Best prop for a little 12? boat, 6hp pushing 550lbs or so

[bnurczyk]

Hi all,
I won a little Lund A12 at the local boat show, hull is 160 lbs rated at 10 hp.
I picked up a 1968 Johnson 6 from a friend, it has the OEM 2 blade 8x7-1/4 prop on it now but it?s worn out. It measures out at under 7-1/2? dia.
From about half throttle to wide open there is a significant increase in RPM but not much speed gain, lots of slip and churning of water, I think I could walk faster! (no tach or speedo on this little puddle jumper).

So, a deep V front with a flat bottom in the stern, 6hp 2-stroke. With motor, gas, trolling motor, battery, two adults and gear, max weight 650 lbs.
Available props;
2 blade 8 x 7-1/4
3 balde 8-1/4 x 8
3 blade 8-1/4 x 8-1/2
Which would be best in my application? The gas motor will not be used for trolling.
Bruce

 

[steelespike]

Re: Best prop for a little 12? boat, 6hp pushing 550lbs or so

You need to evaluate your setup with just you and the boat and required safety gear.Might require a tiller extension so you can sit
in the middle seat.We can try to figure it out using just a gps for speed.
But a Tinytach would be a big help and could be used on any future motors.The motor should be able to make about 12 mph.

 

[Texasmark]

Re: Best prop for a little 12? boat, 6hp pushing 550lbs or so

Hi all,
I won a little Lund A12 at the local boat show, hull is 160 lbs rated at 10 hp.
I picked up a 1968 Johnson 6 from a friend, it has the OEM 2 blade 8x7-1/4 prop on it now but it’s worn out. It measures out at under 7-1/2” dia.
From about half throttle to wide open there is a significant increase in RPM but not much speed gain, lots of slip and churning of water, I think I could walk faster! (no tach or speedo on this little puddle jumper).

So, a deep V front with a flat bottom in the stern, 6hp 2-stroke. With motor, gas, trolling motor, battery, two adults and gear, max weight 650 lbs.
Available props;
2 blade 8 x 7-1/4
3 balde 8-1/4 x 8
3 blade 8-1/4 x 8-1/2
Which would be best in my application? The gas motor will not be used for trolling.
Bruce

Your engine probably shares lower sections with at least a 7 1/2 and props for sure, and prop may also fit a 10 hp. Nice to have some numbers, but I would be inclined to stay with what you have. You have a good sized load for that small a hp engine. I have run several boat engine combinations over the years in that hp/boat size range (5 1/2, 2ea 7 1/2, 9.9 and 2ea 10's). Even running alone the smaller engines had their work cut out for them. 2 cycle engines like to run on the high end of the power band and do not like to be lugged. I'd stay with what the previous owner wore out.....must have liked it; he wore it out.

Mark