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TOPIC: 496 Bravo 3

496 Bravo 3 20 May 2009 00:30 #1

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Has anybody out there put a MPI 496 Bravo 3 in a 2858 bayliner before. Iam just wondering how much better fuel economy I can expect to get by replacing my 454 bravo 2 and what kind of performance I can expect to gain as this boat is tail heavy anyway.As this boat sit I am getting about 20 gph at cruise speed.

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496 Bravo 3 20 May 2009 01:39 #2

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No direct knowlege but it takes fuel to make HP and you aren't going to be all that different at same speeds between either power package. Now more power will let you go faster but you will pay (gph for that privlege).

Change in drive from B2 to B3 will probably help the situation to get more prop without extra diameter (diameter is drag).

Carb to FI at cruise speed shouldn't make all that much difference if the carb is properly tuned. FI will start better and be better at slow speeds for fuel use but when you start making speed and carb tune is right fuel air ratio is fuel air ratio regardless if you have a carb or FI dumping fuel into the engine.

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496 Bravo 3 20 May 2009 01:42 #3

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I'm doubting that tossing in a stroked 496 is gonna help your gas mileage any... but it'll definitely put a smile on your face. :)

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496 Bravo 3 20 May 2009 02:53 #4

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Agreed with SS. If anything, if this is really eating at you, do it in stages. Convert to a B3 first (its a bolt-on, supposedly) and measure improvements. Save up and convert to a 496 later.

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496 Bravo 3 20 May 2009 04:10 #5

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I am currently installing a volvo 8.1 fuel injected with a dual prop outdrive in my 2859. The volvo dealer told me that I could expect about 20% better fuel economy with this set up over the old 454, but I will believe that when I see it.

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Current boat - 1992 Wellcraft Eclipse 216.
Short list of wanted boats - Bayliner 2252, 3388, Advantage 22 Citation.
Past boats - Bayliner 3270, 2859, 2359, 1950 X 3, 2550, Wellcraft Nova III, Advantage 20.5 Classic BR.

496 Bravo 3 20 May 2009 11:04 #6

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One of my dock mates dropped a 496 into his 2859. He did not mention precentages but he said it was an improvemnt over his carbed & tired 454.

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Port: Sassafras River Georgetown, MD Bayliner 2000 2855 7.4

http://www.chart.state.md.us/video/video.php?feed=0601b947006500d40050fa36c4235c0a

496 Bravo 3 20 May 2009 13:15 #7

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Thanks for all the replys guys still havent made up my mind yet but it sounds like i will go for it go for it and i will let you know how she goes

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496 Bravo 3 20 May 2009 15:26 #8

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OOBOY!!...helping to spend another sailors money is more fun than a fart in a space suit!!....get the 8.1mpi....totally more fun than the tired ole brick sitting in your boat...:eek:


:arr arrr

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496 Bravo 3 20 May 2009 15:36 #9

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seapuppy;297971 wrote: OOBOY!!...helping to spend another sailors money is more fun than a fart in a space suit!!....get the 8.1mpi....totally more fun than the tired ole brick sitting in your boat...:eek:
:arr arrr


I'm with seapuppy here. "Fuel economy and 496" is an oxymoron. Unless your old 454 is clapped out, the ROI (payback) is in the never column.
On the other hand it will certainly perform better with the FI package.

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496 Bravo 3 20 May 2009 16:20 #10

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I seem to have read that there's no real efficiency gain going to a BIII from a BII. Merc claimed better efficiency only at top speed (Volvo claims better efficiency throughout the Duoprop's rpm range). Low speed handling should improve with the counter-rotating props.

Blade area, not necessarily diameter, will increase drag - but it will also more efficiently transmit engine power to the water, thus diminishing prop slippage, and that's your real concern on this kind of a boat/powerplant package.

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496 Bravo 3 20 May 2009 19:04 #11

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shiphead;297741 wrote: Has anybody out there put a MPI 496 Bravo 3 in a 2858 bayliner before. Iam just wondering how much better fuel economy I can expect to get by replacing my 454 bravo 2 and what kind of performance I can expect to gain as this boat is tail heavy anyway.As this boat sit I am getting about 20 gph at cruise speed.

A guy in my city installed a 375hp Volvo DP in his 2850 Contessa.
It didn't do very well with the previous 350 single prop, but with this new engine/drive will now hit 52 mph. He claims 4mpg, but I'd go with 2.
The speed was read from a gps.

