Interesting even if you are not a boater

[callbay]

I put this here as it is not about boat engine lubrication.

http://www.boattest.com/review/formula/3095_353-fastech

Just wondered what your thoughts were about a new small block Chevy but a 454 cid vs the normal 496 or 502 cid big block Chevy in a boat sterndrive engine.

Seems like an amazing new engine putting out 570 hp for a small block.

I looked up the sterndrive engine only weights for comparison to the new 454 smallblock 570 HP Ilmore.

The 454 Ilmore weighs 830 lbs.

A 430Hp Mercury Marine engine 502 cid weighs 1,122 or 292 more or 584 more for 2 engines.

A 565 HP Mercruiser Racing engine (largest with no supercharger) weighs 1201 or 371 more than 70 Ilmor or 742 more for 2 of them.

Would there be a lot of torque difference for the 48 less cid for the 454 vs a 502?


Also I don't remember the relationship between bore and stroke as to how it effects torque and HP??

Your thoughts please.

 

[Linctex]

Just thinking about all the gas those things burn gives me a headache......

I had an Olds 455 jet boat (1972 Avenger) with a 20 gallon tank that lasted about an hour, tops.

 

[ZZman]

Bigger bore means bigger valves. That can mean more peak power. Add a short stoke and you have high rpm and horsepower.

Longer stroke is more torque.

 

[maxdustington]

I am shocked they are still using BBCs in boats. They have been obsolete on the roads for 20 years.
No fuel economy targets to meet on a boat I guess.

 

[Johnny2Bad]

The SB GM Corporate motors easily handle the overbore (which isn't much to begin with over the stock 350 4" bore, and Chev sold many a 400 small block in the 70's that has the same bore as the big blocks). The blocks need to be clearanced to allow the larger stroke crankshaft but that too has been done a million times.

Aside from the weight savings of the iron castings, the newer SBs are all aluminum (block and heads), which shaves a few more pounds.

Mercury Marine is very invested in SB performance, in fact GM sells high performance (off-highway use) smallblock cylinder head castings that were engineered by Mercury and are cast in a Mercury foundry.

Similarly Mercury's conventional iron SB and BB blocks were always cast with a higher quality alloy that what GM sold for passenger car or truck use. So even the conventional marine engines are high performance parts.

As for BBCs in boats, well, they use motors that are much larger than that ... caterpillar diesels, for example, and dual motors is far from state-of-the-art ... triples and quads are the norm at the very top echelons, and we are still talking speedboats, not tugboats.

 

[jhellwig]

If it is one of the merlin or world block sbc 454 it isn't going to last long in a boat. if it is one of the ls 454 engines it might have a chance.

 

[BrocLuno]

Boats are all about TQ at some rated RPM. The prop or the jet is calibrated to the torque curve and has to push against skin friction, hull shape (wave making) and load (the physics of moving a weight up a ramp) as the hull transitions from displacement to planing ...

Fuel economy comes with reductions in all those params. But boats are mostly people haulers that carry amenities to make people happy. An ultra-light aluminum hull with not padding, no beer cooler, no porta-potty, no Navy top or sun shade, etc - will make for a poor people abode and bad ride (usually). Just like an older Caddy, mass means comfort. Fuel is sacrificed to move that comfort around.

The OP's idea is a good one. Modern SBC mated to an efficient stern drive will reduce mass. If the displacement of the engine can be made workable (Eagle block ...) and reliable, it would be a step in the right direction. Vee drive might be lighter and more efficient, but they scare folks who have to sit adjacent to spinning shafts and cranky gear boxes ...

The ideal hull shape depends on the water surface. Smaller lake w/o long fetch area means small waves so flatter hull with less skin friction will work. Flatter hull means easier to plane. Won't work in the Pacific where we have thousands of miles of fetch area to make waves. Need Vee hull for ride and handling in bigger waves. Vee hulls do not really like Vee drives, so stern drives rule. Conditions dictate minimum displacement and shape. All goes up from there as amenities are added ...

 

[Johnny2Bad]

Originally Posted By: jhellwig
If it is one of the merlin or world block sbc 454 it isn't going to last long in a boat. if it is one of the ls 454 engines it might have a chance.


They don't use automotive engines in boats. Everything is different (although the parts do bolt up) from the alloys used to the fuel and cooling systems. There is no such thing as a two-bolt mains marine block, for example. Before aftermarket sbc's were available the racers used to try and find marine blocks if they could (mostly, they couldn't).

Mercury supplied the ZR-1 engines to GM in the C4 Corvette. They currently offer two LS-based (smallblock) crate engines for automotive use, a 7.0L 750 HP conventional fuel injected motor and a 9.0L 1350 HP forced induction (twin turbo) model. DOHC, 4 vales per cylinder. This stuff is old hat to them.

 

[BrocLuno]

Thing is an average sedan takes about 15 HP to move at 60 MPH at sea level on radial tires (no A/C, windows up) A modest boat will take 15 gallons per hour (diesel, with more BTU/gallon) to move at 50 MPH. That's 3+ miles per gallon and considered good. To get up to 6 MPG in a boat, you really have to be on your toes design and load wise ... There is a reason we abandoned canals for highways ...

