Prop testing

[BigNiner19]

Did some prop testing this week. Boat is a 231 Mako and engine is a 2005 Honda BF 225 Had the engine mounted in 3rd hole from the top and had a 19 pitch 3 blade stainless prop that came with the motor.

Barely spun 5100 RPMs at WOT fully trimmed out in calm conditions but did reach 46.6 MPH.

Switched prop to Mercury Rev 4 stainless 4 blade 17 pitch and spun 5400-5500 WOT and 43.3 MPH and noticed better bow down action, boat control, cruise speed was 28-29 mph at 3850-4000 RPMS

Moved engine up one hole and ran same prop in similar conditions (not quite as calm also added 20 gals of fuel) and spun 5600-5650 WOT AT 44.8 MPH

This boat does not have trim tabs yet. What do ya'll think about where I'm at?

boat handling seems great with the 4 blade - i have a feeling with trim tabs, the setup might be right there.

 

[chawk_man]

The trim tabs really help with planing out the boat and compensating for unequal loads, BUT they actually will decrease WOT rpm's because they are adding drag - not much, but enough to be noticeable on most boats in the 20 - 30' class.

The 5600 rpm's are acceptable, but I like to get up closer to the 6000 WOT mark - it's better for the motor IMO. Once you install the trim tabs, you might want to drop down the prop diameter or pitch a bit to see if that is even better. Note that the 225 has a RPM limiter that kicks in at somewhere between 6100 and 6200 rpm.