the difference in car VS boat motor ?
 

I want to buy a 540 short block from the same company that builds my drag race mtotrs and build a blower motor . Looking for 650 to 700 hp on pump gas, but am getting conflicting info on this subject !!! Could someone please explain the differences. I am aware of the valves , the cam I assume should be different, the intended rpm range in a boat is obviously different , but what other major difference would there be . I assume all machine work tolerances/clearances would be the same . Thanks for any help ahead of time .

Re: the difference in car VS boat motor ?
 

It seems the tolerances should be set up looser. Cams,Comp.
The "car" guys motors I have seen dont seem to last

Re: the difference in car VS boat motor ?
 

That what I was thinking, a little looser on the ring gaps etc. because of the extended higher rpm usage. But I couldnt think of any other big internal differences . I know oil pan , flame arrestor , valve covers etc. but they are all external items . I just cant come up with anything else major internally . Thats why I am hoping somebody here can give me some help so I dont waste my money if it isnt going to work anyway .

Re: the difference in car VS boat motor ?
 

This his been debated so many times, I have personally argued this with people around my local water. I set my ring gaps according to Total seal recommendations for blower motor, I set my clearances at .0025-.003, and use a 112 LSA or 114 LSA. Salt water applications will need brass in the water jackets for anything aluminum. I run mine in fresh water only, so that has not been a problem. For instance the only difference in a 500 HP and a 502/ 502 is the cam, slight compression difference and intake passages are brass lined. Go for it and you'll save yourself some serious cabbage over the,anything for a boat being twice as expensive, price.

Re: the difference in car VS boat motor ?
 

I dont know...Jeffrey just smoked a brand new zz572..tight clearances. He had some work done to marinize them Dont know what....I am watching his experimant with interest.

Re: the difference in car VS boat motor ?
 

I forgot the thread name - how is is working since he fixed that glitch - still running strong??

Re: the difference in car VS boat motor ?
 

Hopefully people that know more than I do will answer this for you, but I have been told that to convert would require exhaust valves, camshaft, oil pan, head gaskets and changes in tolerances. Also, even aside from those things automotive crate motors are just not put together well enough to survive in a marine application. Even though there are some success stories that make it sound tempting, if enough people respond to this post I think you will find that most people will recommend not using an automotive crate motor. I have paid particular attention to topics like this on the board and talked to alot of people about about it because I have been considering rebuilding/replacing my engines for a while now.

Re: the difference in car VS boat motor ?
 

I have not seen the thread for a few days....Must be good news ! :D

Re: the difference in car VS boat motor ?
 

I have two friends running 502/502's and they are still running fine 4 years later. This does not mean a thing other than what I see. Don't use this as a reference they may work great or they may be lucky I honestly have no clue!

If I did it I would at the very least change cams.

Re: the difference in car VS boat motor ?
 

read this thread, good info to keep in mind with any hi-perf BBC

http://www.offshoreonly.com/forums/s...3&page=1&pp=20

Re: the difference in car VS boat motor ?
 

Man that is a great thread! Wish that discussion was going on a few summers ago when we put the ZZ502 in my Nova. Sure would'a cut down on some of the trial and error stuff, and $ spent.

I have an automotive crate engine in my boat, GM ZZ502/502. And when all is said and done, I'm real happy with it. Very dependable and a strong runner. This is season number three with it. We dropped it in the boat just about "as is" from the crate, with the exception of the head gaskets. I also sent the carb to Nickerson's for marinization and tweaking. And swapped the oil pan off my old 7.4 that was yanked. Also swapped the ignition, starter, alternator, sea/fuel pump, and complete Merc exhaust from the 7.4 to the ZZ. Kept the 110* LSA Cam, and kept the SS exhaust valves. Two seasons ago I took the Merc exhaust off and installed Revolutions. Plus a bigger/better oil cooler.

The engine has performed very well. And I'd do it again. But whether or not you go with an auto type crate motor I think would depend on how hard you intend to run it. I've done a couple of sustained 20-25 mile just about WOT runs with no ill affects. But I think that might be pushing it a bit too hard.

Most of my WOT is limited to just a few minutes at a time {wife screams at me and gives me dirty looks}. Rest of the time we're just cruising around at about 3500-4500 rpms or so.

I think if you're gonna go out and WOT every now and then like we usually do, a crate motor is just fine. But if I was gonna add a blower and or lean on the sticks allot, I'd opt for a properly built marine blower motor.

Disclaimer.....Just my .02......I'm no mechanic, just a dumb azz rambling on about my own experience with a crate motor. Good luck with your decision.

Re: the difference in car VS boat motor ?
 

thanks for all the help this is the latest info I have gotten .

