26M + Honda BFP60 Performance

[ChuckieTodd]

I raised the mast yesterday for the first time since Hurricane Isaac. I figured I'd do some testing with my new 14x9 prop and report the results. Ballast tank full. Boat was loaded with my 170lbs, maybe 300lbs of gear, and 6 gal of fuel. Wind was out of the north at 10mph. Light chop. First run was SW (215 deg) out of Ocean Springs harbor. Max speed was 15.2kts at about 5100 RPM.



Last week I made a run with the mast down and was getting about 16kts so the rig appears to be adding significant drag.

Second run was NE (35 deg) back into the harbor. Max speed was 14.5kts. As you can see on the Garmin, I'm down to 5.1gal by now.



I'm very pleased with my decision to switch from the 14x11 to the 14x9. Not only can I get above 5000k rpm, there's less prop walk and docking is much easier.

[Whipsyjac]

Great info! Especially since like half the forum members I'm trying to figure out which prop to buy.

I ran some of your RPM vs Speed numbers through the formula given on another thread and the Pitch RPM Speed formula is bang on. Thanks for a real world example to test the theoretical math against.

Your pitch 9 X your rpm 5100 = 45,900 inches per minute

divide by 12 inches per foot = 3,825 feet per minute

multiply by 60 minutes per hour = 229,500 feet per hour

divide by 5,280 feet per mile = 43.4659 miles per hour

multiply by 0.8(20percent slip) = 34.77 miles per hour

divide by 2(or your specific gear ratio, Honda BF is 2.03:1 IIRC) = 17.386MPH

divide by 1.1507miles per knot = 15.1kts

Not my formula, I found it on another thread on this forum. I would also like to see at least 3 real life examples match the formula before I bet on it. It was just cool to see an example that worked out, and confirms for me at least that I should be looking for a 9" pitch.

Willy

[raycarlson]

why waste all that new expensive horsepower pushing a full ballast tank, ballast is for sailing, you don't need it to motor unless your in heavy heavy seas.

[ChuckieTodd]

why waste all that new expensive horsepower pushing a full ballast tank, ballast is for sailing, you don't need it to motor unless your in heavy heavy seas.

You're probably right but I'm still a little nervous on the boat without ballast. It just doesn't feel right.

[Tomfoolery]

Being that the rated speed is 5000-6000 rpm, with rated power at 5500 rpm, I'd guess that if you drained that ballast, you'd get pretty close to the sweet spot. If you were going to always run with ballast in, then I'd have a shop take 1/2" to 1" of pitch out of that prop to bring the engine speed up a little more. But that's just me.

[Seapup]

Those numbers look great to me for a full ballast M. I would be interested to see what it does empty ballast, bet you would be knocking on 20mph. Shows that the low gear ratio/large prop are key factors in moving our barges.

You have the "power thrust" 60 with the 2.33 gear ratio right?

[Divecoz]

For me and YMMV Unless I am actually in need to run fast.. She rides at most speeds in most weather , better with a full ballast.. True I have run her with ballast empty just for the fun of it.. But most often she has a full ballast..

why waste all that new expensive horsepower pushing a full ballast tank, ballast is for sailing, you don't need it to motor unless your in heavy heavy seas.