Reply To: Newer Yamaha 50 HP 4-stroke question

[David Stanton]

Thanks for the tank reminder. His fuel tank is factory built-in under the floor of his 16′ Lund fishing boat so no chance of the fuel line being reversed, but, good idea – I could take the tank from my 25 HP Yamaha 4-stroke on my pontoon and try it. He hasn’t mentioned stalling at low speeds. He does have a lake one mile from his house, so we could drop it in so I can see how it runs at high throttle if I can’t figure it out in his driveway. He uses 10% ethanol gas due to limited availability of ethanol-free where he lives, so that could have created a problem over its 16 years..

I once cobbled in my Yamaha tank to the MerCruiser inboad/outbaord engine in my ski boat when it would bog at sustained high speeds, and it ran fine on the Yamaha tank. I found the anti-syphon check valve was bad with it’s spring broken and jammed up. A couple weeks later, same symptom, and ran on the temporary tank OK. This time it was the pickup screen in the built-in tank clogged with crud that somehow got in there.
Dave