help me reccommend a prop for a fellow on another forum

[smokeonthewater]

I put the same questions to him that we have on the sticky and here are his answers... whacha think?

1) Performance issue you are trying to correct.--- get on plane faster and lower rpms to with in range 5800
2) Current prop manufacturer, model, aluminum or stainless as a minimum.--- aluminum, 13x19 its the prop that came with the engine
3) Current prop diameter and pitch (required)---. 13x19
4) Wide open throttle RPM and speed with an average load (very helpful) ---6400 rpms
5) Engine/drive make, model, year, and HP--- yamaha 4 stroke 2003 115hp OB
6) Boat make model, year, length and weight"--- 19 foot polar 2003 about 2000lbs center console

He's looking to go to a 4 blade prop and doesn't mind losing a little top end speed ...... also does 13" diameter sound small?

 

[smokeonthewater]

Re: help me reccommend a prop for a fellow on another forum

he also said "wot is 6300 it should be 5700 plus its hard to get her to plane, im not looking to go faster just lower the rpms and bring the bow down faster. i think the biggest diameter is 14 that i can go"

 

[smokeonthewater]

Re: help me reccommend a prop for a fellow on another forum

his numbers just don't add up for me.... below is my last comment for him... I'll post his reply when I get it.

"Are you certain that your tach is correct? I have been running some prop calculators and am coming up with a lot lower pitch than you have now.
what is your current top speed?

any chance that your hub is slipping or that your prop is ventilating?

Such a high wot rpm should go hand and hand with a dynamite holeshot."



btw fwiw iboats IS getting credit there

 

[steelespike]

Re: help me reccommend a prop for a fellow on another forum

Unless I missed it I didn't see a wot speed.A brief check of Yamaha performance bulletins
a 20 ft11" Polar Craft CC with a 115 using a 13 X 19 al prop 2500 lbs ran 38 mph @ 5850
0-20 5.25 seconds. Plate is 1/4" above the bottom It seems his setup is right though perhaps check the height.
Does he trim down for hole shot?

 

[smokeonthewater]

Re: help me reccommend a prop for a fellow on another forum

wot speed is a question I asked last night... still waiting on an answer... I'll relay this too.

 

[steelespike]

Re: help me reccommend a prop for a fellow on another forum

A 19" prop at 6300 makes about 50mph.@ 6% slip.
As I'm sure you have figured, not likely.
I suspect the tach.

 

[smokeonthewater]

Re: help me reccommend a prop for a fellow on another forum

here is his latest reply:
"its my sons boat and i think he said 34mph,but he did tell me that when its about 3/4 of the way down the throttle and puts it all the way down he sees no difference in the speed. its a white prop that came with the boat, probably not a very good one but an all around prop, and it tachs out at 6400rpms, to high"

I too suspect the tach.