boat speed?

[betayv]

hi there 1979 22 feet cruiser barnegat with a 305/228 alpha one drive I just bought a new prop is a 4 blade 14inch 21 pitch,, my boat weight is 4000 pounds+70 gallon tank, three people on board about 700 pounds, my speed is 35 mph at 4000 rpm, is that correct is the average speed thanks.

 

[Bondo]

Re: boat speed?

Ayuh,... Wrong Forum,... You want Props, or maybe General Boating....

 

[steelespike]

Re: boat speed?

What was the old prop?How did it do?Are both props aluminum?Is speed by gps?How is the hole shot?
Not an expert but I believe that motor should max out about 4,400 to 4,600.
Max rating usually appears on a label on the motor.
If that is your typical load I think you should be closer to the max rpm.

 

[betayv]

Re: boat speed?

old prop was a 3 blade 14inch 21 the speed use to be 29mph max, we cjecking the speed with gps, and yes the max rpm for the engine is 4300 but I dont like to go over 4000.

 

[steelespike]

Re: boat speed?

I agree running at max rpm is hard on the typical I/O motor but
the motor should be propped to run at its max rpm with your typical load.
Otherwise it will be struggling through the whole rpm band.Just throttle back
to attain your 4,000.You could have a good prop shop take out a little pitch or remove a little cup to gain some rpm.
Ideal cruising speed can be anywhere from just on plane to about 2,000 rpm above;depending of course on the rpm at just on plane.Experimentation or a flow meter is the only way to find the best cruising speed.