What Prop is next

[sledhead26]

I had a stock aluminum 21 pitch on my 115 Mariner and caught a couple rocks. So while that was being fixed I put on a Ballistic 21 pitch stainless prop and now I run too many Rpm's. It's about 200 rpm over the suggested range. I'd like to stay with the stainless but do I need to go to a 19 or a 23. The stainless prop was really good out of the hole. I just want something thats good all around. Any info would be appreciated. Thanks

 

[hwsiii]

Re: What Prop is next

Theoretically you would go to a 23" prop and lose about 400 RPM but gain speed over what you have now.
If you could give me this information it would help though;
WOT RPMs range recommended by manufacturer
Gear Ratio on your motor
WOT RPMs with old prop
WOT RPMs with new prop
Is speed by GPS or other
WOT Speed with old prop
WOT speed with new prop
Manufacturer and Model of boat
Weight with motor fuel and gear on board
Is it flat bottom or Vee and how much Vee
If you would give me this information I could give you a better indication of expected speed and RPMs


H

 

[hwsiii]

Re: What Prop is next

Duplicate

 

[steelespike]

Re: What Prop is next

What he said^^.We really need all that nitpicky info.
Sometimes folks seem to be secretive about their specs.

 

[a70eliminator]

Re: What Prop is next

I have my 20' foot bow rider proped with a 14-1/4x18P it puts me about 200RPM over the limit, but thats just me in the boat and i just back off throttle a tad, but I can pull a big kid on a tube fully loaded with 5 or 6 people without lugging and thats what we do most, very seldom would it be just me, I have my little boat for that.

 

[sledhead26]

Re: What Prop is next

Ok boat is a '94 sylvan pro select 19' which is a deep vee
Total weight with gear motor ect. is close to 2000lbs
Motor is '94 Mariner 115 with a 2.07 gear ratio
Recomended Rpm range is 4800-5250
WOT with old prop is 5000
WOT with new prop is 5400
WOT speed with old prop is 35
WOT speed with new prop is 40
Speed probably is not quite as accurate because that is based off speedo not gps. Thanks in advance for all your help.

 

[steelespike]

Re: What Prop is next

If your 200 over alone I would stick with the 21.Just stay out of it a little.
Normally you would increase pitch (higher number) to lower the rpm but the 23 would probably drop you about 400 putting you too low.If you could find a 22 would put you close. Rule of thumb about 200 rpm per inch of pitch.Assuming similar type props.

 

[sledhead26]

Re: What Prop is next

Ok, thanks I was thinking of doing just thats. Wasn't sure how much the 23 would lower the rpms. Thanks

 

[hwsiii]

Re: What Prop is next

Sled I show in my calculations you should be doing 47 MPH at about 5,050 RPMs with the new 23" Ballisitic prop with a 10% Slip. Hope this helps.

H

 

[hwsiii]

Re: What Prop is next

The only problem I find is that the Slip on your 21" Ballistic you are running now is over 23%.

When you make runs at WOT be sure and make 1 run in 1 direction and then turn 180 degrees and make a run in that direction; Add the two numbers together and divide by two to get the truest speed.



H

 

[Eshaw150]

Re: What Prop is next

If your 200 over alone I would stick with the 21.Just stay out of it a little.
Normally you would increase pitch (higher number) to lower the rpm but the 23 would probably drop you about 400 putting you too low.If you could find a 22 would put you close. Rule of thumb about 200 rpm per inch of pitch.Assuming similar type props.

i have an 89 travaler cc 20 ft
has a suzy 140 2 stroke fully loaded it might be about 3-4000 pounds
running at 4000 rpm it is only runnin 20 about 2 nots had a 150 on it with i higher prop and it planed it out and moved it better
it has no a 17 p prop and had a 19 pitch

so i need to lower the rpm so do i need to go to a higher pitch

 

[steelespike]

Re: What Prop is next

First you should start your own thread.Its too confusing to all involved.
I can't figure out what you have going on.We need description of the boat
deep V semi V flat bottom?
more accurate weight,need motor with max rated rpm, prop size (stainless or aluminum) with the max rpm and speed.If your running 2 different motors we need details for each.

 

[Eshaw150]

Re: What Prop is next

it posted under wrong pitch

 

[sledhead26]

Re: What Prop is next

Thanks Hwsiii. I'll make a few more runs to try and get it a little more accurate.

 

[hwsiii]

Re: What Prop is next

Ok Sled.