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40 hp Johnson bogs down at full throttle

M

Moon Pie

New member
Just purchased used boat & motor. 1986 40 hp Johnson. Took it out last weekend and it started right up, idles with no problem. Got to up on plane and drove it around for about 15 minutes when it bogged down at full throttle, but ran fine at slow speed and idle. Took it home and put new fuel in it, then back on the water this weekend. Same issue, but never did get to full power. I disconnected the fuel hose while running and it took right off, running like a champ. I did this a couple of times with the same result (the fuel tank vent is wide open). The fuel tank and hose (6 gallon plastic tank)are brand new, but the fuel connector that plugs into the motor looks old. Is there any way the tank/hose/connector could be the problem? If not, does anyone have any suggestions?

Thanks.
 
a little more info - disconnect fuel line at engine or at fuel tank? is the primer bulb collapsing ? also might try running with tank cap very loose.
 
That might indicate that you have a float valve in the carburetor leaking / not closing.----Or an issue with the fuel pump.----What type of fuel pump is on it now ?---VRO or something else ?
 
Personally, I don't like most plastic portable fuel tanks. Can you get another known good fuel tank and hose to try? VRO? Yes/No?
 
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