'79 150HP Johnson/22' Starcraft Mariner, What Prop?

[roughshot]

Ok. After reading post after post about prop selection and all the great advice, I have come to the conclusion that no two prop selections will be the same and that I am still uneducated with respect to my prop needs.

Here is my scenario;
22' Starcraft Mariner - Stripped down for being a layout tender boat for Duck hunting.
I am replacing or removing everything from the boat including, foam, deck, console and seats.
This boat loaded with have a 3 to 4 guys, let say 1200 lbs dressed.
200 decoys - 200 lbs
Gear/Safety - 300 lbs
Layout boat - 250 lbs
Total - 2000lbs (excluding boat & Motor)
add another 2500 lbs for Motor, Fuel and Hull

I'll be running a '79 150HP V6

I don't know the RPM range.

What is my best prop selection for this Load? What about when I'm not Loaded and just out for a ride?

Thank you in advance.

 

[jdub2]

Re: '79 150HP Johnson/22' Starcraft Mariner Modified

Re: '79 150HP Johnson/22' Starcraft Mariner Modified

At 4500 pounds, I'd consider a 14" or 15" pitch. Not loaded, maybe a 17" to 19" pitch. Definitely compare/contrast these pitches after doing more homework. I would err on the conservative side (lower number pitch) with the different numbers you will be recommended.

Using boat & people weight, horsepower, gear ratio, and max rpm range, I successfully calculated the proper prop replacement for my boat, as my old prop had no number on it anywhere, possibly obscured by corrosion. With the new prop I bought and installed, I'm right in the ballpark with performance. I think it turned out to be an exact replacement, aside from brand.

 

[roughshot]

Re: '79 150HP Johnson/22' Starcraft Mariner, What Prop?

Thank you.
With the calc I've done and searched. The prop recommended was a 15 x 17 3 Blade.
As I will be pushing a heavy load and maybe in some large chop of 3' to 4'. Would a 4 blade prop better suit me for more pushing power? I'm less concerned with my top speed and more concerned with being able to get on plane and stay on plane at lower speeds. With some of the distances I may be traveling. Fuel efficency is a desire.

 

[steelespike]

Re: '79 150HP Johnson/22' Starcraft Mariner, What Prop?

Yes a 4 blade will improve low end performance.Stay on plane with less throttle,
plane quicker,handle better both on plane and at the dock.Typically you would drop one inch going to a 4 putting you at a 16"As suggested err on the low side
if you end up under propped you can use it and just watch your rpm.

 

[roughshot]

Re: '79 150HP Johnson/22' Starcraft Mariner, What Prop?

Well I finally finished the boat and got her in the water on Sunday. So here is the data I have so far and not to technical,
She idles and move nicely at low speed, when I giver to get up on plane, I have to put the throttle to WOT. As there is not much weight in the front and I only had 20 gal in her 50 gal take, she stood up on end plowed a little, then planed out. Leaving it at WOT or just a hair back it would climb to about 4200 and top out there. I didn't have a gps so I don't know how fast it was going but it was a comfortable clip, given I was unloaded. Like said befor, I believe the prop to be a 15x17. I think I need to get the rpms up quicker to get a better holeshot and plane out faster. Of course with gear aboard she will probably do better but I don't need a couple hundred pounds of gear slidding to the back on take off.
After reading other posts about tach position switch, I need to check that, the tach is an old tach I got from my mech. And it seems to be operating right.
It just seems like this V-6 should roar a little more.
What do I need to do to get my rpms up?
I will do another test this Sunday and post up my findings. The existing prop is dinged up so I'll be buying a new prop anyways, just want to get a better performer.
If you want to look at the boat set up, check in restores for a 22' Mariner project underway.
Thanks.

 

[roughshot]

Re: '79 150HP Johnson/22' Starcraft Mariner, What Prop?

Last week I picked up a 15 1/2" x 15P prop from my mechanic.
I was able to test it last night.
No I didn't get any serious data but the boat popped up on plan at about 2500rpm which it took 4K with the old 14" x 17P.
it cruised nicely at 3800 rpm and I got WOT at 4800rpm.
I think it was just the right prop for the job.
I will keep an eye out for a 15" x 16P to do some comparisons with next spring, but for this season, I think this one will work great.