If you can buy a new GM crate engine with 525hp and 519lbs of TQ or whatever,, Whate would be a reason not to buy a long block or short block and add the mercruiser 525 intake/ injectoion system-or not even do that? You can find em for 8-12,000 pending what form you want. Why is Merc so high $$ is there that much a diff. to pay double.

Different torque curves between street and marine use. Street you shift through gears... marine not so much. I have seen a few high end car engine builders build some high end engines that last a few hours in the go fast world due to major setup differences... I have also see a few guys buy automotive crate engines and never get on plane due to the torque curve being so far off. Just my 2 cents...

Buy the marine one there is a difference brass inserts etc etc double the engine life also

There have been so many threads on this subject in past years and good inteDligent answers to this question with explanations that they would fill a good size phonebook. Do your research and answer finding. Just type in "crate engines" in the forum search lookup and let the floodgates open.

Best Regards,
Ray @ Raylar

I'd consider a GM crate shortblock myself. Like a 454ho. If one needs to replace a shortblock, or start from scratch, its not too bad a deal. I think ive seen them for 3800.00.

When you factor in the cost to properly rebuild a shortblock, with full machine work, pistons, rod recon, balancing, etc, sometimes you're not far off from a new shortblock, with all new parts, standard bore, etc. Not too mention the fact you order one, and it's at your door in a week, where as sometimes waiting on a machine shop can take several weeks or more.

The money saved on just buying the GM shortblock assembly vs the whole crate engine, leaves money left over to get a better set of heads than GM offers, and go with inconel valves. Then spec a nice cam, and its not hard to have a 500-550HP engine.

The majority of engines mercruiser uses, are using a GM shortblock, except for the higher end merc racing stuff.

I have a buddy who had a old Formula with a pair of 454's. He rebuilt them, had issues, fiddled and fiddled and just had problems. Finally got aggravated, ordered up a pair of GM 454HO crate engines, all his troubles ended. I believe those engines are still in that boat today, with MANY MANY hours, and still going strong after about 12 years.

I bought a new crate ZZ572 2006. Had some head job done, new inconel valves, springs etc.
Stock cam. New holley 1000cfm carb, mech fuel marine pump and all marine stuff.
Dyno 630hp at 5600rpm. Had it in a HEAVY 28 Pantera Race. 80mph in rough water.
Was a great engine.

Biggest difference would be cam shaft. Way more duration possible on street w/mutli speed transmissions as Raylar already stated and way more over lap as well. Both kill torque which is king in our single speed, 100% loaded water toys.
I get it on the O/B side all the time too where someone says, lets stand a Hyabusa engine on end and see what it will do. I can save them the time and money.
Stop at a light w/your Busa, at the base of a long, steep incline, seat your girlfriend on the back, jam it in 6th gear now let out the clutch and see how that works for you.
I love the stories of the car motor guys that build the killer motors for their hot rod I/O's and lose 5 MPH's
Not to say that a crate motor w/a different cam (maybe rockers?) and freeze plugs might not be good bang for the buck though.