no frigging use.......... ramblings of a fool.

[99yam40]

I did have a fuel pressure gauge on schader valve on VST and it maintains 40 psi.

Was that pressure maintained while problem happened?

[mitch]

Was the 40 psi under load or was it with key on motor not running