1996 Johnson 40 HP WOT 6400 RPM

[RyanB11]

All,
I have a good understanding of props as far as RPMs/pitch and diameter. However, This one is tricky. Just rebuilt a 16' Privateer bay boat. I have a 1996 40hp Johnson with an aluminum Turning Point 12 1/4 X 15 prop. I put a CMC trim/tilt bracket on. The bracket sets the motor approximately 4" higher and 5" back than mounted on the transom directly. This is for water flow that pops up from the keel installed as directed by CMC. I need to get the RPMs down to around WOT 5800. Right now I'm at WOT 6400 and can top out at 24 knots. Was going to try a 11 3/4 X 17? Any other ideas? Thanks. New to the site, A lot of great point of views. Ryan

 

[steelespike]

Re: 1996 Johnson 40 HP WOT 6400 RPM

A 15" prop is pretty far up the list.6,400 rpm and only 24 knots What is the mph conversion?
Is this boat really light?I think either you have a lot of slip or the tach is wrong.
The Hustler is really agressive and isn't likely to have slip problems.

 

[RyanB11]

Re: 1996 Johnson 40 HP WOT 6400 RPM

The boat is just under 1000 lbs. fully rigged. I did part the tach off another boat however it seems to be responsive thro ughout the entire range of throttle. But it couldn't hurt to throw another one in there. The boat goes about 26 mph. Thanks

 

[steelespike]

Re: 1996 Johnson 40 HP WOT 6400 RPM

Good plan.
There are only 3 props bigger than the 15.I don't think a 40 is going to turn
a 15 at 6,400 on a 1,000# boat and on top of that only go 26.
26 may be in the ball park for speed but not at 6,400.