prop help
 

Ok here's the details. 27' Mach 1. 500 hp 454. Bravo 1 drive. When running a 3 blade 19 p I was running 5800 rpm After changing to a 4 blade 22p I can only get to 4200-4400 rpm. The boat is faster with the 22 p but seemed to have lost a lot of rpm. Engine builder says the max hp is at 5200 and the max rpm 5600. Which prop should I try next?

What kind of 3 blade vs what kind of 4 blade??? With 500hp, I would think you should be able to spin a 22"Bravo1 in any 27' boat at 5000r's.:confused:

Not sure on the prop kind. The one came with the boat, (19P) and the other I bought used from someone who had it in the classifieds here at OSO. Just can't get past 4400 with the 4/22p prop. Has been suggested to go back to a 3 blade with 25p. Just don't know which way to go with this. Thanks for your post

If it helps I spin mirage 25 @ 4600 rpm with stock 330 7.4s. I tryed 23'' REV 4s better off the line but the same rpm. Sounds like you should be able to spin 22s a lot faster than you are. What is your mph with both the props? With 500 hp a 25 should be a starting point.

No gps and no speedo. But I was next to another boat and he said was going about 65 , but that was with the 22p the 19 p was much slower

Where does your torque start to fall off? This needs to be considered too. I agree you should be spinning the 22 alot faster. You need an accurate tach and a GPS to make a decent comparison between props.

Drive ratio-unknown
Weight-4800 lbs
Torque fall off? No idea

I'll try another tach but before with the 3\19p I was turning 5800rpm. Not sure if the 7.4 will hold together much more than that. And nothing else was changed but the prop. Thanks for the posts.

props
 

Recently made the "leap of faith" switching from 3 blades to 4...we all have our reasons. Merc's website and BAM marine offer some good pointers...Being so close to your redline, simply adding 2 inches to your 3 blades might have been a good starting point. A 21' Mirage may be all you need to drop your rpm and find your balance. "Fastech" is totally correct. Be sure your tach is accurate. You're on the right track with the "prop black art". Ask. Ask. Ask. (Especially if you don't have a small bank at your disposal).

Christian, at my disposal is a marina that will lend me props to try. Just don't want to be running thru there whole stock...lol. Thanks for the post, 88 Mach 1