3 blade or 4

[smokeonthewater]

Got the fellas on iboats workin on it... I have a couple ideas but waiting to see what they think.

[smokeonthewater]

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.

[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.