airjunky

iTrader: (2)

Ill be that guy and ask why they dont put more big blocks in new wave of surf boats. 1 motor hauling 9k endlessly across the lake at 50% throttle and 3-4000 rpm. Maybe a good profit margin on those supercharged ls motors and stroked vortecs

CDShack

I think on smaller boats they're fine, even smaller twins. But on big, heavy boats as mentioned, it's just simpler to make torque with a traditional big block, and they will do it all day. I like the LS, but it's the same reasoning they aren't used in 18-wheelers. A "big" block is just a lot of metal (translate strength) to take a butt-whipping and keep on going. My plain jane 454s make 500ft/lbs. at 2500 (that's were the dyno readout started) and was about flat all the way across.
I was told by an offshore engine builder once that "boat motors are built to haul 10,000 pounds up a mountain all day at 5500 rpm". Not that small blocks can't, but BB are just a better, more reliable and cheap option I think.

SB

iTrader: (1)

Fuk'm. Most big block boats go under 70 anyway...and these are usually the one's that ask...so, if you either beat them or stay with them, when they ask, the answer is "It's a 307 olds rocket motor with a Harley carb." They either get embarrased believe you) or they look twice and walk away (they think you are fuk'd in the head) or they stare at you, pause, and then laugh knowing you are sandbagging.

Swamplizard

Good stuff. My beast is 42ft and 15,000 so not a candidate for SBC - just curious what the board would say. Happy Holidays all.

Uncle Dave

Ilmor also claims that they had to do significant work to the oiling system to get the longevity they needed which runs counter to all the little guy builders that claim LS's are bulletproof.

Corey- can you share your dyno sheet and parts list?
You were running lighting headers right?
I remember something from earlier this year.

Thanks.

UD

sprink58

This discussion sort of reminds me of my Sea Ray days when I had a 40' EC with twin 3208 CATs. The Gas version of this boat had twin 454's and wouldn't even stay close in open water....and used almost double the fuel. It's all about the torque.

Then one day a guy showed up in a 34 EC with twin LSA's and blew all my "Small Blocks can't build torque" theories to hell. !! LOL

My rule of thumb has become that around 30' and 8000 lbs is the tipping point for SBC's...beyond that you go to BBCs up until you get to 40' and 14,000 lbs of displacement...then you look seriously at diesels.

I have been on 27' and 30' Formulas with both: Twin BBCs and Twin SBCs. In that length and weight category I feel that the SBCs (Vortec Roller and beyond) yield a more balanced package overall. Beyond that size boat...it's a "Fool's Errand" to try to match the bang for the buck torque that a BBC brings to the table.

My mechanical Engineering background dictates a lot of my thinking on this. Big torque demands the durability provided by the mass of iron in the blocks and sectional modulus of the cranks available in the BBC architecture. I will say though...as available LS motors find there way into our marine applications, I think the Bang for the Buck advantage enjoyed for decades by the BBC is beginning to tip in favor of the LS technology.

It's a great debate...and having said that...it's time for another Single Malt !! LOL

tommymonza

Sprink what are the specs on your SBCs and what kind of coin did you have into them minus exhaust ?

What kind of speeds you getting out of your Formula and did you change your x -dimension?

flashgordon

yes, besides enjoying the go fast boats, I have also had several sea rays, and yes I had years ago the 39 ec sea ray with 454 was under powered. in fact the shop that did my 547;s , also put a pair of 547 in a 39 sea ray ec. but I think bottom line is weight, as stated by sprink58, I think he stated the ''line'' 30 ft..8000lbs. I could not imagine a pair of small blocks trying to push my 10,000 scarab. also someone mentioned a small block is 500 lbs lighter,,??? not sure on that one.

corey331

Parts List:

Stock LS2 Block, bored .030
Callies 4" 4340 Crank
Callies 6.125" 4340 Compstar Rods with ARP 2000 bolts
Wiseco forged pistons -8cc dish
Stock 317 truck heads with PRC (Texas Speed) stage 2.5 CNC Port, opened to 70cc's. Makes 10.5:1 Compression
Bob Madera cam, 243/250, .621/.613 112ls
Its a carb motor running Daytona Sensors Smart Spark LS ignition

To address the oiling issue, which is that the motors can actually pump too much oil over long hard runs, and can drain the pan before gravity can put the oil back down, I had a custom 12 quart oil pan made by Kevko Pans. I am also running a 29"x3" oil cooler with a built in thermostat and dual remote oil filters. All in all I have just over a 14 quart capacity.

I am running Lightning headers. I fought reversion a big part of last year, so I completely dried up the exhaust.

I tried to find my dyno sheets last night, but seem to have misplaced them. I'll have to get a new printout from my engine builder. I will however be dynoing it again here pretty soon. I am changing over to closed cooling and want to tweek the ignition a little. I feel like there is more power in the motor with a little more tuning.

Here is a pic of the motor right after I set it in the boat and before I dried up the exhaust.



Here is a quick video of it idling at the dock my buddy took the first time I had it out last summer. I am in love with the way a cammed up LS sounds!!!

https://www.youtube.com/watch?v=MtwwjdHgAr8

corey331

my stock motor was a 310hp carb'd 454. It had iron exhaust and an iron intake. Fully dressed with accessories, it weighed right around 1100lbs.

When I dropped the ALL ALUMINUM LS2 into my boat, we did it at my buddies farm on his truck scales. As you can see here, the LS2 only weighed 480lbs.




I then went home and weighed the headers, oil cooler and alternator. They weighed in at almost 70lbs. The Aeromotive Fuel System weighs almost 10 pounds. Making a dressed weight of 560lbs. 1100lbs minus 560lbs equals a weight savings of 540lbs.

So yeah, you can save over 500lbs. I will agree that I had about the heaviest BBC there is in the boat. But I will still think that you would save 300-400lbs over a hp500 or similar motor.