These huge NA engines make the power they do because of the rpm they turn and their compression. Get the rpm down to where its usable in an IO and you may not have the same peak power, but you'd have freight train torque and the same reliability as any other engine. Then the challenge would be keeping an outdrive together.

Please tell us about the high HP marine engines you have built and how many hours they lasted.

Not sure if the "price prohibited" excuse holds water [so to speak] when your dealing with fella's who are dropping WELL over a million on a boat, in some cases SEVERAL boats in that price range, I doubt the extra cost of a Sonny or Fulton motor would make THAT big of a difference, just my thoughts.

Sonny has built lots of marine engines, as well as "street" motors, I too, have wondered why more people dont run a big inch/EFI Sonny Leonard Motor?

I agree that a 16:1 compression "Chemi" running over an inch of lift is probably not gonna be real low maintainance. But, that same motor with a 9:1 piston, smaller cam, steel rods, traditional valve train and EFI could be made pretty livable.

I have never priced a pair of Merc 1350's, but, I doubt they are cheap, and I am not sure what the recommended maintainance intervals are on them either.

That Sonny's 1325 hp engine with EFI & dry sump and then customized for your boat setup is going to be in the 70k range. However, it doesn't include the drive, transom assembly, bellhousing, coupler, etc. Adding a set of Arnesons, M8s, or equal isn't cheap. I could not find anything regarding warranty on Sonny's site.

The Merc 1350 at 200k includes the complete package (engine, trans, transom, M8 drive), and is warranted for boat use, with 'normal' marine maintenance. Maintenance & warraty is by Merc dealers.

So, while Sonny builds one heck of a package, isn't compaing his 61k engine package to the 200k Merc engine/drive package apples to oranges?

A thing to notice. All comparisons in this thread is between Merc and Sonny. I for one don't care much for the way too expensive merc's at all, but that's me.
The interesting comparison is between 1200-1300 hp from a Sonny big cube n/a motor and the custom stuff from YPM, Sterling, TCM, Chief, Potter ect. A blown hydraulic roller motor pushing the same power, will last a long time and be less expensive. The price thing is not about affordabillity, but about sense. A 1200-1300 hp motor from the before mentioned prolly won't cost 70-75k+. Just as an example, why pay say a 125k for a Sonny's 1005 n/a pushing 1300-1500 hp, when fx. Sterling and others can build 1300-1500 hp for less than 75k. the Sonny won't be more reliable than the others.
All my examples are of course if it was marinized Sonny's engines, not the drag engines.

1st, love the comment about NOTHING special about a marine engine...really ??? so that means I could take my take my "small" Sonny's 565 that ran in my Top sportsman car and be fine...who would have known !!!! damn learn something new everyday !!!...now back to the question, Sonny would have no problem setting one of his monsters up for marine use on 89 octane...I just think with all the torque he's making tuff finding a drive to hold up without spending $$$$$$$ but I guess after spending what he gets for his engines...and I know 1st hand(not so say he does not knows whats up by no means as he build some of the baddest drag race engines on the planet) that may not be a deal to some....

Just curious, how much does a Teague, Chief, Pfaff, 1300 EFI cost and what drive would they use ? do they run on 91 octane ?

Are you high? or are you just being sarcastic?

High performance marine engines are CERTAINLY different than drag engines which are different than circle track engines which are different from police car engines and minivan engines.

The assembly clearances on a motor is different depending on its application. The selection of parts and materials and coatings is different depending on its application. The oiling and cooling systems are different (not just the bolt-on stuff, but also the size of the passageways, the route of the fluid, etc) depending on the application. The cam selections have to take different things into consideration. the spring selections have to endure different rates of heat cycling. The steady-state combustion pressures and EGTs have different ranges depending on the application.

Sure, a 330hp 454 is basically the same engine you had in your 3/4 ton Chevy truck in 1978 but the Merc 1075SCi is a LOT different motor than a 1200hp BBC blower motor for a bracket racer.

As stated above, I hope you were just kidding.
MC

A Sonny's engine in marine tune with a cam, lifters and valvesprings that can live for 150 hours and a 10 to 1 compression would make about 1.3 hp per cubic inch. That's 1040 hp for a 800 cu. in. For a whole lot less you can build a 540 and put a supercharger on it. His larger engines and his 5.3 hemi heads probably can't be used in an endurance or marine application. Does the 5.3 hemi head even have water cooling or are they solid billet? The ports and valves are designed for a 2000 rpm idle and a 9000 rpm redline. How do you make them work at 1000-6000? Can the lifters and rocker arms live for hours of high rpm running when they were designed for running for 6 seconds at a time? I wouldn't want to be the crash test dummy for this project.

Perhaps more to the marine world would be this offering. Note the "Endurance Application" 925HP at 6500 rpm. Getting closer. Detune to 6K rpm limit and heads/valves that can take unleaded 91 fuel consistently.
http://www.sonnysracingengines.com/s...-racing-engine