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Mag 27 X-Dim

Old 02-17-2011, 08:27 AM
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Originally Posted by h2oboater
Marshall just wondering how many inch centers [drive to drive] are you going to use ? 29" to 32" or ??????? A non stepped bottom Mag running 80+, now that's a beautiful thing. Mark
Hey Mark,

They were spread 33 1/2 before and I dont want to change the eng mounts so should stay the same. Hopefully with 550hp a side I see 85mph, we'll see. Hard to imagine now looking at the current state of the boat.

-Marshall
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Old 12-21-2011, 09:51 PM
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Just curious if you have made any progress on locating your Bravo drives. I just finished replacing my transom on my 27 sport and will be running a similar combination, Bravo XRs with 500-550hp SBCs. Mine is currently setup for 32" centers, I am looking for some advice on the x-dimension and some MPH estimates from anyone with a similar combo. Thanks!!
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Old 12-31-2011, 09:30 PM
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Marshal,

I had my boat at lake x and the x dimension was set at 17 3/8" with 31 1/2" centers. I run a sedan with a pair of 420 hp sbc and bravo one's. I run bravo 4 bade props that have been modified. The boat gets up and go's and the exceleration is strong with no cavitation. Im not sure of the wieght differance but I believe you could go a bit higher but for pleasure boating this has been a wise choice for me.
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Old 01-01-2012, 09:37 AM
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I am curious as to what rpm , prpops and speeds you were seeing ?
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Old 01-04-2012, 08:34 AM
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Hey guys,

Sorry, didn't check this thread for a while.

The Mag ran pretty well this summer. My motors (454's) are on 33 1/2 center. Don't have my notes here but I'm almost positive that we went to a 17 1/2" X dim with the bravos after speeking with many riggers including the one doing the new 27. I think the X is right, the boat planes out pretty well at 2600-2800 rpm and can hold a plane around 2400. One thing I found was the boat handles much better with the props turning in. Turning out the stern didnt seem to bite or track or get out of the hole as well. Big difference turning in, I actually bought a set of 1" spacers to try before we turned the props in. I have run 2sets of props. Bravo 1 30" merc lab, and bone stock 32"s. Best #'s are with the 32's, 50mph cruise at 3200 rpm with best 84mph and 5200 rpm. The problem with the topend is the motors were not perfectly matched, not sure why, but one developed boost earlier and would only go to 5000rpm while the other would do 5400. Tearing down to see what the deal is probably a little blow by. Depending on what is found might rebuild the motor and maby go to alum heads. Once I get the motors matched, BBlades thinks we can improve on the slip% and get a few mph maby. Didn't get any pics running this year but have a thread on donzi.net, talk about other boats, mag starfire resto.
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Old 01-04-2012, 06:51 PM
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I'd have to go to the storage facilty to measure the x dimesnion on my 27 Sport.

Twin SBC 500HP ea., Bravo One's running 24" props it was acheiving 87 mph on Lake St. Clair.

Quite a different story when I got her to her new home out West and run on Tahoe at 6250 ft elevation though, maxed out at 3200 rpm and 45 mph! I have gone all the way down to 17" props, now tops out at 5600 rpm and 65 mph, so still hoping to drag a bit more out the old gal.
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Old 01-04-2012, 09:34 PM
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Originally Posted by Joules
I'd have to go to the storage facilty to measure the x dimesnion on my 27 Sport.

Twin SBC 500HP ea., Bravo One's running 24" props it was acheiving 87 mph on Lake St. Clair.

Quite a different story when I got her to her new home out West and run on Tahoe at 6250 ft elevation though, maxed out at 3200 rpm and 45 mph! I have gone all the way down to 17" props, now tops out at 5600 rpm and 65 mph, so still hoping to drag a bit more out the old gal.
Thin air killed that much speed ? Would a fuel injection system be more suitable at that altitude?
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Old 01-05-2012, 10:47 AM
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I want to know how you got to 87mph with 24" pitch props.... 6500 rpm?
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Old 01-05-2012, 09:44 PM
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Thats a good question. I plan on running my Maltese 6500 RPM's with a set of 24 cleavers on my #2's. Would love to know if high 80's is do able.
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Old 01-05-2012, 11:43 PM
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I know this Mag ran 80+, as I DQed it for breaking out of it's class. It was the last race the silver Cup ran Grand Haven. The Short Circuit & Grumpy Old Men Mags were running full out, & both broke out. As the referee I disqualified them both, later we all had a good laugh about the speeds these Mags could run.
Take a look at this post on OSO. Andy, CIG 3 knew this Mag also from the Silver Cup Series.
http://www.offshoreonly.com/forums/m...cuit-sale.html
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