 

[dareo]

Wow, cool boat. Too bad its like 300k and a gallon a minute of fuel at speed. I really like how well they labeled all the hoses and stuff.

So to go use this thing you probably are looking at a lot of fuel to drive it to a lake, and 149 gallons of fuel in the boat itself. Seems like it could be around a $500 a day just at the gas station for this hobby.

 

[irv]

Originally Posted By: dareo
Wow, cool boat. Too bad its like 300k and a gallon a minute of fuel at speed. I really like how well they labeled all the hoses and stuff.

So to go use this thing you probably are looking at a lot of fuel to drive it to a lake, and 149 gallons of fuel in the boat itself. Seems like it could be around a $500 a day just at the gas station for this hobby.


The bigger the boat/engine the more money. My bud's previous boat could suck it back quickly, and using premium only only added to the costs.
It was a fun ride while it lasted but he sold it and decided to buy this one instead.

 

[gfh77665]

Lots of fishermen / sportsmen friends here where I live. When the discussion comes up, I tell them the secret to prosperity is NOT owning a boat!

 

[supton]

I wonder how long a 454 cubic inch SBC is going to last. I mean, that's a fair amount larger than original. Although I guess aftermarket blocks could be using 4 bolt mains with cross bolts and who knows what.

Does the rod/stroke ratio come into play? Seems to me that it'd be hard on bores. But perhaps this application isn't about max life.

 

[ls1mike]

Originally Posted By: supton
I wonder how long a 454 cubic inch SBC is going to last. I mean, that's a fair amount larger than original. Although I guess aftermarket blocks could be using 4 bolt mains with cross bolts and who knows what.

Does the rod/stroke ratio come into play? Seems to me that it'd be hard on bores. But perhaps this application isn't about max life.


You talking old 454 or LSX 454?

 

[jhellwig]

Originally Posted By: Johnny2Bad
Originally Posted By: jhellwig
If it is one of the merlin or world block sbc 454 it isn't going to last long in a boat. if it is one of the ls 454 engines it might have a chance.


They don't use automotive engines in boats. Everything is different (although the parts do bolt up) from the alloys used to the fuel and cooling systems. There is no such thing as a two-bolt mains marine block, for example. Before aftermarket sbc's were available the racers used to try and find marine blocks if they could (mostly, they couldn't).

Mercury supplied the ZR-1 engines to GM in the C4 Corvette. They currently offer two LS-based (smallblock) crate engines for automotive use, a 7.0L 750 HP conventional fuel injected motor and a 9.0L 1350 HP forced induction (twin turbo) model. DOHC, 4 vales per cylinder. This stuff is old hat to them.


Maybe that marine one is a different beast altogether. I just figured it was based on the world or merlin blocks that had to be lengthened and even then had siamese bores to make that displacement. About the only common parts with any other sbc were the front and back end. Well suited for a drag car but not ideal for a constant power application.

Sorry I meant motown not merlin.

 

[SilverSnake]

Originally Posted By: Linctex
Just thinking about all the gas those things burn gives me a headache...…


Not only a headache but a pain in the wallet. My final boat was a 35' Silverton with twin Crusader V-8's and V-Drives. At 30 gallons per hour at cruise it did not take long to empty the 176 gallon fuel tank.

 

[supton]

Originally Posted By: ls1mike
Originally Posted By: supton
I wonder how long a 454 cubic inch SBC is going to last. I mean, that's a fair amount larger than original. Although I guess aftermarket blocks could be using 4 bolt mains with cross bolts and who knows what.

Does the rod/stroke ratio come into play? Seems to me that it'd be hard on bores. But perhaps this application isn't about max life.


You talking old 454 or LSX 454?


Old small block based. If they are basing on the LS series then I could see it lasting many hours (potentially) as that is a much different block with a lot more in it.

I mean, this is a boat application, not some street/strip machine. Sitting at some high load for hours at a time is not (usually) the place for highly stressed engines used well outside their design envelope. I'm not saying it's going to grenade after a few hours, just that longevity is usually inversely proportional to power output for a given engine family.

 

[NYEngineer]

That 35 footer is sweet. Those are LS based engines in that thing.

I was an engine builder/machinist in a big shop on the South shore of Long Island in 1984-87. We did mostly stroker Chevy big blocks and untold hundreds of small blocks in house and even had a dyno. Dream job for a kid that loved engines like I did. Back then, the blocks were the SAME blocks that were in cars. We were a certified rebuilder for Mercruiser and the parts that came in to be rebuilt for them were exactly the same as automotive parts down to the casting numbers. Many of the Mercruiser parts came in GM bags with Mercruiser part numbers stuck on them. The bigger stroker big blocks, like the 540 used a Chevy Bow Tie block back then. There wasn't parts availability like today.

I've been out of boats for years but I do know of a few really cool marine engines. Mercruiser for example makes a couple of clean sheet big blocks with dual overhead cams in the 565 cubic inch range. Supposed to go WAY longer between refreshes than a BBC.
There's also an outboard with a V8 LS standing on end that looks and sounds amazing. Wish I had cash for a couple of those.

My last boat was a 20 foot Allison Craft with a 225 Johnson. I was trying to squeeze 100+ out of it. Only got it to 94. I guess it was fast enough. No one in my area could even hope to keep up with it.