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496 Bravo 3 19 Jun 2009 06:27 #12

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Just wanted to let you guys know that I went ahead and droped in a new 496 with a volvo duo prop unbelievable difference .traveled 50 miles with 4 fishermen and enough supplies for 4 days of fishing. 170 liters of fuel cruising at 30mph. Wot was 39mph . The boat handles the speed fine. had a hard time getting out of the hole before and needed full trim tabs all day long to stay up on step now she leaps out of the hole and no tabs afters shes up. Made a whole new boat out of my 2858 .very happy camper now thanks for all your help

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496 Bravo 3 19 Jun 2009 07:05 #13

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375hp = 52mph in a 2850 Contessa? If that were the case I'd be swapping this winter!

Just like in cars, a newer motor with FI over carb can lead to some solid # improvements. Also, a motor which is not running full out all the time to stay on plane like the 350 4bbl in my 2850 will get a lot better economy.

Do the Bravo's share the same transom mount as the Alpha 1 (thus being a direct swap with no cutting for the cobra) or do I have to make some changes?

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496 Bravo 3 19 Jun 2009 14:26 #14

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ishiboo;311928 wrote: 375hp = 52mph in a 2850 Contessa? If that were the case I'd be swapping this winter!

Just like in cars, a newer motor with FI over carb can lead to some solid # improvements. Also, a motor which is not running full out all the time to stay on plane like the 350 4bbl in my 2850 will get a lot better economy.

Do the Bravo's share the same transom mount as the Alpha 1 (thus being a direct swap with no cutting for the cobra) or do I have to make some changes?


Yup, you read that correct.

52mph!

I'd expect that you would need a new transom plate for the installation; don't know if the hole needs to be enlarged.

But, yes, an astounding improvement in performance for a 2850!

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496 Bravo 3 19 Jun 2009 15:17 #15

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shiphead;311926 wrote: Just wanted to let you guys know that I went ahead and droped in a new 496 with a volvo duo prop unbelievable


What did that end up costing you after all was said and done? The MPI alone probably made a huge difference.

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496 Bravo 3 19 Jun 2009 15:30 #16

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I repowered a 28 from a Bravo 2 454 carb to a Bravo Three 7.4 injected. I wore out the first engine at 1600hrs the Bravo 2 performed as new the whole time, great drive, fairly inexpensive props. I bought the carb version for ease of repair which as quoted before I got to do.
The fuel injected Bravo 3 was an improvement but not as dramatic as expected and in unexpected ways. Fuel consuption and top speed improved some at top end 1/2 gallon per hour and 2kn to 40 kn from 38kn. The midrange fuel consumption remained about the same but the mininum speed to hold plane dropped from between 17kn to 19kn depending on chop to 16kn. The extra bite with the drive tucked in provided enough lift to hold plane slower. The big surprise was slow speed fuel economy which went from 1.4 kn mpg to over 4knmg. This effectivly gave me over 400kn miles of range if I needed at 6-7kn. The injected motor also started quicker and idled much smoother. The big draw back to the Bravo three is the cost of props. Going to the 8.1 means more midrange torque and a better ability to hold plane at slow speeds, to me top speed is not important, it's usable speed and fuel economy. Since the 8.1 weighs the same as the 454 and the internal fiction is probably about the same you might actually see some midrange improvement. If you run your boat in the ocean and rough water the extra torque will be a great asset in big waves. Hey it's only money whats to lose? If it were me and the current engine and drive needed replacing I'd go with 8.1. If the Drive is still in good shape I'd probably stay with the Bravo 2 for the cheaper props.

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496 Bravo 3 19 Jun 2009 17:11 #17

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Scary;312072 wrote: Going to the 8.1 means more midrange torque and a better ability to hold plane at slow speeds, to me top speed is not important, it's usable speed and fuel economy. If you run your boat in the ocean and rough water the extra torque will be a great asset in big waves. Hey it's only money whats to lose?


I noticed the same thing going from an alpha drive to a BIII; the ability to plane at lower speeds and the fact that it was easy to MAINTAIN those speeds. The 16mph minimum planing speed sounds similar to what I've observed.
Like you, I think that top speed is of little importance; only good for showing off and stressing your engine unnecessarily.

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2007 Discovery 246
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