Edward R. Cozzi

This post shows you really understand. I applaud you.
Ed

Michael1

You may be waiting a little longer than some people think. I believe this engine had to pass GM's 300 hour durability test, which is at full throttle cycling between peak torque and peak horsepower. I'm not necessarily condoning putting it into a boat stock, but it might do quite well as is.

Michael

handfulz28

I bet it would bounce off the rev limiter until it ran out of gas Fill it up and it would keep going, and going, and going

I think Merc and the marine industry have brainwashed the marine community to be fearful of anything that hasn't been painted by a marine power company. The truth is GM offers a 6.0L and 8.1L that have very little done to them before they have marine accessories bolted on and then go to paint.
Would an LS7 crate motor be "optimized" for marine use? Probably not but all it would need is a cam change. I think it'd be interesting to put a "marinized" LS7 against a 496HO.

Here's another crazy thought applicable to GM crate motors. A buddy's father in law is working on an FAA-certified retro-fit to put "crate" LS2s in Cessnas to replace OEM Lycomings and Continentals. Nothing special done to the power plant, bolt on airplane parts, geared to run around 4000rpm at 75% cruise. These "crate" motors are running over 2000hrs TBO (time between overhaul).
YMMV

MikeyFIN

Whats the diff between a fresh water cooled longblock in marine or auto use?
None most of the time.
As it is an aluminum engine it Has to be fresh water cooled.
So no problem using a crate engine IMO, just a tad more work if you do it yourself.

MikeyFIN

In fact many Merc engines do have only brass freeze plugs changed for marine use and clear black paint instead of flat black...prolly all this even made by GM.
One funny observation was on the 454SS pickups, they had identical engines to the Mercruiser 330...even brass freezeplugs 1990.
And I mean identical even to camgrind and intake cast numbers.

About your dads FAA certification projects, does he have to use a twin plug system?
Some years back there was a FAA certified Chevy all aluminum big block using twin plugs on GM aluminum open chamber heads.
Seeing a LS7 against a 496 HO, well the 496 would certainly meet itīs match but would there be any weight gain with the LS7 as it needs the fresh water cooling system?

Raylar

Here's the old crate engine marine use question again. Obviously the LS7 GM is using in the Corvette is not just any old crate engine. It is hand assembled with a with titanium connecting rods, CNC'd high flow heads, special oil pump, etc.,etc. The problem with this paticular engine for marine use is that it makes its 505HP at almost 7000rpms and its peak torque of only 440 ft/lbs at 5500 rpms which is in my opionion way to high in rpm and low on torque at to high an rpm for good non-racing high performance marine use. At a decent cruise rpm its torque would be down around 300 ft./lbs and it would be lugging. It also has cast hypereutectic pistons for noise reduction. Now take the $17,000 base price and spend another $15,000 or so fully marinizing it and you will start to see why its not going to be the ideal marine high performance motor. We studied all the LS series motors before we started our LSM550 project. What we wanted and knew only this design could give was a closed cooling all aluminum motor that weighs in fully rigged at almost 500lbs less than an aluminum headed big block with closed cooling, is about 4 inches shorter in length, 5 inches shorter in height and will produce 550HP at 5800 rpms and 500 ft/lbs of torque at 4200 rpms. It should price out in the mid to low $20k range complete with stainless headers and hardware when we release it. No crate LS engine would get us there!Remember this engine is 450 cubic inches and there's no replacement for displacement! Its always easy to speculate in "Bench Boating" what would be cool. Its much harder for marine engine developers to deliver what will really work!
We're trying.

Regards,

Ray @ Raylar

handfulz28

Ray, does the crate LS7 come with the variable cam timing? I'm guessing no? Would just a cam change bring the TQ/HP curves more in line to "marine" use? I personally wouldn't use a crate LS7, I'd use the same Raylar is using-the new variable cam timing engine.
I still think the LS-series motors should be the next generation of small block replacements.

MikeyFIN, no twin plug but redundant ECUs plus glass panel graphic display for engine monitoring.

MikeyFIN

Ray howabaout the weight difference compared to a open cooled bigblock?

And Michael yes I thought also about the camchange.
Them LS heads do flow already "like" rectangular ports on bigblocks...

Raylar

LS7 engines do not have any provision for nor can this feature be added for variable cam timing. A cam change would obviously bring the horsepower down and lower the torque curve and peak torque however the lower horsepower of lets say 425hp and probably only about 400 ft/lbs of torque would not make this combination a good big block substitute. The weight of our new engine is still about 400 lbs less than a open cooling big block with iron heads.

Ray @ Raylar

MikeyFIN

Thanks, Well that about answers my question.
But an LS7 I think would with a smaller cam still make more torque than 400.
Depending on the Big block which gets substituted well thats a question too.but thenagain a Bigblock is easy and cheap to make bigger&stronger.