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74 johnson 4hp

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Ajmrozin

New member
I bought this motor for my duck canoe, ran good when I bought but didn’t run it long. Just a couple minutes. The motor starts easy and runs well at low to mid throttle. When I run at more than mid throttle I get air bubbles in the fuel line then stalls out. The tank and fuel line are older too but when you pump the bulb it stays firm. Fresh 100% gas and oil. Before I start randomly buying parts dies anyone have some troubleshooting pointers to narrow down the problem?

Thanks
 
I put a new tank and hose on. The motor no longer stalls out at full throttle but there is still air bubbles in the fuel line between the fuel pump and the carb. Is this normal or should it be solid fuel? What would I change next? Fuel pump? Gasket between fuel pump and motor?
 
Air bubbles or fuel vapor bubbles ?----Gasket between pump and motor has nothing to do with bubbles in fuel line !----If motor runs properly why do you feel you need further investigation ?
 
I am unsure if it is air or fuel vapor. the fuel in the line is very turbulent when running at WOT. Working on boat motors is not something I normally do and I am not very experienced with engine repair in general. I just am making sure that this is normal or if it requires further maintenance before putting myself in a situation where it could be problematic. Normally when I go duck hunting it is poor weather and in the dark. Just trying to make sure a 30 minute boat ride does turn into a 2 hour paddle.
 
Check / replace o-rings in hose connecter fittings.----Check pick up tube inside the fuel tank.----If a steel 6 gallon OMC tank replace o-rings on the fuel out and vent valves.
 
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