Motor Losing Prime

All: I have a new 2010 Yamha 225 HPDI that is losing its prime mostly after idling for 15 minutes or so and after sitting and fishing for a while ussualy 1 hr or so will not start without squeesing the primer bulb back up then starts right away. Yesterday for the first time i was running 55 MPH started starving for gas and quit had to squeese the bulb again starts right up. Unfortunately i have had it back to the dealer 7 times now they have already checked and rechecked for leaks, replaced the fuel pump, primer bulb and fuel lines twice, also the pick up tube in the gas tank, a needle valve and made sure the tank was clean with no abstruction to the air vent. Any feed back you all may have would be greatly appriciated loosing my patience.

Falcon

Is the primer bulb mounted with vertical orientation and arrow up? Is the antisyphon valve still in your fuel tank? It is recommended. Are the lift pump diaphragms ok?

Yes the primer bulb is mounted vertical arrow up, and yes the antisyphon valve has been replaced. Do not know on the lift pump diaphragms.

Thanks
Falcon

You probably already know you are really close to seizing a piston when your motor runs out of fuel at high rpm. Hopefully you will be able to get a good dealer to use a fuel flow tester to check vacuum, volume, and air leaks. This can all be done in the shop with that tool.
I really think it is also worth looking at the lift pumps. When the motor is idling and you pump the primer firmly a bad pump diaphragm will cause the motor to load up and loose rpm.

what does it matter if the primer bulb is mounted vertical? Mine lays horizontal and it doesnt lose prime. 2004 150 hpdi

It does not matter where it lays. It matters if the arrow is pointing in the right direction. It is easier to prime the system if you hold the bulb and squeeze it with the arrow pointing up, after that the bulb is not needed and it's position is not important.

Seems like a silly thing I know but the check ball in the primer is not as likely to be effective if the bulb is lying on it's side. Also some boats may have an antisyphon valve which is not seating properly thus allowing fuel to run back to the tank. Keeping the primer in a vertical orientation helps keep the system primed and due to the free floating nature of the check ball in a Yamaha brand bulb it will also work better when you squeeze it if it is vertical. Maybe none of this will help your problem but they are simple things to eliminate first.

Welcome to my world. I have 9.9 kicker next to my 150. My kicker loses prime. But not at regular time intervals. I had a full tune up on both in the spring. Took it back after trolling and mechanic set the idle up. Went back out. A little better. Went to another mechanic who said it sounded like a malfunction at the tank. The dip tube into the tank has a screen in it. He said to clean it. On the outlet side of that, there is an in line check valve. He said it may be gummed up or a foreign particle is under the ball. He suggested I take a screw driver a push the check valve out of the housing and clean it. Push fron the outlet side. I have not done this yet, too busy. Let me know if this helps and I'll do the same. Matt [email protected]