Prop for my 383 liberator

[86liberator]

So I got my 383 in the mail and it is being installed as I speak. The engine puts out approx. 360 horse which is about 100 over my stock 350/260HP. My boat is a 211 liberator. My current prop is a mercury mirage 21P which would spin the old engine at about 4600 rpm at about 48-50mph. I know my old prop won't be enough so I was thinking a Mirage 23 Pitch? I would like to be able to hit 60 mph with this new combo. What do you think? thanks

 

[Bondo]

Re: Prop for my 383 liberator

What do you think?

Ayuh,... I think this is a Prop question that belongs in the Prop Forum....

 

[180shabah]

Re: Prop for my 383 liberator

We can talk about the drive you are putting behind it, and at what RPM that 360hp is being made, but like Bondo said prop talk needs to be in the prop forum.

 

[86liberator]

Re: Prop for my 383 liberator

I am going to reuse the alpha. I am having it all gone through and a drive shower installed. I'll just take it easy on the hole shots. The 360 HP is just an estimate. Probably making that power at about 4600-4800 rpm.

 

[180shabah]

Re: Prop for my 383 liberator

If you don't know how much power, and at what RPM it is being made, you will not even get a good guess, for the prop.

 

[86liberator]

Re: Prop for my 383 liberator

If you don't know how much power, and at what RPM it is being made, you will not even get a good guess, for the prop.

The engine a fairly stock 383 which was rated at 340 HP. I had the engine shop put a slightly larger cam and I am going to be running this engine with headers so that is how I came up with 360 HP. The engine builder told me the max rpm should be 5000 but to try and keep it around 4600-4800. So I am probably going to be close to about 100 HP over stock

 

[svilla]

Re: Prop for my 383 liberator

So what is your target RPM @ WOT? 5000 or 4800? I would run the old prop and get some performance numbers (after the engine is broken in as per the builder) then go from there.

 

[hwsiii]

Re: Prop for my 383 liberator

Liberator, I need to know the Gear ratio for your outdrive so I can run some numbers through my program.

H

 

[Mkos1980]

Re: Prop for my 383 liberator

My engine is identical to carcrafts buildup in EVERY way except they used a 750 Holley and headers. They came in with 404HP and 438 TQ. Out boats are about the same size and weight and you can see my MPH in the sig with the prop I used.

 

[86liberator]

Re: Prop for my 383 liberator

Liberator, I need to know the Gear ratio for your outdrive so I can run some numbers through my program.

H

I have the stock alpha one from 86 so whatever the gear ratio was, I am not sure

 

[86liberator]

Re: Prop for my 383 liberator

My engine is identical to carcrafts buildup in EVERY way except they used a 750 Holley and headers. They came in with 404HP and 438 TQ. Out boats are about the same size and weight and you can see my MPH in the sig with the prop I used.

Wow 65 is pretty impressive. I'm probably not making quite as much power so 60 is probably doable. Sounds like a 23P prop is probably the way to go.