I spoke to a well known marine and car engine builder and they have a complete marine division . They sent me the specs on a 540 non blown car and boat motor . All specs were identical (HP was about 650 on pump gas) as far as torque curve rpm horsepower everthing .I dont have them in front of me or I would list them . Anyway the car engine was 12000 the marine was 16999 both engines turn key. I asked the differences for the extra money and I was told maching and etc. is all the same but the marine motor has inconel exhaust valves , hardened and coated valve seats , fuel pump and system was marinized, 10 quart pan, he included a billet breather and nice valve covers, but he said the biggest difference was the 12 month warranty and that he spends 8 to 10 hours on the dyno getting the fuel curve perfect on the marine engines . I guess my point and or question is , is it really worth it ? I dont run the boat to death but I would like to go a bit faster sometimes . The crate motor with a few upgrades is really seeming to be the way to go , and I can just have the upgrades done when they build the motor .

Re: the difference in car VS boat motor ?
 

J and E piston manufacturer recommends more clearance between the piston and bore.... about .002 more... the thinking is the piston is going to run bigger because of the added heat from more load... and the bore is going to be smaller because of the cooler block than a car. ( If you are running raw cooling).

Re: the difference in car VS boat motor ?
 

That would make sense .

Re: the difference in car VS boat motor ?
 

17K sounds like allot of $. But then 650 turn key hp built right is some pretty serious stuff. That include the exhaust?

Re: the difference in car VS boat motor ?
 

Bert,
So the engine you are looking at is a marine crate motor, not an automotive crate motor?

Re: the difference in car VS boat motor ?
 

Torque curve and where peak torque comes in (RPM) is everything.
Inconel exhaust valves and cylinder bore clearances also very important, as previously mentioned.
Stay away from the automotive stuff.
Regardless of what you build, build for intended application and use.
Don't compromise. You will ultimately pay in the end. :cool:

Re: the difference in car VS boat motor ?
 

About 10K or more under what the larger marine motor builders will do one for and half of what a 600 merc will set you back

Re: the difference in car VS boat motor ?
 

Exhaust not included in the price . I have been looking at and comparing both car crate and complete marine engine's .

Re: the difference in car VS boat motor ?
 

I would like to add a little something to this subject. I am an ASE cert. master machinist and engine builder. I have built both automotive and marine engines for the last 19 years. Before that I worked at a GM dealer. First off, the GM performance parts catalog specifically states that the engines in the catalog are NOT intended for marine applications. That is not to say people haven't used them in a marine application. Some people have had good luck with them and some haven't. I think it depends on how hard they are run.

The above mentioned references to increased piston to bore clearances are right on the money. This is especially important with open cooling systems. Not nearly as much block expansion. There are other differences that most people on here know about and have been listed.
Sorry for the long post. Thanks for listening.

Re: the difference in car VS boat motor ?
 

I have taken apart many Mercury marine engines and I don't see any great diffeences between them and an automotive motor. I mentioned in my first post the main three differences I have known of in disassembling a marine motor. You can't get any better than a Dart BigM or Merlin III block for a start and that is certainly heads and tails better than a Gen 6 502 or a 496 block. Add a couple thousandths more piston to wall clearance to say 6.5 or 7.0, some Inconel exhaust valves which are a whopping $30.00 a piece from Ferrea or Competition products, big deal. Buy a 114 LSA or 112 LSA cam, and you have a great start to a marine motor that will live long. Add brass water jackets to the intake if you plan on going in salt water. Now go on Ebay and start adding all that up and it does not justify the motorspeak price because it's marine. I get tired of hearing how a fellow boater gets it stuck to them because it was a marine motor. Furthermore most marine motors that last a long time a relatively low performance say 500 HP or less. That doesn't strain the parts hard enough to tear it up. 600 HP stresses the rods and crank more, then 700HP even more. When you crank up the power, there is a lot more carb tuning especially, that needs to be done, that seems to be the number one mistake. I haven't torn up a bottom end piece in years, mainly because I use the very best rods I can afford, that is the heart and soul of the motor. The rod bolts take a serious beating.

Re: the difference in car VS boat motor ?
 

Wrist pin clearances. Typically .0007 should be upped to .001 on marine hp. Marine oil pan too.

Re: the difference in car VS boat motor ?
 

Clearances, Play the major rule. I have to add I bought a pair of 454 create motors and put blowers on them .Five years later they still run strong. But what I thought was different ,when I took the intakes off to put the blower intake on and change the cams, the motor came from GM with brass soft plugs and mr43t spark plugs. All I could think is that the boat builders did not buy enough motors from gm and they were selling them over the counter. ???????????

i have a 30 spectre cat put 2-572s changed valve covers and oil pans painted blocks orange and flywheels ,never changed anything inside except little springs on distrubuters to keep timing from bouncing 60 hrs no problems none! totally recomend, these moters are high performance period!

oh the best part ,boat runs 118 mph yea baby! would like to hear from others.just remember to change OIL TO MANUFACTURES RECOMMENDATION 20/50 w racing oil!

Valve guide clearances too.