Marine engine vs. car engine?

What if a killer deal on a marine (GM?) 502 came your way? What are the differences, other than exhaust, between it and a car motor?

I can verify it runs and has been treated well.

what year marine engine? I know my father has told me that they often used different heads. They might also need leaded gas

I know that in many cases the crank on a marine engine is not machined to accept a pilot bearing/bushing.

...and some a cammed to rotate backwards.

Probably won't matter on the engine you're talking about, but occasionally conversations come up about the insane power/displacement ratios of jet-ski engines. That is, until someone points out that they've got an effectively infinite supply of 70-degree coolant.

DeadSkunk wrote: ...and some a cammed to rotate backwards.

that would be interesting the first time you put it in 1st and floor it

Interesting thought about the reverse rotation; I have done it with 2 stroke outboards (V8 versions) but never with the 502s that I worked with.

I have to think that an LSX represents a better value in today's world than the 502.

If its from...who...those guys...PCM- it will be your basic torque built 502. There were a number of different 502 crates built over the years- the marines use small port heads, small roller cam for the displacement, but thats all fixable with a call to Edelbrock. I think, although I only have second hand knowledge, that they are nothing unusual, other than manifolds, obviously, and they are generally run by a marine EFI system that uses no O2 sensors. I think its roughly the same efi GM sold on the Ramjet crates, but thats probably not applicable. They quit with reverse rotation a number of years ago. You will have to figure out which generation it is, since GM kept updating the big block. MarkV, GenV, Gen VI to figure out flywheel weights, parts interchange, that sort of stuff. I'd imagine some block casting numbers would tell you that.

My info comes from doing a bit of work for a friend that sells Nautique ski boats. He's installing a marine 502 in his 33 Ford.

It's a 1999 in a performance boat.

I can get numbers off the engine if that will tell me anything. If I can get the numbers can someone tell me what I've got or tell me where to find out?

I don't really have a need for the engine but for the price & depending upon the engine specs I think I could find a use. I have a 280 Z just sitting there, a clapped out S2000 with fender and door damage or I could build a tube framed whatever.

I'd have to find a transmission to fit or just build a hydraulic drive unit.

I can tell you, from sorting out a RamJet 350 at work, GM won't have a reader/scanner for that ECU.

The Ram-Jet is sold through GM parts and comes with a dorky little code reader (pretty much a paperclip and a light) but we have to go through a boat shop to get the ECM really sorted out.

Shawn

I thought most were cammed to spin backwards.

Maybe stick it in a crx and maintain the stock transaxle?

Taiden wrote: I thought most were cammed to spin backwards. Maybe stick it in a crx and maintain the stock transaxle right up until the first launch?

FTFY

Haha no way man. You'd have to maintain the stock transaxle right AFTER every launch.

Usually marine engines are only reverse rotation if it has a mate.

the reverse rotation engines can be made into standard rotation by putting in a regular timing set in place of the gear drive. the reverse rotation engines used a cam gear drive that was just the crank gear meshing directly with the cam gear with no idler gear in between.. the result was that the cam turned in the reverse direction of the crank. they had to do it this way because the distributor needed to keep spinning the same direction in order to spin the oil pump in the proper direction..

put a regular timing chain in there and swap on a regular water pump and exhaust manifolds and you've got yourself a killer street engine that is specifically engineered to hold up to full power WOT blasts for hours on end.

Marine engines are designed to be efficient in a narrower RPM band, since they spend most of their time at one RPM. So cam and ignition tuning is different, and the heads "may" be also.

In reply to mad_machine:
I used to own a formula V that I used for autocrossing. The trans went out and I bought another one, but never thought about the direction of rotation until I tried driving it out of the garage. I had 1 forward gear and 4 reverse gears !

bravenrace wrote: Marine engines are designed to be efficient in a narrower RPM band, since they spend most of their time at one RPM. So cam and ignition tuning is different, and the heads "may" be also.

a lot of the GM crate motors are just repurposed marine engines and as such come with marine cams in them and they do just fine in street car/truck applications.

You'd have to change the cam on a reverse rotating motor. GM had a very ineresting TSB about a marine cam in a Suburban 350 years ago.

I'm on crutches for a few days and found that limits my ability to

1) drive to my friends house

2) get thru the mud to the boat

3) climb in and get the numbers

So I'll have to wait. I'm so used to being able to do anything it never entered my mind that I'd have a problem.

That's the problem with forced sitting around, you have time to think, but you can't DO anything!

He's out of town for a week or so or I'd have him get the numbers for me.

Please dont put this in an S2000. If your going to do that sell the s2000, to me, and get a shell from something else!

The shell is left over from another project and will be junked. It would take a lot of work to make it drivable again so I'm not really thinking I'll use the S, it's just a possibility. There is no suspension under it, nor an interior.

What I expect this version 502 to be means it won't be a really good drag car, because without a lot of work and money it won't be powerful enough. I think it's only about 425 hp. But it's pretty big and heavy for the S2000 body.

I know it will fit in the 280Z but once again that's a lot of weight.

I can't think of anything that it would be ideal for, at least anything I have, it will just end up being a gas drinkin' play toy.

Trans_Maro wrote: Usually marine engines are only reverse rotation if it has a mate.

I need to shed some light on all of this reverse rotation thing....
All marine I/O engines since about 1976 have been normal rotation regardless of how many engines are in the boat. All marine inboard engines have been normal rotation since about 1982. By the time 502s made it into boats, everything was normal rotation. Any reverse prop rotation is accomplished in the transmission or outdrive.

Anyway, its not difficult to make it normal rotation even if it were reverse.

As far as the 502 is concerned, double check the deck height with casting numbers. Many marine 502s were created with tall deck blocks. That only really matters if you don't want to spend bigger bucks on intakes and pistons/rods.

The only real concern with the marine part is that it may give you fits if it ever had saltwater in it. There is never any way to get all the salt out of the pores and salt + glycol coolants = green jello.

curtis73 wrote: The only real concern with the marine part is that it may give you fits if it ever had saltwater in it. There is never any way to get all the salt out of the pores and salt + glycol coolants = green jello.

How is this a problem in a closed-loop cooling system?

This boat has never seen salt water.