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PROP CHOICE need help

H

Hotrodboat

New member
I have an 1989 Checkmate vision, 468 BB Chevy, MSD, quadrajet carb, through hull exhaust, bravo1, NO TRIM TABS, currently has a stainless 25p mirage 3 blade. Looking for a good towing prop, high speed prop, or best all purpose prop.

Any ideas on whatI should run?
 
Wow. That is waaaay low on rpm! Are you trimming drive up at speed? Heck, stock 454 with peanut ports were made to spin 4600 or so. Mags up to 5000. Either you are way over propped or have a really really mild 468
 
That's why I was thinking I need a lot smaller prop. Maybe like a 21 or 23. I'm also going to check and see if the throttle is opening up all the way.
 
rpm seems extremely low.
Would recommend dropping way down in pitch if the engine is running strong and right. But it doesn't sound right.
You should be able to turn a 23 to wot easily (nearly 5000ish rpm?).
Have you tuned and checked out the engine recently?
 
Your tach seems correct based on your MPH. So that means your motor is not turning the RPMs it should. I think the 468 was a bored out 454? The 25 Mirage should be the right prop and the boat should be doing mid 60's. If you drop to a 21p prop you'll get the revs up but you'll still be in the 50's not 60's.

My 320hp 6.32L turns a 23 Mirage to 4900 and gets me to 60 mph.

Because it sounds like it is running fine maybe it is something simple like the throttle linkage not opening the carbs wide open. That would be my first check.
 
Correct. 454 bored to 468. When I get a second hand i'll check the linkage and see if its opening up all the way. I'll post my result.
 
ok checked the linkage. It was fine. Got the suffix code off the back of the block and looked it up. 3999289. Its a 1972-1978 454 2 bolt main 215,235,240,270. I have paper work the shows this engine was rebuilt in 2011 and bored 40. over. Valve pockets opened up. Keith black rotating assembly. Has cast iron heads not sure what kind.
 
I can only guess what the horsepower is. I tried the 27P 4 blade just for the hell of it and at WOT it turned 3600rpm at 50 mph on my cell phone gps app. I talked to a prop shop and they recommended the following props. Stainless 3 blade mirage 21p for towing, stainless 4 blade bravo 22p for best all around, and a stainless 3 blade mirage 23p for top end speed.

What are your thoughts?
 
Hotrodboat said:
I can only guess what the horsepower is. I tried the 27P 4 blade just for the hell of it and at WOT it turned 3600rpm at 50 mph on my cell phone gps app. I talked to a prop shop and they recommended the following props. Stainless 3 blade mirage 21p for towing, stainless 4 blade bravo 22p for best all around, and a stainless 3 blade mirage 23p for top end speed.

What are your thoughts?
Click to expand...

Dumb question and I only ask because I've done it. Are you sure you're trimmed up as high as you can be? I couldn't get over 4000 rpm until I realized if I trim up almost until or until there is a rooster tail then I was able to get it to 46-4700
 
Hotrodboat said:
I can only guess what the horsepower is. I tried the 27P 4 blade just for the hell of it and at WOT it turned 3600rpm at 50 mph on my cell phone gps app. I talked to a prop shop and they recommended the following props. Stainless 3 blade mirage 21p for towing, stainless 4 blade bravo 22p for best all around, and a stainless 3 blade mirage 23p for top end speed.

What are your thoughts?
Click to expand...

OK, I thought you had a bored over performance 454.
So, maybe the prop is just too much. The carbed 454's were 310hp at the prop. I doubt the overbore would add much to that. The 25p Mirage would be too much prop and is maybe just bogging the motor down. A 23p will only get you to 4100-4200. Not enough. You want to get to 4400 so you will need a 21p.
Check the gear ratio on the right side of your drive. They were usually 1.65 with that combo. If that is the case the 21 Mirage is likely the right prop. The slow reving 454's with 1.65 gears do much better with a large diameter prop. The Bravo 4 blade should work as well.
See if you can try before you buy.
 
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