New Member Needs Help! 150 hp Vmax

[Lobo48jim]

Got a 2001 150hp V max Yamaha with a problem at high speed.
Motor runs fine at 3000 to 3500 rpm but when I open up throttle all the way jumps to 5000 rpm and runs fine for about 10 seconds and cuts back to 3000 to 3500 will run fine again, if I wait about 2 to 3 mins. At that speed I can go to full throttle again will cut back after about 10 seconds. I have a fuel separator that hasn't been changed in 6 months going to change it. If problem is still there can anyone give me and idea on what to check. THANKS JIM FOWLER

[99yam40]

monitor fuel pressures to see what is going on when problem show up

[Lobo48jim]

No gauges

No way to monitor fuel flow it is a 13 year old outboard on a 21ft bay boat but thanks for trying to help. LoboJim

[Lobo48jim]

Could it be

The high speed jets in the carbs are the fuel pump? Thanks for any help, I am retired and they get $120 an hour for labor so I will have to wait for a couple of SS checks to come in to afford it. Guess I will fish from the bank! Any ideas greatly appreciated. LoboJim

[99yam40]

you can hook up a fuel pressure/ vacuum gauge between the fuel pump and the carbs with a tee to see what the pressure is doing.
Vacuum can be checked between the fuel pump and the tank at different places to help locate restrictions.

jets are not fuel pumps

when was the last time you replaced the fuel pumps?

are you sure the tank vent is open allowing tank to not form a vacuum

[Dennisg]

HI, I have had a very similar problem. It turned out to be the screen, at the end of the fuel pick-up tube in the fuel tank. It seems to get coated with a kind of slime and other bits and pieces on debris. In my case, I removed it, I felt it was totally not necessary because I had the Yamaha 10 micron fuel filter, water separator up stream between the tank and the motors. After I did this I never had another fuel problem, I had the boat for many years after this repair.
Good luck, Dennis please let me know if this helped. Sometimes it's the simple, not so obvious, things that are overlooked. The above has happened to a surprising number of friends.