Looking for some general prop advice please

[fishinstix]

Hi all,

My current prop is alumininum and chewed up so I need to buy a new one. But before I buy the same one I was wondering if I changed the pitch, or went to stainless, I might be able squeeze some more performance out of my boat. So, if anyone has any advice I'd sure appriciate it. I'm actually not unsatisfied with the current performance but if I can get some more......

First I'll answer the standard questions:

1) Current prop: aluminum 1985 OMC (standard with engine)
2) Current prop diameter and pitch: 11 3/4" x 17".
3) Wide open throttle RPM and speed with an average load: 5210 RPM at 30mph (GPS)
4) Engine: 1985 Evinrude 40HP, short shaft, tiller steer, model E40RCOB
5) Boat make model, year, length and weight: Tracker Grizzly 1648 jon boat, 2006, 16ft long, 70" top beam and 48" bottom. Salt water use.

Thank You
Mark

 

[fishinstix]

Re: Looking for some general prop advice please

After reading some other posts I guess I should also add the following info.
The cav plate is about 1" above bottom. Boat weight is around 550 empty. However speed and RPM was taken with two people, 6 gals. of gas and a start battery.
Thanks
Mark

 

[pootnic]

Re: Looking for some general prop advice please

I'm thinking thats pretty good as is...
The 17 pitch prop seems alittle big but if thats your rpms,I can't see to much room for improvement.

I had a 40 hp Suzuki on a 1652(awhile back),used a 15" pitch...went around 33mph but only 1 person and lighter.
Do you plane off quickly with the 17" pitch?
The more I'm typing,the more i'm thinking your speed seems alittle low for a 17"pitch at 5200 rpm but it will depend on the slippage and gear ratio...anyways...

 

[steelespike]

Re: Looking for some general prop advice please

I think your just about right on.5250 at 30 mph indicates about 14% slip the high end of normal.
I think a new Solas Amita 3 blade 17" should do well,maybe improve slip and might add a little speed.
Is the bottom clean and smooth?Is the motor in excellent tune?
Does the motor have a whale tail(hydrofoil) on it? Does the boat respond to up trim?
Do you carefully adjust trim.
Does it have a strong hole shot?
While a Jon gets up on the water easily; sometimes they aren't the fastest design. Many rivets,convolutions and 4 or 5 keels dragging through the water.
Have you eliminated any stray weight?

 

[richardgreen]

Re: Looking for some general prop advice please

Consider spending the money on bigger carbs for more performance instead of a fancier prop...

 

[fishinstix]

Re: Looking for some general prop advice please

I think your just about right on.5250 at 30 mph indicates about 14% slip the high end of normal.
I think a new Solas Amita 3 blade 17" should do well,maybe improve slip and might add a little speed.
Is the bottom clean and smooth?Is the motor in excellent tune?
Does the motor have a whale tail(hydrofoil) on it? Does the boat respond to up trim?
Do you carefully adjust trim.
Does it have a strong hole shot?
While a Jon gets up on the water easily; sometimes they aren't the fastest design. Many rivets,convolutions and 4 or 5 keels dragging through the water.
Have you eliminated any stray weight?

Bottom is clean (welded, no rivets). Four smooth keels.
Semi V hull.
Engine in tune great.
Hole shot good with 2 peeps, weak with 4.
No hydrofoil or tabs.
Manual trim (trim pin) best performance lower unit set at 90 degs. perpendicular to bottom.
Weight as tested: boat 550, engine 200, people 370, battery 20, gas 30. Total - 1170 lbs.

 

[fishinstix]

Re: Looking for some general prop advice please

Consider spending the money on bigger carbs for more performance instead of a fancier prop...

Interesting prospect.....do you know what carbs I could upgrade to? Is it a simple bolt on new carb type of mod?My motor is a stock E40RCOB.

 

[steelespike]

Re: Looking for some general prop advice please

Interesting it appears the 40,50,55.and 60 have the same displacement.45 cu in.
Of course there must be some major changes.Someone should be along with that info.
A 40 to a 50 might be easy but usually the best way out is to trade up.