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Old 10-08-2017, 11:45 AM   #1
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Default New 357s in my 3200 SCR

I replaced my old-style merc 5.7L 260HP engines with a pair of Mercruiser 357 Magnum Bravo 4V, they are rated at 325HP each.

My boat: 1995 3200 SCR, with Bravo IIs.
Half tank gas, water tank empty, holding tank quarter full.
Just me an my mechanic on the test run.
Nearly flat water, wind less than 2 knots.

Planes quicker, I didn't time it but will get some timings soon.
Pushed throttles wide open, engines are rated 4400-4800 rpm, mine got right to 4800. Didn't really trim it that much, was doing 37 mph.

Very happy with them so if anyone is ever considering what options these are pretty decent for the price.

Some links on line:

https://www.mercurymarine.com/en/us/...specifications
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Old 10-08-2017, 11:48 AM   #2
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In my boat, took these at night though, so they aren't that clear.
But....

20171003_190910.jpg

20171003_190902.jpg
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Old 10-08-2017, 12:19 PM   #3
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Very nice. According to the video the engine has a mechanical fuel pump so it a pre-Vortec rebuild. Last year I dropped in a new 5.7 Vortec but used the old bolt on stuff and rebuilt the Weber carb. She is rated at 320 HP. Definitely can feel the power increase over the old 260 HP.

Enjoy
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Old 10-10-2017, 02:29 AM   #4
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Even though it does have a mechanical fuel pump, it is indeed a Vortec engine, has 8-bolt intake, heads. Mercruiser drills the block to accept the mechanical fuel pump. It would be a challenge to get 325hp from a 4-bbl carb, 356 cu in without the engine being a vortec design.
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Old 10-10-2017, 11:41 AM   #5
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Quote:
Originally Posted by jamanati View Post
Even though it does have a mechanical fuel pump, it is indeed a Vortec engine, has 8-bolt intake, heads. Mercruiser drills the block to accept the mechanical fuel pump. It would be a challenge to get 325hp from a 4-bbl carb, 356 cu in without the engine being a vortec design.
Strongly disagree that it would be a challenge to build a high HP non-Vortec 350. This was done all the time in the 70's and 80's and engine builders are still doing it.
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Old 10-11-2017, 02:15 PM   #6
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Strongly disagree that it would be a challenge to build a high HP non-Vortec 350. This was done all the time in the 70's and 80's and engine builders are still doing it.
Our 1967 Firebird 400ci is doing over 500hp on a 650 cfm Holley and pump gas.

Nascar 350's do 900hp on a 4 barrel carb (fuel injected now) with a restrictor plate.



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Old 10-11-2017, 04:09 PM   #7
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Not sure I would use a NASCAR engine for comparison as its a much different animal. But the L-48 version put out 295HP and the LT-1 that was used in the 1970 corvette put out 370HP but that had 11:1 compression. The Vortec heads help creating high HP using low octane.
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Old 10-11-2017, 04:17 PM   #8
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Not sure I would use a NASCAR engine for comparison as its a much different animal. But the L-48 version put out 295HP and the LT-1 that was used in the 1970 corvette put out 370HP but that had 11:1 compression. The Vortec heads help creating high HP using low octane.
Yea, my first comment was really the comparison. Just was thinking about how much you really can squeeze out of the same displacement

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Old 10-11-2017, 11:19 PM   #9
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True, can build out a custom marine engine out of 350 cu in to crank out more than 300 HP. Would need ported/specific heads, custom valves, aggressive cam, roller/lifter set, timing tuning, carb tuning, etc. Not saying it isn't possible, but it's a challenge to do it with standard, easily available marine parts from your local marine shop. Plus it gives 3 year warranty. I'm happy with them is just my point.
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Old 10-12-2017, 01:15 AM   #10
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True, can build out a custom marine engine out of 350 cu in to crank out more than 300 HP. Would need ported/specific heads, custom valves, aggressive cam, roller/lifter set, timing tuning, carb tuning, etc. Not saying it isn't possible, but it's a challenge to do it with standard, easily available marine parts from your local marine shop. Plus it gives 3 year warranty. I'm happy with them is just my point.

I hear you and I would be very happy with the engines you picked, I was just saying a pre Vortec engine is capable of high HP from the factory back in the day and it was done without being that aggressive of a build. Today's engines can do it by advancing the timing much further since they incorporate a knock sensor to protect them.
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