Mercury 80, 1979

[bigiron]

My Merc 80 starts well and seems to run well.<br />However As I am running on the plane at about a steady 20-22 MPH suddenly the engine will lose speed and the boat will settle. If I give it more gas it will jump back up on the plane at a higher speed. If I try to run again at the 20-22 MO+PH range it will go for a while (3-5 Minutes) and then do the settling thing again. Would adding plaing fins to the motor help?

 

[WillyBWright]

Re: Mercury 80, 1979

Is there a reason that you have to run at that exact speed? Depending on the hull, that's about the speed where many boats are at a threshold between planing and not. I don't think a hydrofoil would help, but you don't know until you try. One thing to consider is that you'll be adding drag and that might be counterproductive. You might be better off with a propeller with less pitch. That would give you more RPMs which would give you more power from the motor which might help keep the boat's speed where you want it. A tachometer would be vital to prevent overrevving if you go with a small enough pitch that would allow the motor to run too fast at full throttle.

 

[bigiron]

Re: Mercury 80, 1979

Thanks WillyBWright<br />I run at 22 MPH because the lake is very rough and my tri-hull gets beat up at higher speeds. However I see that I ahve 19 in prop and I will use your suggestion and downgrad to a 17 in prop. I bet that will help