HardCore Racing Motors???

Any positive/negatave feed back about these motors being sold in Summit? The 540 750 HP kinda has my eye.

Car motors have different piston/wall and valvestem/guide clearances. The cams aren't the same,valve materials(especially the exhaust) aren't as good,the oiling pressure side and drainback sides are not usually modified as a boat should have. And most of all,read the fine print,it usually states"not for boat use".This is because they know that boats require the abovementioned differences.Boats run at cooler tempratures,higher power levels and rpm for longer periods of time, I have just touched on the basics,consult a REPUTABLE BOAT ENGINE builder for more details.

Hammer if these are Hardcore (as in Bill Mitchell World Products) automotive crate motors do not use them in a marine application. They will not be warrantied and will likely have issues. (Good motors but not for marine use). We went through this a couple years ago with World and they built us a bunch of marine 540's (not the auto version Summit and others sell). We had several problems even with these special 540 and 509 engines. We stopped handling them due to that.
My understanding is that Bob Teague now has some marine 540's from World with some changes from the ones we had that are lasting pretty well. I haven't seen the specs on them though. Likely differences are in the heads, valves used, cams, distributor, compression ratio, rod type, etc. Be prepared to pay more than the automotive crate motor though. Even though they look similar they are not the same. Don't let the Summit guys tell you they are.

All valid points...thanks.

I learned the lesson the hardway and my mitchell motor did not last long.

DEL51:
I learned the lesson the hardway and my mitchell motor did not last long. What more or less happened to it? Was it one of there "Marine" Motors?

Hammer, I had a LS7 and had them build a blower motor out of it. They were the king in the magazines back then.But they were into normally aspirated engines. I shipped the Long block and had vendors such as littlefield send the right stuff, pre paid to them.The engine lasted about 2 hours and I had a horizontal lifter bar break.The lifter trashed the lifter bore and packed the sump with scrap metal. I had it "fixed" in chicago by r&r engineering.Then, another situation, This time it was ripped of parts from an employee that liked my jesel belt drive.Bottom line , it was two seasons of do nothing cause of the motor and about 12 grand lost. On a little 454-460 and finally a 468 chev.I took the engine to a guy in omro wisconsin and he really fixed the problem, said it was in the valve train geometry and port matched the merlin heads.He couldn't understand why they installed such a cam for boat performance.Afterwards, With 3 225lbs guys in the front seat of the sanger she read 97mph @ 10 lbls boost spinning an A impeller @6250 rpm.I have since moved to a new boat and engine but I know that you can sometimes pay for lack of experience
And I have learned alot.

I forgot to add that I had the engine dynoed at mitchells and it made 746 hp at 7200 rpm. 690 ft lbs of torque at 4200. This was with 2 1050 doms and 10 Lbs of boost. It turned my b impeller to 6050 rpm.After the change I had to go to an A.

Thanks for the info...I know the biggest word in a Motor Build is Research...and then even more Research. I know is difficult finding someone (shop) that can back up all there talk. Everyone has there own thoughts on how something should be done... I know of one place that said "don't ever question me". I turned and walked out of his shop...Funny, some of these Motor Builders get insulted if you ask to many questions.