Prop help

[clutch3752]

Hi All,
Looking for some educated advice on proper prop for my new boat. Recently bought a Polar Saltwater series boat. It's 18'6" and 8'ft wide. She came with a 115 four stroke Yamaha. Only took it out once and it has a lot of bounce and the rpms are only turning 4,600. I looked at the current prop and it appears to be a 21 pitch. Been doing lots of reading, but I need someone to make some sense of this to me. If I put a 17pitch on this boat will it keep the bow planted and pick up rpms? Any and all info would be of great help,
Thanks

 

[steelespike]

Re: Prop help

Ok, does it bounce on the waves or porpoise?Have you adjusted the trim.
Have you tried moving some weight forward.
What is the boats weight? typical load?Load as tested?What was speed at 4,600?
Without rpm and speed can't tell where your at?
Shooting from the hip it does appear you have too much prop; you probably need something like a 17".But lets not make any changes without more info.

 

[clutch3752]

Re: Prop help

Hi steelespike, thanks for replying. The boat was porposiing quite a bit. I tried the trim but got worse with it. I had two people on board, it's rated for 6 or 1,350 lbs. The previous owner put 2 fifty pound sand bags in the front to hold it down. I wanna install those smart tabs but I am looking for some help with this prop and rpm issue first. The local marina guy said it's to much prop for this boat, i.e. more like a bass boat prop. Ideas??

 

[steelespike]

Re: Prop help

Would be nice to have your speed at 4,600.A 4 blade prop would give more stern lift
and my eliminate the bounce.Will also get on plane faster and stay on plane with less power. Is the boat a Polar or Polarcraft and what year.Or do you know the weight?Couldn't find boat with a brief search.Do you know the max rated rpm of the Yamie?I'm guessing close to 6,000.
I think a 4 blade 17 would struggle to get you to 5,400.H may check in with some help.

 

[clutch3752]

Re: Prop help

The boat is a Dynasty/Polar, 2000 model. The CG tag has it as a v1700. I can't find it's specs anywhere either. NADA guide doesn't even list it, but the other 2 18 footers they do list have a hull wt. of 1,425 and 1545 lbs. This is a V style boat not a skiff or bay boat. I wish I had they speed, but just have a tach and no gps.

 

[steelespike]

Re: Prop help

Not having anymore info your motor will surely be better off with a Solas Amita 4 blade prop. in a 17".May not be ideal but surely better than making it struggle with a 21.Just be sure it doesn't over rev.