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Small block instead of big blocks?

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Old 05-26-2011, 11:48 AM
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Default Small block instead of big blocks?

I am sick of paying hundreds of dollars for fuel for a weekend. Its fun, just not that fun.

So I've pulled both big blocks out of my boat, filled in the transom, tweaked the stringers, and I'm going to put in a single. Getting 1250 lbs or so out of the ass end (15% of the total weight of the boat) will certainly reduce fuel burn.

But all of us who ever owned hot rods know that big blocks consume an awful lot more fuel than small blocks.

So I'm considering putting a single, stroked, small block instead of using one of the 454s I pulled out.

Typically, I cruise the islands off Southern California. The Pacific Ocean sets the speed, not the throttle. Most of the time the ocean sets the speed at 20 to 25 knots, where I use 200 to 250 HP, with full tabs down, drives all the way in. When its smooth, the same fuel flow but tabs up and drives out a bit gives me 35 knots. Its really never smooth enough in the ocean to go faster than 35 (well, maybe once every other year). So 250 HP is all I need with two big blocks in the ass end. With 1250 lbs less aft, I'll certainly use much less power, probably 150 to 200 hp for these speeds.

A boat with similar weight, the Skipjack 262, works great with a single 200HP diesel, running these same speeds.

Any comments?
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Old 05-26-2011, 12:00 PM
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I know money is always the main concern but you could put in two of these but they are worth more than the boat itself http://www.cmdmarine.com/Products/Re...82062_6_08.pdf

If you were going to the trouble of converting to a single why would you not look for a used 250hp - 330hp Cummins B series engine? You would get the cruise you wanted and burn little to no fuel.

I would bet if you looked around you could fine a pair of 220hp or 250hp B's, they are 4 cyl and would drop into where the big blocks were. You could bolt these to a Bravo with no problem don't even go down the diesel torque issue as you won't prop it big enough to get the cruise speeds you want plus.

I know it's costly but would probably make you happier in the look run.
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Old 05-26-2011, 01:59 PM
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a SB putting out the same power as a big block will burn about the same amount of fuel.

Personally, I'd have opted for twin small blocks. I don't do all that bad with twin small blocks.
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Old 05-26-2011, 02:07 PM
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You'll hate it. It will be a dog out of the hole (if it even gets on plane) and you won't save much gas. It will also kill the resale.

Have you considered lobbying your socialist state legislatures. They seem to think $8 a gallon would be a good thing for their god.........I mean mother earth.
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Old 05-26-2011, 02:09 PM
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I've heard it many times here before. "If you're worried about gas money, you may have the wrong hobby". I do however understand your frustration, I just bought a twin big block boat last year and am selling my single BB boat. How long will you have to run the single SB before your investment pays off?
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Old 05-26-2011, 02:16 PM
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Have you considered a trawler?
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Old 05-26-2011, 02:27 PM
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Quote:
Originally Posted by carcrash View Post
I am sick of paying hundreds of dollars for fuel for a weekend. Its fun, just not that fun.

So I've pulled both big blocks out of my boat, filled in the transom, tweaked the stringers, and I'm going to put in a single. Getting 1250 lbs or so out of the ass end (15% of the total weight of the boat) will certainly reduce fuel burn.

But all of us who ever owned hot rods know that big blocks consume an awful lot more fuel than small blocks.

So I'm considering putting a single, stroked, small block instead of using one of the 454s I pulled out.

Typically, I cruise the islands off Southern California. The Pacific Ocean sets the speed, not the throttle. Most of the time the ocean sets the speed at 20 to 25 knots, where I use 200 to 250 HP, with full tabs down, drives all the way in. When its smooth, the same fuel flow but tabs up and drives out a bit gives me 35 knots. Its really never smooth enough in the ocean to go faster than 35 (well, maybe once every other year). So 250 HP is all I need with two big blocks in the ass end. With 1250 lbs less aft, I'll certainly use much less power, probably 150 to 200 hp for these speeds.

A boat with similar weight, the Skipjack 262, works great with a single 200HP diesel, running these same speeds.

Any comments?
Tex is correct.

Stick with the BBC.

Actually small block are more expensive per HP to build and marinize. Its also harder to make a small block idle well and be outdrive friendly.

Between a BBC and a SBC either one putting out say 250 HP at speed cruise- they will consume about the same amount of gas.


UD
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Old 05-26-2011, 03:02 PM
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So you want to replace two big blocks with a single small block in a 32 foot sport cruiser?...I don't think that'll work out.
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Old 05-26-2011, 03:12 PM
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Fill the transom, install O/B bracket, put 150 -200 H.P. on. Done !!! And still have twin motors for docking & dependability . "HIGH LIFE"
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Old 05-26-2011, 03:17 PM
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Quote:
Originally Posted by HIGH LIFE View Post
Fill the transom, install O/B bracket, put 150 -200 H.P. on. Done !!! And still have twin motors for docking & dependability . "HIGH LIFE"
Winner, winner, chicken dinner!
Pair of ob's best of both worlds, if you fish a ton though they can be a pain to fish around.
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