Bravo 3's to Bravo XR's
02-07-2009 | 07:38 PM
#12
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Joined: Mar 2008
Posts: 315
Likes: 2
From: Kissimmee, Florida
Carder
tried the set up today, 70 deg. flat water b1 1.50:1 26" bravo 1 four blades, spinning out, no toe in or toe out on drives, set up exactly straight on
3400 rpm 43 mph drives @1.5 tabs @ 4.5
4800 rpm 64 mph drives @ 5 tabs @1 (wide open throttle)
4000 rpm 54.5 mph drives @ 3 tabs @ 3.5
boat came on plane just slightly longer than b3, with rpm maxing out @ 4000 when coming on plane. probably should have 24's B1 four blades to get the rpm up to 5000/5100. Had to trim out too far to get to 4800. boat seamed to run smoother with less vibration with the b1's. driving around dock was fine. Also, boat ran best with very little trim on drives, 1.5 to 2.5. I'm thinking of trying my b1 lowers on my b3 uppers which should give me a 1.81:1 ratio and maybe trying my 28 b1's from the formula. Also, I'm interested in trying 2" imco shorties with maximus 5 blades. My recent previous best speed with the b3 setup and all the crap I've put in the boat is 59 mph, so I did get 5 mph in the setup change.
tried the set up today, 70 deg. flat water b1 1.50:1 26" bravo 1 four blades, spinning out, no toe in or toe out on drives, set up exactly straight on
3400 rpm 43 mph drives @1.5 tabs @ 4.5
4800 rpm 64 mph drives @ 5 tabs @1 (wide open throttle)
4000 rpm 54.5 mph drives @ 3 tabs @ 3.5
boat came on plane just slightly longer than b3, with rpm maxing out @ 4000 when coming on plane. probably should have 24's B1 four blades to get the rpm up to 5000/5100. Had to trim out too far to get to 4800. boat seamed to run smoother with less vibration with the b1's. driving around dock was fine. Also, boat ran best with very little trim on drives, 1.5 to 2.5. I'm thinking of trying my b1 lowers on my b3 uppers which should give me a 1.81:1 ratio and maybe trying my 28 b1's from the formula. Also, I'm interested in trying 2" imco shorties with maximus 5 blades. My recent previous best speed with the b3 setup and all the crap I've put in the boat is 59 mph, so I did get 5 mph in the setup change.
02-08-2009 | 12:02 PM
#13
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Joined: May 2007
Posts: 424
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From: Linwood, Saginaw Bay
38,
That is impressive, especially on a virgin first run.
I agree with you that you haven't got the best prop/drive ratio set-up yet, but I like your thinking on the other combos.
Please keep me posted, I am living vicariously through your boating. We have about 16 in of ice on Lake Huron, and am looking at several thousand ice fisherman where boats should be.
Carder
That is impressive, especially on a virgin first run.
I agree with you that you haven't got the best prop/drive ratio set-up yet, but I like your thinking on the other combos.
Please keep me posted, I am living vicariously through your boating. We have about 16 in of ice on Lake Huron, and am looking at several thousand ice fisherman where boats should be.
Carder
02-08-2009 | 05:06 PM
#14
Platinum Member
Joined: May 2005
Posts: 2,124
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From: Magnolia, Texas
We have done several of these swaps. The main thing to consider is that manufactures usually put the Bravo III drives about 2" deeper into the water. (lower X dimension)
To perform a true "apples to apples" swap, you would need to bolt on an XR w/ a 2" shorty lower.
I first did this on my 257 Carrera party cat in 1998. It went from 68MPH to 74MPH. However, the best part was then adding more HP and achieving 102MPH...
To perform a true "apples to apples" swap, you would need to bolt on an XR w/ a 2" shorty lower.
I first did this on my 257 Carrera party cat in 1998. It went from 68MPH to 74MPH. However, the best part was then adding more HP and achieving 102MPH...
02-09-2009 | 12:36 PM
#16
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Joined: Mar 2008
Posts: 315
Likes: 2
From: Kissimmee, Florida
Boatman22
I do agree the x-dim on the b3 and b1 are the same. What I think billet was saying is that boat manufacturers set up the b3 deeper in the water. I've always thought that Bajas (and the 3 Formula's I've owned) have always had conservative x-dims. I read that Reggie raised the x-dims on some of the newer Fajas and gained some top speed while not loosing any other performance standards, he did add external hydraulic steering to compensate though. I think he set up the 38 Express cruiser with a conservative x-dim partly because of the cruiser aspect of the cockpit floor. My engine hatch (also cockpit floor) almost sits on top of the 496 plastic cover, so while the boat may benefit from a higher x-dim, Fountain didn't want to sacrifice other design aspects of the boat. My thought on the 2" shorty is that it would be real easy to add spacers if the x-dim ends up too high.
I do agree the x-dim on the b3 and b1 are the same. What I think billet was saying is that boat manufacturers set up the b3 deeper in the water. I've always thought that Bajas (and the 3 Formula's I've owned) have always had conservative x-dims. I read that Reggie raised the x-dims on some of the newer Fajas and gained some top speed while not loosing any other performance standards, he did add external hydraulic steering to compensate though. I think he set up the 38 Express cruiser with a conservative x-dim partly because of the cruiser aspect of the cockpit floor. My engine hatch (also cockpit floor) almost sits on top of the 496 plastic cover, so while the boat may benefit from a higher x-dim, Fountain didn't want to sacrifice other design aspects of the boat. My thought on the 2" shorty is that it would be real easy to add spacers if the x-dim ends up too high.
