Honda 30 HP prop

[Bill C.]

Just got a new jon boat and 30 HP Honda outboard. Dealer put a 10 x 11 SS prop on it and said that was the "middle" prop for this motor. The boat has great hole shot but I'd like a little more top end speed and lower RPM at cruising speed. At about 80% throttle and maybe 4500-5000 RPM (a guess) that boats probably about 20-22 MPH (I forgot to take my GPS today).

The standard aluminum prop supplied by Honda on this boat is 9.25 x 12. Could someone give me an idea how differently a 10 x 12 or 10 x 13 prop would behave on my boat?

The boat is an 18' x 48" bottom width, boat weighs about 330 lbs, 160 lb outboard, and people/gear was about 275 lbs today including gas. The hole shot was outstanding -- the boat jumped onto plane quickly and the bow hardly rose at all. I could sacrifice a little hole shot for some top end speed and/or lower RPM at cruising speed.

Thanks.

Bill

 

[DJ]

Re: Honda 30 HP prop

As a general rule, one inch in pitch equates to about 200 RPM, up or down, in relation.

As an example, a 12" pitch may turn 5000. A 13" pitch would probably turn 4800.

Keeping the engine RPM in its recommended band is most important.

 

[Bill C.]

Re: Honda 30 HP prop

Thanks. Took the boat out again yesterday with my GPS. Speed was 28 at WOT (I put 125 lb. of gear in the boat to simulate a typical load). It cruised at 23 at a reduced throttle that is maybe approx. 5000 rpm. As I said in the earlier post the boat just jumps on plane with the bow hardly rising at all. Based on your rule of thumbs above and from playing with the prop calculator it seems that I'd get maybe 2 MPH increase in speed, 200 rpm drop, and a little deterioration in hole shot. That would be a good enough trade off for me to ask the dealer to get me a 10x12 prop to try. Is the above about what I could expect to see?

How can I tell what props Honda recommends for this 30 HP? When I go to the prop vendors sites I see props for 25 to 30 HP outboards that range from 11 to 13 pitch to 10 to 15 pitch. That makes it seem that a 12 pitch propeller is still on the lower side and should not lug the engine.

Thanks.