73 Johnson 6hp, 3 blade prop?

[BoatFisho]

Is there much benefit in upgrading from a 2 bade prop?

Also what specs do I need to look for when hunting a 3 blade prop for the mighty 6hp?

 

[Texasmark]

Re: 73 Johnson 6hp, 3 blade prop?

Probably not. However, the little 3 hp fisherman of the 1950's era, the one with the slanted drive shaft....to slide over weeds, did have a weedless 3 blade....but that was because the blade width was half what the regular 2 blade prop had on the horizontal shaft engine and the 3rd blade was to help make up for the loss of torque with the weedless blade geometry...half way down the prop the blades took a sharp turn to the south...meaning there was weedless operation, but not much torque...The design was for weeds to slip off the blade...as did the water needed for propulsion....my take on it.

If you are not happy with your propulsion, get something that will suit you. As stated, 6 tain't much.

Mark

 

[steelespike]

Re: 73 Johnson 6hp, 3 blade prop?

In ideal conditions a 6 will do about 14 mph.
What is it you would like to accomplish?
What is your setup and typical load?

 

[BoatFisho]

Re: 73 Johnson 6hp, 3 blade prop?

Just me and the boat and some rods. 14-15mph will do fine. Its not that I need a 3 blade, its just I know a lot of people swapped them over and I wasnt sure what the benefit was. They arent cheap anyway

 

[steelespike]

Re: 73 Johnson 6hp, 3 blade prop?

I think the 2 blade should work unless your a 300 pounder. The 2 blade will let the motor rev easier.
Original prop was a 8 X 7 1/4. The 3 blades listed here are all higher pitch which would lower rpm and slow hole shot.
A 3 bade of the proper pitch would usually do better with a heavy load than a 2 blade.
Weight placement ,motor height and trim is also critical. Sometimes a little motor will do better with a tiller extension
so you can get in the middle seat.
Tell us about your boat and how goes now.

 

[BoatFisho]

Re: 73 Johnson 6hp, 3 blade prop?

yeah plan to make a tiller extension. sometimes i have the lady with me and she sits up front, it just about planes. im 250lb, she is 60 odd. 2.9m inflatable.

 

[steelespike]

Re: 73 Johnson 6hp, 3 blade prop?

Ah,an inflatable.Light but not too good on getting up on the water.
especially when weight is added.Be sure it is fully inflated.
See if you can see how deep the motor is in the water at speed.
Maybe just reach over the back and snap a picture.
Most little motors with a 15" leg are actually about 17".It's possible you may be dragging too much motor through the water.
Probably won't gain much but could be the difference in planing and not planing.
Most little motors you can gain an inch just by putting a 1" stick on top of the transom. Just be sure the clamp has a good grip.
If the motor is really low you can build up the transom.
Play with the motor trim as well.

 

[BoatFisho]

Re: 73 Johnson 6hp, 3 blade prop?

doesnt seem to be dragging much, i thought about that too. to be honest ideally i need an 8 but the 6 is cheap and i like it and often im by myself and it does about 15mph. i was considering a perm trim tab to see if i could get it to plane a bit quicker. yeah i make sure the inflatable keel is hard, its a hard floor which helps but not as good as a rib.