Performance Boats Forum banner

1 - 15 of 15 Posts

·
Registered
Joined
·
390 Posts
Discussion Starter #1
I currently have a 24 p Bravo I prop on my 24 ft Deck boat with a Bravo I drive. I am only turning it 4500-4700 RPM (Tack connections are loose, so I don't really know) and running right around 58-62 mph on gps. We boat at 4400 ft and typicallly see the density altitude in the 6000-7000 ft range. I am thinking of going down in pitch to try and get the RPM up some to make more power. The motor is a built 523" and can handle the RPM, what can the drive handle?

I think the gear case has 1.50 gears is it better to change the gears to 1.65 or just change the prop? How hard is it to change the gears?

If I have to buy a new prop is there something other than the Bravo 1 that I should be looking at? Anyone got something used your interested in selling?
 

·
Diesel Pimp
Joined
·
1,256 Posts
Good question!!

I run mine up to 7000, It's been two years worth of hard driving and so far nothing has broke. I'm not an expert, but from I've been told low RPM torque hurts drives more than high RPM. I do watch the magnets on the drain plug and change the oil fairly regularly. And it's looking good so far.

Would love to hear from one of the experts. HUllshot built my drive, this will be the third long season of being easy on it:wink2:
 

·
Scarab 22
Joined
·
142 Posts
you are probably turning it faster than you think especially since your tach is acting goofy with loose wires. mine turns 6k all day long with the same prop and drive
 

·
Registered
Joined
·
317 Posts
I currently have a 24 p Bravo I prop on my 24 ft Deck boat with a Bravo I drive. I am only turning it 4500-4700 RPM (Tack connections are loose, so I don't really know) and running right around 58-62 mph on gps. We boat at 4400 ft and typicallly see the density altitude in the 6000-7000 ft range. I am thinking of going down in pitch to try and get the RPM up some to make more power. The motor is a built 523" and can handle the RPM, what can the drive handle?

I think the gear case has 1.50 gears is it better to change the gears to 1.65 or just change the prop? How hard is it to change the gears?

If I have to buy a new prop is there something other than the Bravo 1 that I should be looking at? Anyone got something used your interested in selling?
what is the red line or max RPM on your motor an how much HP an how much weight or passengers do you have in the boat with you I run a 28ft cat single 525 merc an 1.50 ratio with 5 people an a 26p 4 blade bravo 1 I can turn it to 5400 getting 68-70 mph then I can run 28 4 blade by my self low on weight I get 80 mph out of it at 5400 that's at the red line
 

·
Registered
Joined
·
390 Posts
Discussion Starter #5
Thanks for all the feed back. Sounds like the drive will handle more RPM just fine. I need to find a 22p bravo 1 prop now. The motor should be good to 6500+ no problem. Seems like the boat should be faster than it is and thats what I am trying to figure out. Any one got any idea what a 1991 24 ft elimator fun deck (or Daytona) weighs? The 58 mph last weekend was with 5 people and 50 gallons of gas so we were very loaded down, and plug 58 into the prop calc at 15% slip and it confirms its only spinnng 4500 rpm.



I am thinking if I can get the RPM up some the motor will start breathing better and make more power and hopefully pick up some MPH.
 

·
Registered
Joined
·
317 Posts
Thanks for all the feed back. Sounds like the drive will handle more RPM just fine. I need to find a 22p bravo 1 prop now. The motor should be good to 6500+ no problem. Seems like the boat should be faster than it is and thats what I am trying to figure out. Any one got any idea what a 1991 24 ft elimator fun deck (or Daytona) weighs? The 58 mph last weekend was with 5 people and 50 gallons of gas so we were very loaded down, and plug 58 into the prop calc at 15% slip and it confirms its only spinnng 4500 rpm.



I am thinking if I can get the RPM up some the motor will start breathing better and make more power and hopefully pick up some MPH.
going down in prop size will get you up on plane faster an more rpm but I don't think your mph will go up you will just rev out faster I would talk to Joel at Bronson hill propeller he is a good guy he can answer all your questions
 

·
Diesel Pimp
Joined
·
1,256 Posts
Thanks for all the feed back. Sounds like the drive will handle more RPM just fine. I need to find a 22p bravo 1 prop now. The motor should be good to 6500+ no problem. Seems like the boat should be faster than it is and thats what I am trying to figure out. Any one got any idea what a 1991 24 ft elimator fun deck (or Daytona) weighs? The 58 mph last weekend was with 5 people and 50 gallons of gas so we were very loaded down, and plug 58 into the prop calc at 15% slip and it confirms its only spinnng 4500 rpm.



