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Changing from a 3 blade prop to 4 blade

R

RKMcP

New member
I have a Maritime Skiff 16 (1994) with a new Honda BF60A motor. With the prop that the dealer installed (Honda 11x15) I am able to reach 33 mph at 5800 rpm. I would like to try a 4 blade prop, but have no idea what diameter/pitch to try. Honda has a number of 4 blade prop that they list as being appropriate for the BF60A, but my guess is that using one of theirs I'd be selecting a 10.5 inch diameter 12, 13, or 14 pitch. Does anyone have any advice on what I should be looking for? Thanks.
 
There is seldom a definitive answer on prop diameter and pitch that gives the optimum efficiency. Normally, optimum hole shot is not compatible with optimum cruising efficiency. You can only experiment and be satisfied with what works for your particular boat. If you have a Honda shop nearby, then they will often have spare props laying around which some will allow you to use to experiment.

Given that you are attaining acceptable WOT with your current prop, I suspect that you don't want to change the diameter and pitch of a new 4 blade by very much, say a 10.5 X 15 or an 11 X 14. Whatever you end up with, make sure the your WOT is within spec. For that engine, I think it should be 6000 rpm +/- 200.
 
Spoke to a couple people the recommended a 4 blade prop to me. Honda 200 on my rig. All stated it would have a better hole shot but less top end. Would plane at a lower speed.
 
I think the idea was that by having the hull up on plane at a lower speed you gain efficiency? Never felt the need to try.
 
WOT rpm for your motor is 5000-6000 rpm so your already over propped. MPH is what it is rule of thumb is 200 rpm per inch of prop your overall performance would improve with about three inches less pitch with the 11 inch prop 11 x 12 should bring you around 5500 wot rpm. For fuel effeciency run it around 3/4 throttle it will extend service life of the engine also. Less pitch will improve the hole shot so with a 10.5x12 four blade would work well also. If you want faster get a bigger motor. Always size the prop with wide open rpm. The lower end will take care of itself.
 
My bad you said it is getting 5800 WOT rpm you can go a inch less on the pitch and gain some on the hole shot and keep the rpm around 5000 for fuel efficiency.
 
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