[jbjennings]

Guys,
I have a '74 merc 3cylinder/2carb. 65hp outboard on a 24ft pontoon barge. I can't find any numbers on the outside of the prop but haven't taken it off yet. It will push the pontoon boat with 2 men aboard at 17 mph on the gps. It doesn't sound like the motor is revving up high enough to me and I don't want to lug the motor and wear it out since the old thing runs really nice. Does anyone have any suggestions on the prop size and pitch that would be best for this thing? Is this about what speed it should run? Should I see the prop size and pitch if I take it off somewhere on the inside of the prop?
thanks, Oh, and here's a pic of the barge--it's a '78 model but the pontoons don't leak. maybe a pic will give you a better idea of the weight of the boat.
thanks,
JBJ

[steelespike]

Your certainly in the ball park I would think 17 to 21 mph would be possible.
You may want to check your setup raise the motor vertically.It won't give you much at those speeds but every little bit helps especially at $4 + a gallon.Don't make any prop changes until you know your actual wot rpm.
A 1 inch change in pitch will net about 200 rpm increase pitch lowers rpm
decrease increases.There may be numbers under the prop nut or a prop shop can measure it for you.