Prop for Merc 5.7 Alpha 1

[Gfriedman]

1) not necessarily performance, just advice on quality and choice of props.
2) Manufacturer unknown, model unknown, aluminum
3) 13" x 19p
4) 4600, 13moh
5) '99 Merc 5.7 Alpha one. 260 HP
6) Maxum 2300SC 24' 3600

My current prop needs to be replaced, just old and abused from years of wear and tare. Any advice on brands or manufacturers?

I am thinking to stay aluminum. I use the boat to pull up the beach and mostly as transportation with a small amount of water sports.

I have a set of Bennett 12 x 12 trim tabs on the boat. The over performance is fine. If i could improve anything it would be gas mileage, but the top end speed is fast enough and i am happy with the way it gets on plane.

What would the effects of a larger prop do? any thoughts on that?

Thanks,

Garrett

 

[Bondo]

Re: Prop for Merc 5.7 Alpha 1

3) 13" x 19p

Ayuh,... Are ya Sure 'bout that,..??
13" diameter sounds to small for an Alpha...

 

[Gfriedman]

Re: Prop for Merc 5.7 Alpha 1

Those the numbers that they read for me off the prop when i brought it to west Marine.

I double checked again myself and had a really tough time reading the numbers on there.

When i measured, it was a 13" diameter.

 

[Tail_Gunner]

Re: Prop for Merc 5.7 Alpha 1

4. 4600, 13moh...your as bad as me.....Does that mean 4600rpm@13mph???

 

[Gfriedman]

Re: Prop for Merc 5.7 Alpha 1

It seems like the consensus is i am running with too small of a prop. Does anyone have a merc chart that shows me HP and engine size compared to prop size or anything like that? What should i expect in terms of performance if i go to a bigger size?

 

[Bondo]

Re: Prop for Merc 5.7 Alpha 1

It seems like the consensus is i am running with too small of a prop. Does anyone have a merc chart that shows me HP and engine size compared to prop size or anything like that? What should i expect in terms of performance if i go to a bigger size?

Well,... If this Is a 13" diameter prop, it's probably an outboard prop for a midsized gearcase...
Is there a large gap between the lower unit housing, 'n the prop's body/ barrel,..??

Generally speakin',...
Alphas run props of about 14" to 15" in diameter, 'n 15" to 23" of pitch....

My 1st Guess is, you otta be somewhere around a 14.5" diameter, by 17" or 19" of pitch...

 

[75TowerOfPower]

Re: Prop for Merc 5.7 Alpha 1

Better bite and easier to plane. You may lose some of the top speed but it will overall help move that bigger boat of yours. What is your gear ratio on the outdrive?

I have a Crownline 202 with a 5.7L carb and Alpha and 1.62 gears with a 19P prop and the low end is great and still hits 48 MPH. But my boat is 3100 lbs dry and the prop is 14.25" in diameter.

 

[QC]

Re: Prop for Merc 5.7 Alpha 1

I know the boat and that engine combo allthough, for clarity, I think you actually have a 250 hp, not a 260 . . . I ran with a friend with the same and it was pretty much a 42 MPH boat, and if I recall he had a standard Merc three blade aluminum and it pulled a 19.

It would be really cool if you fixed the RPM and speed numbers above. It it is really 13 MPH, or even 31 MPH, then you have bigger issues than a propeller