Do you really want me to comment.  This could get heated.

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1.  I have both, 330 hp 350 and 450+hp 454...well over 200 hrs on junk parts...
      SBC parts are everywhere, even 7-11 
2.  open loop vs closed loop? Your pickup- closed loop. SBC or BBC with a heat exchanger- closed loop.
     My junkyard crap- open loop, one with logs and snails, one with headers, temps at speed-125*-135* adjusted gate valve once, on each boat.....DONE
     Lower water temps produce MORE HP than 160*/180*/210*...or whatever

You can have as much horsepower as your wallet will afford...SBC, BBC, BBF, BBO, Etc...

Dan'l

Well Ive been doing a TON of research(the small block 400 was just one idea ive seen and the closed loop cooling system totaly makes sence to me..) and Ive seen alot of different boats, setups, opinions, watched vidoes and read alot of forum posts from all over the country and canada. I just dont see many guys running the SB..

In short, most small block engines just do not have the torque handling strength that is ideal for a jet pump. The Chevy 400 has to be one of the worst Marine engines on the planet, cylinder wall and gasket integrity makes it an outright "wrong" block choice IMHO. You would be much better off (IMHO) building a stroked 350 (383). I have built a few with pretty impressive result, but will still get it's ass handed to it by a properly built, but still stock 454.


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I know a small block can be built up for cheaper than a BB and the power: weight ratio with a badass pump setup, to me, would run laps around a BB. I love the BBC(I built one myself in my pickup[468]) so im already biased to the BB but the numbers just make sence to run a SB...

Except the small block simply cannot generate the torque up top like a Rat, they need to spin a gazillion RPM which causes the impeller to be cut down to a dinner plate and the performance of the pump take the big poo poo.

Now the closed loop cooling system...why not just run the same setup as a pickup truck? It'll keep all the sand out of the water ports, theres no fuckin with the goddamn water valves(no half turn this, half turn that BS), and you can have the motor run at a consistent temp, just like a car. Id run a super cool tstat maybe in the 160 degree range.

Except (and this is your argument) you just eliminated any weight savings by going small block, the equipment necessary to go to closed cooling weighs in at about 150 #, you will need all the pulleys and water pump on the front of the engine, the heat exchanger, which weighs about 80 pounds full of water, all the related stat housings, filler neck and large hoses, plus you will still have to regulate the flow on the heat exchanger... It is done all the time, just built one from scratch about four months ago...

Might put a couple 1/8" in the face of the stat to get a little more flow for those long poker runs...if you still wanted to run wet stacks, still use the tap off the pump housing, run your plumbing accordingly, but place a gate between the housing and headers.

Don't need holes in the stats...

Also with a closed loop system the chance over over pressuring the water system by having a valvhe open too far or the other being closed too much and blowing a head gasket reduces drastically..

This is true, but when they overheat, it is way more dramatic. Not to mention dangerous (200°F+ water under 15 pounds of pressure)...

I dont actually own a boat myself but Im really interested in seeing what other people have to say about these theories...great numbers/less weight and worry free/consistant cooling...doesn't seem like rocket science lol I look forward to the comments

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Other than the lack luster torque curve of a small block, I would say you are on to something.... BTW, Aluminum whitewater fishing boats have been doing this for decades, typically with a Kodiak or a Hamilton jet unit. They work killer and you can run a heater core like from a school bus under the dash to stay nice and toasty while fishing in the winter time when it's 40°F outside and raining.   


Talking about these badboys..




GT

In short, most small block engines just do not have the torque handling strength that is ideal for a jet pump. The Chevy 400 has to be one of the worst Marine engines on the planet, cylinder wall and gasket integrity makes it an outright "wrong" block choice IMHO. You would be much better off (IMHO) building a stroked 350 (383). I have built a few with pretty impressive result, but will still get it's ass handed to it by a properly built, but still stock 454.


.
Except the small block simply cannot generate the torque up top like a Rat, they need to spin a gazillion RPM which causes the impeller to be cut down to a dinner plate and the performance of the pump take the big poo poo.

Except (and this is your argument) you just eliminated any weight savings by going small block, the equipment necessary to go to closed cooling weighs in at about 150 #, you will need all the pulleys and water pump on the front of the engine, the heat exchanger, which weighs about 80 pounds full of water, all the related stat housings, filler neck and large hoses, plus you will still have to regulate the flow on the heat exchanger... It is done all the time, just built one from scratch about four months ago...

Don't need holes in the stats...

This is true, but when they overheat, it is way more dramatic. Not to mention dangerous (200°F+ water under 15 pounds of pressure)...

Other than the lack luster torque curve of a small block, I would say you are on to something.... BTW, Aluminum whitewater fishing boats have been doing this for decades, typically with a Kodiak or a Hamilton jet unit. They work killer and you can run a heater core like from a school bus under the dash to stay nice and toasty while fishing in the winter time when it's 40°F outside and raining.   


Talking about these badboys..




GT

one other thing gt, why not run a SS impeller that could handle the higher rpms?? How bout using a stuffer in a modified bowl with a nozel insert..use Bernoulli's rule..?

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The impeller can be made out of titanium, that wont change the fact that the pump curve will look a lot like a chewed up toothpick...

Nozzle inserts just make the same amount of water go faster, only works on a very light hull, you will not be able to really tell the difference using the tried and true Ass-O-Nometer...

JMHO

GT

ass o meter...awesome!! Im gonna have to research a little bit more on that pump curvey thing your speaking of..thanks dude

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Ah I see said the blind man..

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Everyone that has commented has made valid points for sure, my experience with bbc to sbc is not as extreme as everyone else although I do run a bbc open loop cooling in my 21 open bow and it has plenty of power and runs great no issues nothing. Kroggy just bought a 21 open bow shock wave with the 6.2L sbc fuel injected closed loop, and that motor has shocked me every time I get into or drive his boat. the sbc has plenty of power to push that heavy open bow around the river at a comfy 55 - 57 mph while getting great mpg I think the *** fills up every 4 trips as oppose to me filling up every trip. If your wanting to build a sick ass hp boat I'd definetly go with a bbc if your wanting good power and don't wanna spend as much and have a bad ass motor that will get great mpg then maybe sbc is the way to go. Just my .02 and again I'm no big engine guru just a fellow jet boat guy sharing my knowledge.

SRC



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Is this 6.2 a fuel injected LS motor?  That's a whole different animal IMO.  Traditional BBC v.s. SBC to me comes down to bigger boat, bigger motor when talking jet  boats.  GT explained why pretty well.  I would say the cost difference between  the 2 builds is minimal at best, not enough to choose one over the other, so why short change your ride.  Why pull the nuts out of a small block to get it to do the same things a mild build BBC can do for years with out trying hard, and only maintenance is oil changes.  Fuel consumption again isn't  really part of the  equation, maybe a couple gallons a weekend, 10.00 dollars?
Change the drive to say an IO then all this changes.

Now if you want to build a 6.2 MPFI closed loop motor that would be a cool motor to build and put in a day cruiser, maybe even throw a turbo on it just because.  Someday that will be a build I'd like to do.