[rainman55343]

Hey guys wanted to what rpm am I supposed to run at top speed. Don't remember gear ratio on my alpha drive. I got a 19p 4 blade as now. If I go to a 4 blade 21p as what would it do.

[rainman55343]

Ss to ss prop

[rainman55343]

And has the 5.7 2 barrel carb

[ColoradoDiablo]

Max is at 4600 - 4800rpm.
If you go up in pitch to the 21 , your going to loose about 400rpm.
So say your running at 4700 now you'll be at around 4300 with the 21. Plus , your going to see a noticeable loss in your "out of the hole" planning performance.
If your going over the max WOT , then I'd definately get the 21 , but I bet your not.
If you want more top end , go to a 3 blade prop.

[rainman55343]

I might stick with the 19 then. My marina said a 4 blade is good for hole and top end. He said u lose a couple mpg with a 4 blade. I will have to wait and see. Can I have full throttle for a few seconds and see. Remember its a new motor and I have to break it in. I want to go around 60 and have a good hole shot.

[ColoradoDiablo]

Started different thread so more members with your setup can chime in

Yeah , I'd take it easy on her for at least the first 15-20hrs , but that's just me.
You loose a couple MPH with the 4 blade , but I wouldn't trade mine for nothin'!
I don't think you'll be happy with the holeshot with a 21p.

[rainman55343]

K will do thx again. I like the hole now.it should go about 60 right. I mean that's a big motor in a 19 foot boat. The most u could get was a 5.0 in it.

[ColoradoDiablo]

According to the 2003 brochure she would run 49-52 with the 5.0. You got to remember , that is with a 3 blade prop ,a couple people , and maybe a 1/4 tank of fuel.
I think you'll get close to your mark , but the 4 blade will cost you a few MPH.
How fast have you had her? At what RPM?

[rainman55343]

I had it at around 52 at 3/4 throttle. Remember I got a 5.7 now not a 5.0. I should have 250 to 260 horse now compared to 220.

[rainman55343]

Don't remember rpm at 3/4 throttle