Prop Q
- Thread starter Car Biz
- Start date
When my 272 was "bone stock" I had 25 Miarages but I had 330/454s. A lot of people I know are changing to Bravo 4 blades. One friend has a 1991 242 LS /502 Mag went from a 23 Mirage to a 24 Labbed Bravo and picked up 1 mph top end because he could now trim higher without losing the bite on the water. The most amazing thing was at 4000 rpm he picked up 6/7 mph and at 3000 rpm 5/6 mpg gain(all gps readinggs). Last summer he tried a stock 22 Bravo and lost 1 mph top end but still picked up midrange speed. That's the most important to me because that's where i run mine most of the time anyway.Car Biz said:
Normally when going from 3 to 4 blades you go DOWN one size in pitch because of the additional blade area and better "bite" iin the water.
It's hard to say what the best prop is. What it comes down to is which one works best on your application and that usually involves trial and error :
Ok thanks, the most importand thing for me is the same like yours, the mid range (cruise speed) i would like to get the best performance there. so the told me to swap to a gear ratio of 1.50 so i could turn a bigger prop with less slip, i think bravo three is the best for me ore blackhawk drives?
Heres what I know about props. This applies to 3 and 4 blade.
Pitch is the theoretical distance that boat will move forward in inches with 1 revolution. ex. 22" prop will push boat forward 22" with 1 revolution.
Usually going up in pitch 1 level will reduce your RPM by 200. Going down will increase RPM by 200. Depending on what you want, out of the hole or better cruise or top speed depends on pitch. Or if you boat spec is 4200rpm WOT and you are only getting 4000rpm you could go down.
Go up in pitch you loose a little out of the hole and gain top end and cruise. Go up to much hardly get on plane with out sending someone to the bow and also you may not be able to get the rpms high enough to reach the sweet spot.
Go down to much, pop out of the hole and redline before you hit cruise.
These are extreme examples and its a trial an error thing. Best time to trial is in the begining of the seanson when a few of your buddines boats are still up for the winter and borrow their props. Otherwise its expensive.
My 31 PC has 28" props and tops out at 4200 rpm at 50 mph. I know I can spin the motors up to 4400rpm, but I like the 32mph cruise at 3100 RPM at 30 Gph.
:
Pitch is the theoretical distance that boat will move forward in inches with 1 revolution. ex. 22" prop will push boat forward 22" with 1 revolution.
Usually going up in pitch 1 level will reduce your RPM by 200. Going down will increase RPM by 200. Depending on what you want, out of the hole or better cruise or top speed depends on pitch. Or if you boat spec is 4200rpm WOT and you are only getting 4000rpm you could go down.
Go up in pitch you loose a little out of the hole and gain top end and cruise. Go up to much hardly get on plane with out sending someone to the bow and also you may not be able to get the rpms high enough to reach the sweet spot.
Go down to much, pop out of the hole and redline before you hit cruise.
These are extreme examples and its a trial an error thing. Best time to trial is in the begining of the seanson when a few of your buddines boats are still up for the winter and borrow their props. Otherwise its expensive.
My 31 PC has 28" props and tops out at 4200 rpm at 50 mph. I know I can spin the motors up to 4400rpm, but I like the 32mph cruise at 3100 RPM at 30 Gph.
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You just about covered it all. I didn't feel like typing that much ;D.
Car Biz, I don't know why Bravos would tear up your Alphas. You don't have a ton of HP with stock 350 mags. A friend of mine ran a 406 sbc dynoed at close to 500 hp for years thru his Alpha in a 20' bowrider. Easy on the sticks and you should be OK.
I like my 50mph at 3000 8)
Car Biz, I don't know why Bravos would tear up your Alphas. You don't have a ton of HP with stock 350 mags. A friend of mine ran a 406 sbc dynoed at close to 500 hp for years thru his Alpha in a 20' bowrider
. Easy on the sticks and you should be OK.I like my 50mph at 3000 8)
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50 mph is a walk in the park. 65 it's a thrill , 75 starts to get your attention , over 80 is a little crazy since my hydraulic steering is still in a box in the garage and not on the boat yet.
Wakes under a foot you don't even notice. I've gone over RR tracks that were rougher. 2 feet I'll slow down.
At 50 probably the back third of the boat's in the water. WOT and trimmed up maybe the last two feet or so is wet
BTW over 80 you steer very little. You more or less just aim the boat
Wakes under a foot you don't even notice. I've gone over RR tracks that were rougher. 2 feet I'll slow down.
At 50 probably the back third of the boat's in the water. WOT and trimmed up maybe the last two feet or so is wet
BTW over 80 you steer very little. You more or less just aim the boat
Cuda said:
Pepto Bismol specials ;D ;D ;D.
Drive problems...no , thank you very much because now I've probably just jinxed myself :'(. I always ease into the throttles(NO STRAIGHT ARM HOLESHOTS) and I try not to catch too much air. But then again it's not often I run over 70 and when I do it's usually for short bursts. I also have a spare in the garage
BTW Joe , My boys are big enough to where pink ;D ;D.