Prop Advice?

[josh_scci]

OK so here is the problem. Weak hole shot at full payload! The boat has a good hole shot but add 275lbs and it takes 30 seconds or so to get on plane also the boat doesn't like to stay on plane if let off the throttle at all.

Details
Don't know prop manufacturer but I think it is the original prop that came with the motor. But it is an Aluminum prop.

Prop diameter and pitch unknown as it has no markings anywhere I can see but I do not have a prop wrench so it could be on the back.

Wide open throttle is about 5000. Average speed at full load is 29mph.

Motor is a 1988 Johnson 40hp VRO outboard.

Boat is a 1987 Ozark F141 fisherman modified tri-hull. Length is just over 14'. Weight is 495lbs dry and about 1300lbs fully loaded including motor gear fuel and people.

Any advice?

 

[josh_scci]

Re: Prop Advice?

I finally pulled my prop off and this is the OMC# 0390851 RH SS 11 3/4 x 17

Can someone give me any advice?
Also does the SS mean stainless steel? Because the prop is heavy but has a black powder like coating on it.

 

[steelespike]

Re: Prop Advice?

SS could be stainless.If stainless it will liklely be at least slightly magnetic,
if al not magnetic.Your antivent plate (just above the prop) should be visable on plane. 17 is pretty high up the chart.Your are doing prettywell considering the pitch and load.A 15 should add "ABOUT" 400 rpm and increase your hole shot.
If you have ss and go aluminum the results will vary unpredictably.
If you go to a 17 watch your rpm with a light load.
You could have a ss repitched for a little more than a new aluminum.

 

[josh_scci]

Re: Prop Advice?

I will have to try a magnet on it to see if it is stainless or not. Also I already have a 17 on it so why would I need to watch the rpm with a light load. All I want to do is improve the hole shot and be able to keep it on plane at lower speeds.

 

[josh_scci]

Re: Prop Advice?

OK so it is a stainless steel prop. So I am thinking of sending it in to a prop shop to have it fixed and possibly re-pitched. Would I be better off at a 16" or 15" pitch? Also can nicks in the prop be cleaned up and is it worth it? And does anybody know of a decent prop shop?

 

[steelespike]

Re: Prop Advice?

I got confused thought it was bigger I guess. Reducing the pitch 2" should result in
an increase of "ABOUT" 300 to 400 rpm putting you close to your rated rpm.
Improve hole shot and help stay on plane.A ss is more to modify than aluminum
it can be cleaned up. A 15" Solas Amita 4 blade aluminum should vastly improve hole shot and ability to stay on plane at reduced throttle.Probably for about what the ss mod would cost.4 bld would also improve handling on plane and at the dock.
Top end would be likely reduced.If you have tanks and batteries in the stern moving some of that forward would also help.Trimming in a notch would help as well.

 

[josh_scci]

Re: Prop Advice?

I found a guy online (Dans Prop Shop) who will repair and re-pitch for 120 on my current prop I am just not sure if I should go all the way to 15 or maybe try 16 first. Also I don't really have anywhere else I can put the tank and batteries besides the stern I could build a place to put the tank nut it would move it about 10 feet from the motor and I didn't think you could do that.

 

[steelespike]

Re: Prop Advice?

Tank distance from the motor isn't a problem.I put my tank right at the bow of my Crestliner 18 ft utility. No problems.
Distance really doesn't matter within reason raising the fuel vertically is harder than relatively level distance.With the tank forward the vertical lift is likely less than with the tank at the stern.