Possible Ventilation?

[mg_dragon]

My father-in-law recently puchased a 1966 model 200 Mercury. I inherited the task of getting this motor in to shape. I have changed the impeller, cleaned the carb, and have the motor running pretty smooth. The problem I now have is that when I take off from a stop the boat is slow to accellerate and the engine rpms are high but eventually it planes out. I have tried all the trim settings and the problem is the same on all. The boat is a 14' aluminum v-hull. The only thing missing from the motor is the anode plate from above the prop. Could this be the cause of this problem or could ther be another prblem?

 

[Dunaruna]

Re: Possible Ventilation?

[colour=blue]Do you have a tachometer fitted? Where is the AV plate in relation to the bottom of the hull?

 

[WillyBWright]

Re: Possible Ventilation?

It sounds like you have a spun hub in the prop. That's the rubber cushion between the sleeve that fits the propshaft and the prop. Check around for a used one. New ones are still available. Only a prop from a 200 will fit.

 

[mg_dragon]

Re: Possible Ventilation?

The anti-ventilation plate is just below the bottom of the hull. The prop doesn't act like the spun hubs that I have had in the past where the boat would slow down while accellerating. This boat continues to accellerate and planes out. With the anode plate missing this causes a cup above the prop. There is a hole in this cup where I am wondering if exhaust could be coming out of. I am thinking of fabricating an aluminum plate to cover this area due to this motor running in only fresh water. Does anyone know if this would cause a problems or maybe cure this one.

 

[WillyBWright]

Re: Possible Ventilation?

Might be a cure. Maybe it's sucking air or exhaust into the prop, but I'd think that once the boat was in motion, that source would be too far back to affect the prop. Are you sure it's running on both cylinders? 2-stroke twins run much smoother with just one cylinder firing, but certainly lack power.

 

[mg_dragon]

Re: Possible Ventilation?

I getting spark at both plugs. There appears to be plenty of power from the motor. The exhaust bubbles travel about 20 feet behind the boat when accellerating. I will try to get the plate put on this week and let you know the outcome.