2 to 3 blade prop

[mike gra]

Hi, I have a 1966 6 hp evinrude motor on a 11 ft Achilles raft and it doesn't get the raft to plane out. The motor is in great shape and has a 2 blade prop. My question is if I change to a 3 blade prop will it a give a little bit more power to get the raft on plane? I can only find info on 3 to 4 blade props which doesn't help me thanks

 

[Sea Rider]

A 11 ft inflatable with a 6 HP OB usually has very poor performance, due to its short size there's to much hull drag to overcome fast while powered with a under powered OB, worse if with poor inflation and being a heavy boater.. Which type of floor is it, air deck, wooden, alum ? Which 3 blade pitch props are available ?

Happy Boating

 

[mike gra]

A 11 ft inflatable with a 6 HP OB usually has very poor performance, due to its short size there's to much hull drag to overcome fast while powered with a under powered OB, worse if with poor inflation and being a heavy boater.. Which type of floor is it, air deck, wooden, alum ? Which 3 blade pitch props are available ?

Happy Boating

Its a wood floor and its only rated for a 10 hp. I had a 15 hp on it at one time and it was scary fast but it was a freinds motor. I looked a while ago at props but I dont remember what it was. The motor was my grandfathers and its good to teach my kids with but wanted to have some fun with them too so just seeing if its worth buying a 9.9
thanks

 

[Sea Rider]

A 9.9 HP-OB will perform much better with the kids than a 6 HP, can always maximize a less pitch prop to develop full 9.9 HP out oif that OB.

Happy Boating

 

[porscheguy]

I?ve never known of anything to plane with 6hp. Prop choices will be limited on something like that. It sounds like what you need is a 9.9 motor.

 

[Texasmark]

Agree 6 won't do much. Been there done that. Engine is too small for tachs (maybe an after market "Tiny Tach") and a tach is what you need for meaningful info to determine where to go from where you are....which isn't very far. Sea Rider is your best info source on boats of this size. Listen to him.

 

[Stumpalump]

Put on a three. The two was the Johnson "speed" prop. Some were plastic. A three blade aluminum prop in the lowest pitch you can buy get will be an improvement.

 

[Texasmark]

Put on a three. The two was the Johnson "speed" prop. Some were plastic. A three blade aluminum prop in the lowest pitch you can buy get will be an improvement.

Yep on the Speed Prop. My first boat was a 13' wood restoration. Saved up my money ($400) and bought a 25 hp Wizard from Western Auto which came with a 2 blade alum prop. Tried to water ski (2 skis, weighed about 170 at the time) and it was a drag..... We ski'd in Talor Lake, which drains into Clear Lake which is the site of NASA south of Houston. Water was only about 2' deep with 1' of muddy silt. No life jacket. You fall off (which was a common occurrence for me) and just stand up, sinking in the mud.

Saved up some more money and bought a Michigan Wheel Bronze 3 blade....that was my "Power Prop". Not much help obviously......had no idea as to rpms with either, nor did I know much about any of it at the time but I did think I had the advantage with 3 blades over 2 since at the time Merc products came with 2 and Johnsons and Rudes came with 3 and they could pull circles around the Mercs....course I didn't know the real reason.....cubes. Before it was all over I sold the Wizard and bought a new Rude 18 and I could ski better with it than the Merc product. I was 15 and working in dad's business when not in school, rather than playing sports.

 

[Willyclay]

I’ve never known of anything to plane with 6hp.

A Mini-Max (8ft) will if you work real hard at it. BTDT with my 1947 Wizard WD-4S and two-blade bronze prop. Texasmark's youthful adventures sounds like my experience. Hope the OP can find happiness with his inflatable. Good luck!

 

[jimmbo]

Hi, I have a 1966 6 hp evinrude motor on a 11 ft Achilles raft and it doesn't get the raft to plane out. The motor is in great shape and has a 2 blade prop. My question is if I change to a 3 blade prop will it a give a little bit more power to get the raft on plane? I can only find info on 3 to 4 blade props which doesn't help me thanks

Adding a 3rd blade will just overload the engine and will lower your speed. 6hp for what you want is marginal at best. More HP is needed