Prop Choices for 6hp pushing 3350lbs

[scot.mcpherson]

Hi,
I have a SeaSprite 23 sailboat, it dispaces 3350lbs at the water line. It was designed to hang a small outboard motor on the back. I have a 1963 Johnson Fisherman 6hp hanging on the back which pushes the boat along ok, but the propeller is a weedless 2 blade prop designed to push small fishing boats through the weeds.

I'd like to know what you think would be the best choice of new propeller for this engine to push this boat up to its rated hull speed, which is 5kts cruising and 5.4kts max hull speed. I am not trying to push the limits of making a displacement hull go faster than it's hull speed, but at present the engine pushes the hull at around 3.5-4kts, and and I wouldn't mind getting up to 5 kts.

Also since it's a weedless design, putting the motor in reverse yield abysmal results. Is just can't grab enough water to do anything worth while.

Do you folks have any recommendations for prop choice for my engine for the boat I have?

I was thinking of getting a 3 blade with reduced pitch, but not sure what the best choices in that realm are.

Thanks,
Scot

 

[Bondo]

I was thinking of getting a 3 blade with reduced pitch, but not sure what the best choices in that realm are.

Ayuh,.... Welcome Aboard,..... Donno what's available for that motor,.... but I'm thinkin' 3 Big blades,... Bigger the Better,....

Other's will be along that'll know,.....

 

[Sea Rider]

Is that engine model a through hub exhaust or a non through hub exhaust ? Assume through hub props are easier to find in different sizes.

Happy Boating

 

[steelespike]

What size prop is on it now?I assume non thru hub.
Prop numbers should be near the base of the blades.
A 3 or 4 blade should work great.But may be hard to find.

 

[scot.mcpherson]

Based on researching the intertubes I think it's a 8 x 7.25 weedless 2-blade. I haven't checked the prop for the dimensions, it is hanging off the back of the boat which is anchored out. I'll check tomorrow. It is definitely not s thru hub exhaust.

To be honest this is the first outboard I have owned so I am really learning from scratch. When I felt around the prop last night it felt like there was room for an extra 1/4 or 1/2 inch of diameter (yes I know the diff between radius and diameter) but I don't know if it's a good idea to fill that space with prop or not.

Being new to outboards I really don't know the best places to find unusual props. Doesn't seem like there are many choices available to low hp motors.

 

[steelespike]

After a brief search I don't believe the 6 hp appeared until 1965.You may find a model number on the
mount bracket. There are 3 blade props listed here for 66 and up, 8 1/4 X 7" 3 bld. Quick silver QA3178R.
Don't know if the 7" is suited for your application but it surely will provide more push.
Reverse should be better but don't expect perfection.Stoping 3300lbs is a tough assignment.
I don't know if the 65 6 hp is lost in limbo somewhere.

 

[scot.mcpherson]

So I looked on the propeller, the dimensions are not printed or stamped on it. I have pulled the motor and it's home hanging on a saw horse. I guess really my question at this point is, how do I find unusual propellers. It seems to me that if I search propellers for this motor I really only get one result along with two others that "may" be compatible, but may not be either.

Are there resources where I can look for unusual props? I mean the ones that are not just readily available. Are there suppliers of unusual props out there that people already know about?

Thank you,
Scot

 

[Bondo]

So I looked on the propeller, the dimensions are not printed or stamped on it.

Ayuh,..... Have ya pulled the prop off the motor,..??

Post up some pictures of it from both sides, 'n of the propshaft, 'n hardware,....

 

[steelespike]

Look up Propco they list 8 X 6.5 3 blade Heavy load for a 6 hp.

 

[scot.mcpherson]

steelspike, thanks

I'll take some pics tonight if I can...depends on weather.

Cheers,
Scot

 

[steelespike]

Did you get a prop from propco ? How did it test out?

 

[Frank Acampora]

I think that with only 6 hp pushing a hull that size you are doing very well at 3.5-4 kts. I don't think the engine has the power to get up to hull speed. A different prop may yield better reverse results but I doubt you will get much better forward performance.

 

[steelespike]

The 3 blade probably has twice the blade area. Increasing 1kt seems reasonable.as long as the 6 can spin it up good.
Seems likely it will do well dealing with wind and current.