change from 2 blade to 3 blade?

[jaserin2000]

i have a 1967 johnson 6hp - model cd-24s - can i replace my 2 blade prop with a 3 blade prop? I mistakenly bought a 3 blade prop, and while I can take it back, I was wondering if anyone knew if I could use it anyway.

 

[F_R]

Re: change from 2 blade to 3 blade?

Don't know. What is the diameter and pitch? And boat?

 

[steelespike]

Re: change from 2 blade to 3 blade?

It appears all the props for 66-79 motors are 3 blade here at iboats.
get us the diameter and pitch if its intended for your motor and right for the application it will work.Original prop was 8 X 71/4. 2 blade newer models were 8 X 7 3 blade

 

[jaserin2000]

Re: change from 2 blade to 3 blade?

the new 3 blade prop is 8 1/4 x 7 1/4 and is listed for use for 1966-1979 johnson 6 hp motors - the boat i am pushing is a 14 ft solid glass River Rat.

 

[jay_merrill]

Re: change from 2 blade to 3 blade?

I'm not familiar with a River Rat boat, but if its on the heavier side for a 14' boat, and your two blade prop is the same pitch as the three blade, you'll probably like the two blade better.

I use a 1969 Johnson 6hp as a kicker on my 17.5 foot trihull. I bought a three blade prop a couple of months ago, thinking that it wouldn't be much different than my two blade, because the pitch is the same. I don't have a tach on the motor, so I can only judge by ear and speed, but I noticed a significant difference between the two - the three blade does not wind up nearly as much and my boat is about 1 mph (GPS) slower with it. Given that I only get about 5 mph with the two blade, that's a significant difference.

Obviously, your boat is much lighter than mine, but it seems like a 14' fiberglass boat is alot of boat for a 6hp motor. That being the case, the three blade may be too much prop for it.

When in doubt, however, try it!

 

[steelespike]

Re: change from 2 blade to 3 blade?

the new 3 blade prop is 8 1/4 x 7 1/4 and is listed for use for 1966-1979 johnson 6 hp motors - the boat i am pushing is a 14 ft solid glass River Rat.

It appears the 7 1/4" is the standard size prop with a 7 and 6 1/2 for heavier loads.What type load do you carry?There are higher pitch as well but probably not meant for your boat.What style bottom is the boat a rounded bildge will be harder to get up on the water a flater bottom will get up easier.
Jay with your 6 on a 17ft you would most likely need the 6.5 in pitch.
My guess is if the 2 is truley the same pitch it probably is slipping(not venting) enough to let the motor wind up a little.