3 blade or 4

[randlemanboater]

Originally Posted by smokeonthewater

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

That has been my experience as well...if your prop turns too many rpms at wot then your holeshot should be neck snapping.

[smokeonthewater]

first reply on iboats
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. (antiventilation) 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?

soooo yeah what is the motor height and top speed is gonna be an important key in solving this issue.

[smokeonthewater]

whoops... double post

[steplift20]

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 differance 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

[randlemanboater]

I'm betting that the tach is reading wrong.

[smokeonthewater]

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

I agree with him... I posted your last comment just now.

I suggest checking out the tach.... maybe obtain another for testing purposes.

[steplift20]

so what im hereing is that the prop is the correct size and its the tack thats giving wrong reading, well i will serently look into that and i will get back to you and let you know what the outcome is thanks for all the help
this problem will get correccted for sure

[smokeonthewater]

we are not certain of anything yet but we feel that the logical next step is to verify rpm and gps speed.

My calculations came up with a lower pitch prop but that would raise rpm's..... The only thing we can say for sure is that your stated rpm, speed, pitch, and engine do not match up.... there's a skunk in there somewhere and we need to find him.

THEN we can recommend a prop for ya.

[smokeonthewater]

we are not certain of anything yet but we feel that the logical next step is to verify rpm and gps speed.

My calculations came up with a lower pitch prop but that would raise rpm's..... The only thing we can say for sure is that your stated rpm, speed, pitch, and engine do not match up.... there's a skunk in there somewhere and we need to find him.

THEN we can recommend a prop for ya.

[Stinky_Hooker]

I did the exact thing you are considering on my 18 and did not like it. I had a new 4 blade stainless given to me. I lost about 6mph top end with a little better whole shot. It went in the bow for a spare and my 3 blade Stilletto went back on the motor.