Can anyone tell me what I have?

[backyardangler]

Have a new boat. Motor seems fine but I really had trouble getting on plane. I suspect I have too much prop. The best rpm I could get was 4100 with the trip fully down. Then against a stiff wind with the tilt up a little I only got 3500 rpm.

The boat is a 16 foot flats skiff with a 1995 40HP Force.

The only inscription on the prop is 48 73142 A40 16F (or maybe P)

I suspect I need a 10 3/8 x 12. Any help is sure apreciated.

 

[backyardangler]

Re: Can anyone tell me what I have?

OK, I found this on the Merc site. It's a 10 x 16 I guess. That seems awfull coarse pitched. It got on the step really slow. Suggestions??

Any opinions on the Vortex props? They seem much more innexpensive. I need to buy two eventually.

 

[inPursuit]

Re: Can anyone tell me what I have?

You will want to reduce your pitch perhaps to a 13 pitch to get the boat up on plane quicker and also allow the motor to run to it max rpm at wide open throtle (WOT). I might even want to try a 4 blade depending on the boat type.

 

[steelespike]

Re: Can anyone tell me what I have?

Motor is rated at 5,000.Most shoot for 300 to 500 higher.
Each inch change in pitch nets "about" 200 rpm.If you drop to a 12"
it would put you at "about" 4,900.
You might take a look at the Turning Point Hustler props.They deliver close to SS performance at AL prices.Once you have the hub; props are reasonable.
If you start with a 12 you can go up or down as needed.
Before any prop changes you might try raising the motor.
The ativent plate (just above the prop) even with the bottom is a starting point. most motors will run about an inch higher.An inch could get a couple of mph with no other changes.Then the Hustler might allow even more height. You should make only one change at a time.Its easier to evaluate each change.

 

[hwsiii]

Re: Can anyone tell me what I have?

Angler, I have a 2003 Sundance 16KFLX flats boat with a 64" beam, with a 1995 Force 40 and I am running an Apollo stainless 10 3/8" x 14". I am getting 30 MPH with GPS at 4,750 RPM with total boat weight of 1,570 # people and all. But with the rake and cup in this prop it performs like a 15" with the same speed numbers. Hope this helps.
You didn't mention your speed, what is it.
If you stay with the same model prop you have now, these are the results for changing to a 13" pitch.

H

 

[backyardangler]

Re: Can anyone tell me what I have?

Thank you all so much for your help. Advice will be acted on ASAP and results will be posted.

I don't know how fast I'm going, no GPS or speedo. I'm and experamental aircraft builder and have done this with plane props. I know that a fixed pitch on takeoff is only going to make you about 2000 rpm's on takeoff, so you are taking off with about 80% HP. So by me lugging my boats engine I'm only getting about 30 HP since I can't get best rpm to make best power.

Thanks again for the help.

Eric

 

[backyardangler]

Re: Can anyone tell me what I have?

Angler, I have a 2003 Sundance 16KFLX flats boat with a 64" beam, with a 1995 Force 40 and I am running an Apollo stainless 10 3/8" x 14". I am getting 30 MPH with GPS at 4,750 RPM with total boat weight of 1,570 # people and all. But with the rake and cup in this prop it performs like a 15" with the same speed numbers. Hope this helps.
You didn't mention your speed, what is it.
If you stay with the same model prop you have now, these are the results for changing to a 13" pitch.

H

BTW, it's great to know someone with the same motor. Sure hope yours has been a solid performer.