Suggestions for Honda BF-20 prop

[VForce]

Recently installed a 2006 Honda BF-20 4 stroke onto my 15' trihull to use on a HP restricted lake.

Current prop is aluminum, 4 blade, 9-1/4X10.

Currently, my max WOT is at 4100 rpm per tiny tac. Engine is noticeably lugging, and boat will not plane. (recommended WOT is 5000 rpm min to about 5500 max)

Weight of boat, motor, equip and 4 passengers is 1500 lbs.

I do not have a speedo or GPS - but a guess is that we are presently going 15 mph at WOT.

Should I drop down to a 3 blade (will that give me some rpm back?) or keep the 4 blade due to the extreme weight of the boat/load?

Also, how low in pitch should I go? I am thinking that if I go down to a 9" dia and 7 pitch, and swap to a 3 blade, I should get back about 900 rpm, which will put me at min WOT.

Most time is spent at low speed (no towing/tubing), but I noticed this engine 'makes oil' after a while. I would like to be able to get boat up on plane (if possible) to heat up the engine oil every now and then.

Could anyone recommend some alternatives for a prop? Thanks

 

[steelespike]

Re: Suggestions for Honda BF-20 prop

That is a tough assignment for a 20 hp.And you have to get the rpm up.
It would appear youre on the right track.I think in your case getting it toplane is the best way to get the rpm up.Again a tough assignment.The experts may have some suggestions for a prop.
Careful weight distribution and motor trim is critical.Also eliminate as much weight as possible.a 3 gal plastic gas tank light weight danforth type anchor,
a styrofoam cooler kept in the shade for minimum ice melt(less ice less weight)plastic dingy oars instead of wood.If your hauling around a remote steering setup get rid of it.A few pounds could be a difference between planing and plowing.
You might try something like smart tabs to see if it will help plane.