1987 Mercury Mariner 45hp - problems running fast

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I have an 87 Mercury Mariner with 45hp that doesn't seem to be getting enough gas. It will run normal at full throttle for 1-5 miles and then suddenly slow down to about quarter throttle speed while still being in full throttle.<br /><br />Everything in it has been replaced or rebuilt, but the problem persists. After the ball is pumped a few times it will take off, but then slow down quickly.<br /><br />A pro has looked at it and replaced the electric box, but it still has problems. (Only in the water. It'll run all day dry)<br /><br />I think it may be something is overheating or some kind of sensor is messed up. Does anyone have any idea what I could do?

 

[Yepblaze]

Re: 1987 Mercury Mariner 45hp - problems running fast

Try a back up hose and tank assy just to eliminate that. <br /><br />Then rebuild the fuel pump (again if required) with the check valve assys, if applicable.