Yamaha F50 No Power Under Load - 1080 Hours

KevinDU

I am having problems with my 2007 Yamaha F50 AGAIN! Haven't been out on the water yet this year. I experienced power loss last year and after 2 weeks at the local Yamaha dealer whose mechanic ran up 10 hours of labour and finally installed a used fuel pump, it ran again for 80 hours until I winterized the engines/boat last October. I took the boat out in May and now the same problem has returned. The engine runs and gets 6000 rpm (when on the earmuffs) but when in the water under load I get only 3000 rpm. The computer diagnostic found a faulty injector and after replacing the injector and paying another $1000 there is no difference to the engine's performance. The boat is back in the shop now. This is extremely frustrating because the mechanic doesn't seem to know what is going on here and I am spending mega-bucks and not getting any results. (Running 2x Yamaha F50s; the other engine with the same 1080 hours runs flawlessly). They are thinking of putting in a new fuel pump but it's all a guessing game.

hardee · Posted: Tue May 21, 2019 4:56 pm Post subject:

Questions:
1. Are you using 2 separate fuel tanks?
2. Are you using Marine Stable?
3. If so, any chance you doubled up in the tank for the engine that works well?

Harvey
SleepyC Moon

BrentB · Posted: Tue May 21, 2019 6:57 pm Post subject:

Is there another shop to take your boat?

jennykatz · Posted: Tue May 21, 2019 7:40 pm Post subject: Engine problems

Find another shop 10hours for diagnosing and then putting in a used fuel pump
Question the 07 Yamaha’s are fuel injected engines you said you changed an injector and that was $ 1000 wow what kind of $ do they get per hour labor Have you checked the prop for dings Is the bottom cleaned You say the other engine runs fine what rpm will the running engine be when the broken one only runs up to 3000 rpm Have you checked the spark plugs ,coils, wires
Is the primer bulb loosing its hardness so you might have fuel starvation check all fuel lines if they are old they might be collapsing under load Replace line from the gas tanks Another way get a 6 gallon fuel tank and run engine on that tank take away the fuel problem then make sure engine prop is good Good Luck Jim

starcrafttom · Posted: Tue May 21, 2019 8:13 pm Post subject:

Sounds like your prop is slipping on the hub. You will not be able to move it by hand on the hub but a under a load it will slip. This maybe a new problem from last year but with similar symptoms. Eliminate the easy to repair before chasing your tail assuming you have the same problem as last year.

tsturm · Posted: Wed May 22, 2019 2:00 am Post subject:

starcrafttom · Posted: Wed May 22, 2019 11:50 am Post subject:

Only if its completely shot. I had the same problem on the 225 it would over rev then come down but not have power. Just something to check.

fuel lines and bulb are the other thinks I would check. If you are getting air in one line the other motor will pull fuel away from the first motor. But that should be an easy check. Buy a small tank and new hose for that motor and use it to test the motor. takes 5 mins.

but the owner said that they had full rpm in natural but not when a load was applied. so the hoses and motor under use in both conditions but not the prop. If this only happens under load and the prop is the load?????

KevinDU · Posted: Wed May 22, 2019 11:54 am Post subject:

Thanks for all your comments and suggestions. I ordered a new fuel pump which will be installed sometime next week. A used fuel pump fixed the problem last year and the engine ran okay for 80 hours on that one.