Yamaha 70A 2500 max rpm under load.

[nikolijc]

I have a 70A Yamaha outboard motor. Here is the symptoms I am experiencing.
I can run the boat at 4000 ~ 5000 rpm for 10 to 15 minutes after that the motor looses power and backs down to 2500 rpm. There is no audible or visual indication from the panel or the motor. If I turn the motor off for 10~15 minutes or rev the engine in neutral for 5 min at 3000 rpm, the problem goes away for the next 10 to 15 min. I have changed the fuel filter and I had the carbs rebuilt last year. Any ideas?

 

[Ray Neudecker]

Re: Yamaha 70A 2500 max rpm under load.

Normally, a fuel restriction would be the first suspect. On that model, I would also check fire when the problem occurs.
Cleaning carbs is like washing your truck, works great until it gets dirty again.

 

[nikolijc]

Re: Yamaha 70A 2500 max rpm under load.

Ray,
Thanks for the info. Is one of the symptoms of a fuel restriction that the fuel line bulb being soft? I am able to sweeze the bulb flat when the motor is running.

Thanks for all of your help
~Nick

 

[Ray Neudecker]

Re: Yamaha 70A 2500 max rpm under load.

Defintely a sign of a restriction. Need to go through the system from fuel tank to carbs to correct. The problem will blow your powerhead if you don't correct the problem.