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?

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.

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.

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.

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?

Have you considered a trawler?

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

Put a small block in it and tell us how it works out . Then when you go to sell it you can let us know how that works out for you as well . :bong:

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.

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.

DING DING DING! And you gain 5' of cockpit space!:coolcowboy:

One of these http://www.mshs.com/engine_sales/fpt_nef.htm a Arneson drive and Enjoy your boat!

I originally intended to put outboards on it and get the bigger and more useful cockpit, but with the swim step and the notch, the engines would be about 4 feet behind the transom! We would have had to extend the hull, and while that's not a HUGE problem, its another $10-15K.

I think the comments that a BBC and a SBC will burn pretty much the same fuel to generate the same HP is probably correct. And the weight difference is not that much. And the torque of a BBC is dramatically more.

There are some single engine versions of my boat, and they go nearly as fast as mine: a single 525 goes about 50 knots, mine goes about 55 knots.

I do lust for a diesel engine, but it still seems like the cost is so high (an additional $30K) that I will never see a savings.

Sounds like a BBC is the way to go.

For small blocks, check out the numbers on a 383 stroker (5.7L .030 over, 400 crank). Pretty impressive, reliable power.

Go Twin Small Blocks
 

I used to have a 35 Fountain with twin 500EFi's and now have a 27' Hallett with twin MerCruiser Scorpions which are 377" small blocks with Bravos. The speeds and Power settings are almost identical to what they were on the Fountain but the fuel burn is 50% of what the big blocks used. Just cruising and idleing in and out of the harbors my average fuel burn has been 12.5 to 14 gph and that includes some running at 4000 rpm and a lot of running at 3000-3200 rpm. They seem to be very efficient. Since your boat already is set up with twins it would be an easy swap, you would have the safety margin of a second engine to bring you in, I think that is important on the ocean. Your big blocks are certainly very saleable, so the conversion shouldn't cost too much.

All things considered, the single Diesel is your best choice, but also the most expensive. If you really love the boat and plan to keep it for ever, go DIESEL.

You might want to look into selling your boat and buy one that has the power that you like. That may be the most economical choice.

Oh- for sure you can make good power. And they are light especially with aluminum parts and if you have the bones - an aluminum block.


By the time you buy new exhaust (you'll find none for SB's used) buy steel cranks and tough recip assemblies, good heads, and a good roller cam, all the marinizing pieces sea, pump etc. (good luck finding a single belt kit for a small block that will work) all the accessories are no cheaper than a big block

You need to walk a much finer line between idle quality and power output (head size and cam selection are more critiical for good manners) with a SB just because more cubes make for better manners all around.

After you are all done you'll have spent about what you'd spend on a big block.

My 406 in my little boat rocks balls, but it was no cheaper and a bunch harder to do than a bbc.

Uncle Dave

i agree. if you put twin small blocks that would be a descent approach. reducing your power to one small block. not even sure you would get out of the hole with a 32'.

We can cut you a Smokin deal on a Red 625 with a warranty. Ask Uncle Dave how his single 7-10 is on fuel. PM me if you want

Amazing.



UD

Ding! Another winner. The torque curve on the 625 will probably not kill the the drive, either. (Plus, you take out another 200 pounds as compared to a big block.

one small block and that size of boat I dont know. I would think twin small blocks, or one single 502 or something. One small block is going to suck fuel too. I understand your thoughts and Im not going to get into the whole if you dont have money your in the wrong sport, like some other tards say. I mean anybody can get into any sport. Just because you have a go fast doesnt mean it has to go 80 and cost 500 bucks a weekend to run. Different strokes for different folks. But I do have to agree you are going to kill resale, unless you keep it for a long time and at that time a 30 year old boat, it dont matter what it has it isnt worth much

get a different boat.....