bf9.9d3 prop advice on gheenoe

[73 Dolphin]

Just picked up a honda 9.9 2003 short shaft with the power thrust 4 blade 9 1/4 dia 9" pitch prop. I understand this motor is more of a kicker than my 1982 9.9 evinrude. The evinrude really pushes this 120lb boat so much quicker. Partly because its 20lbs lighterand partly because of the higher gear ratio than the honda. I really like the honda for all the 4 stroke reasons but want it to be less of a slug on the water.

My options on re-proping would be a 3 blade 9 1/4 with a 10" pitch or a 4 blade 9 1/4 with an 11" pitch.

Anybody have any real world experience with re-proping these power thrust hondas with 3 blade props?

Again, I'm not pushing a 27 foot sailboat. Just a 15'4"
Gheenoe weighing 120lbs. Also im not really too worried about trolling. Looking for top end speed.

Thanks!

 

[hondam]

I think switching to the standard style propeller from the big eared power thrust prop is going to make a big difference. The increased surface area of the big eared props make them a lot harder to turn and is what is causing your performance problems. Its not all about diameter and pitch you also have to account for blade geometry. I like the 4 bladed props especially for tiller engines because it makes them easier to steer. I think either one of the props you have chosen will be a big step forward but could not tell you which one would be best, test runs would be the only way to tell for sure.

The only thing that makes a honda "power thrust" engine any different then a regular honda is the prop and a sticker. Other then that they are exactly the same.

 

[73 Dolphin]

Thanks. I think the 3 blade is the way to go. I will have to try it and report back. I dont know if my search skills are lacking lately but i cant find a single thing on the web about putting a 3 blade on one of these.

 

[73 Dolphin]

Went from a 4 blade 9" pitch to a 3 blade 10" pitch ( both 9 1/4" dia )
No discernible difference.
( maybe 1mph - completely not measurable between different days - It was slower than the four blade when I took it out yesterday )
Only other option I see is an 11" pitch 4 blade.
Just dont want to spend another $80 to see if it makes a difference.
I was was really hoping that someone had found a happy medium.
Interestingly the box has bullet points for the 3 and 4 blade props printed on it.
"SPEED" is listed on the 4 blade not 3 blade description.
Maybe the 4 blades are somehow faster?

 

[hondam]

If you work with a local shop most likely they will work with you to find the right prop. They will often exchange props until you have the one that will work best.

 

[73 Dolphin]

Yes. Thanks. That is one route I can take. I think i need to hook up a tinytach ans see how many rpms Im running at WOT. Should be 6000 rpm. Perhaps the pitch is too tall. I will try to update this thread as every other I have seen on the subject is never completed. Hopefully in the end this might help some one as I cant be the only one looking to get speed from a honda 9.9 powerthrust.

 

[Sea Rider]

Without an induction tach you'll be blindly guessing. Tach both 3-4 blade props lightly loaded and check which one delivers the highest wot rpm, need a prop to rev around min 5500 or top 6000 rpm. If more prop pitches are available to play with, can maximize a prop later. Would recommend Hardline Hour/Tachs

Happy Boating

 

[73 Dolphin]

I bought a tach and a 3 blade 9.25x8 pitch prop.
Wot 5950 rpm. Top speed 15.4 mph.

5450 rpm wot for the 9.25x10. Top speed about the same.

Have not had a chance to check the 4 blade 9.25x9 yet.

 

[Sea Rider]

A 3 blade less pitch prop will gain higher wot revs while lightly loaded compared to a 10. The more wot revs gained with 8 pitch accounts for better hole shot, carry more load sacrifying minimum MPH which can live without compared to a 10. Check 4 blade wot rpm with same weight as with previous 3 blade wot runs. Will be interesting to see wot results. Installing an induction tach opens a new boating world while playing with wot RPM, loads, props to dial top water performance for any combo.

Happy Boating