I am thinking if I can get the RPM up some the motor will start breathing better and make more power and hopefully pick up some MPH.
What are the specs on your motor? If it isn't in it's powerband yet you might get some speed from the higher RPM.

It may be a stupid question, but are you trimming it out?
 

·
Registered
Joined
·
390 Posts
Discussion Starter #8 (Edited)
What are the specs on your motor? If it isn't in it's powerband yet you might get some speed from the higher RPM.

It may be a stupid question, but are you trimming it out?
The motor probably falls off the torque curve around 6K so at 4500 its just starting to run. Its a 523 inch, flat top, merlin iron heads flowed at 370cc intakes, roller cam (.653/.660 lift and 248/254 @0.050), Vr Jr intake, Holley HP-1000 carb, timing at 40 degrees (High Altitude), IMCO thru hull exhaust.


Yes I had it trimmed up and flyin high, probably breaking water at the last couple feet. Rooster tail was about 3-5 ft up.
 

·
Registered
Joined
·
317 Posts
The motor probably falls off the torque curve around 6K so at 4500 its just starting to run. Its a 523 inch, flat top, merlin iron heads flowed at 370cc intakes, roller cam (.653/.660 lift and 248/254 @0.050), Vr Jr intake, Holley HP-1000 carb, timing at 40 degrees (High Altitude), IMCO thru hull exhaust.


Yes I had it trimmed up and flyin high, probably breaking water at the last couple feet. Rooster tail was about 3-5 ft up.
If the motor runs perfect in all ways I say play with props go on offshore only for sale adds under props ther is a few guys the have tons of differnt size merc props cheap be sure to write down rpm wot an speed from gps. With each prop u try
 

·
Registered
Joined
·
390 Posts
Discussion Starter #10
Kind of what I was thinking. I ordered a 22p Bravo 1 the other day, so now I just need to get out there and give it a try.
 

·
Registered
Joined
·
60 Posts
9100

We run our black hawk leg on a tunnel hull, KT, with a 5lt and 1.65 gears, spin them up to 8800
And on our other boat, we have a Bravo one, with a yammaha prop, with 1.5 gears and spin the bravo one up to 9200 we have,
For a gear change its very precise, you need to space it and what not, it you dont get the spacing right, your box can fly apart.
 

·
Registered
Joined
·
390 Posts
Discussion Starter #12
^^^ Wow that is very impressive!

I ran the boat last weekend with the 22p prop instead of the 24p and did not really pick up any speed, maybe a couple mph, but the bottom and mid range sure is better. I still need to fix the tach wires so don't know the exact RPM but using a online calculator I am guessing its 5000. None the less it sounds like the drive has room to go another 1000 rpm or so.
 

·
Registered
Joined
·
59 Posts
Your Bravo drive won't be happy for long if you turn it much over 5k rpm. Need to get accurate rpm readings though.

I'm fighting the same density altitude problems at the butte; have a locker full of props but really can only use a couple of them. Too bad I didn't see this before you bought a 22p B1....have one you could have tried out. You might also want to try a 21p Rev4, depending on how your deck boat likes bow lift.
 

·
Registered
Joined
·
390 Posts
Discussion Starter #14
I don't know if the boat could defentatly use more bow lift or not. I typically keep it trimmed all the way down and run pretty slow as the wife and daughter are more comfortable not bouncing around so much. With the thin air the tunnels do not start to really lift here until 50-55 mph and that is with a bunch (maybe to much) trim. If you have a 21p Rev 4 that is availble I would certainly love to try it. I think our next trip down there will be the weekend of the 27th. Even if you don't have a Rev 4 if your down there that weekend we should hook up.
 

·
Registered
Joined
·
59 Posts
not sure if ill be there on the 27th but probably. You're welcome to try that prop; is what I've been running lately.
 
1 - 15 of 15 Posts
Top