Difference Between Boat and Car Engines
 

All I have a mildly built 355 chevy that has a marine cam and aluminum heads, full roller rockers, cam, and timing set. Could this be used in a boat???? I have heard mixed opinions. this is a brand new freshly built engine all bearings are new , new pistons, edelbrock heads, comp cam's extreme marine cam. I was originally going to put this in a car but sold the car. Anyway, I found a boat I think it would be fun to put in. Just wondering if this would work? It has never been run.

Work, yes---but it will need more marinizing. For safety reasons, it will need a marine carb, marine distributor, alternator. Chances are you will need aftermarket exhuast also.

Been my experience that marine motors besides having all the safety and brass stuff need to produce a lot of torque and carry it throughout the power band.
Someone once told me a car motor in a boat and the boat would not get out of it's own way and a marine engine in a car the car would beat itself to death. :Whatever:
I just drive 'em (both..one sometimes better than the other):D

brass freeze plugs too...

I'd anodize the aluminum heads unless they are marine heads already done. Also what's the compression ratio? They usually go lower on marine engines to reduce the chance of detonation. Exhaust valves are usually changed to Inconel, or if on a budget stainless steel.

Michael

Usually, piston to wall, ring, bearing clearances are different on a marine engine because its running sustained high RPM's

The stress on a marine engine is like driving your automobile in first gear all the time. That's why marinizers start with the heavy duty truck engine and go from there. Good things to have are 4-bolt main bearings, a forged steel crank, a cam grind that works in the RPM that benefits marine use, forged pistons, brass freeze plugs, heavy duty valve train, etc.

If you are cooling the engine with salt water, a minimum of aluminum is better. A passenger car engine will have a very short life as a marine engine.

Engine specifics
 

Compression ration should be 9 to 1, The motor is a long block out of a truck 99 chevy Vortec. It is a two bolt main but has been balanced and new rod bolts etc. the aluminum heads are off the shelf Edelbrock Performer heads old style with the same size 64cc chambers that the stock vortec's have. I used stock gaskets so I'm guessing that 9 to 1 would be pretty darn close. The heads most likely do not have anodizeing they are stock , and have whatever valvetrain comes stock in them. They are good to like .550 lift. I have steel roller rockers, comp cam's marine cam with operating range of 1000 to 5000. I have no carb, ignition, or exhaust for it. I was thinking of swapping this into an application that currently has an old Merc 260 hp 350.

I'm not sure about the freeze plugs. I will have to check on that. Also Running in fresh water only.

If that's the case, then why can't they develop a transmission just like a car that can lower the stress on the engine?

Nothing will lower the stress. You could lower rpms, but that increases the strain. It's better to rev them than to lug them. Merc did make a trans to give a low gear for holeshot, not many bought it.

I forgot to mention that marine engines use head gaskets made of corrosion resistant materials, too. Marine engines often (but not always) have forged components, especially the crank and rods.

Michael

That would be like shifting into high gear at 30mph and trying to go up a steep hill. A boat hull has a lot more resistance than 4 spinning wheels on a car.

paint it blue and put a mercury sticker on it and you will have magically turned it into a marine engine.

"Marine engines have an extra .001"-.003" bore clearance because of high load operation and cold water to the block. A cold block with hot pistons is what dictates the need for extra marine clearance."

http://racingsecrets.com/article_racing-10.html

People overlook this very important fact all the time. They are usually pushing a rope back to the dock!

I agree with all of the above. Since the early 1980's I have seen lots of boat guys who had a machine shop that is used to building great car engines fail when they were in stalled in an offshore boat. Piston to cylinder wall clearance, piston ring end gap, valve guide clearances all has something to do with "thermal expansion". The weight of oil you use and keeping it cool is important as well.

Finding a good precision machine shop that builds a truly decent marine engine is hard enough itself. Even many of these guys and their machine shops who are used to building great car engines for the past 20+ years....they have a lot of pride and you can't tell them anything because they think they know it all because of their sucesses with car/street engines. Think twice before you take your engine(s) to a machine shop used to building car engines...street, drag strip, oval......no matter how good they are. It is usually hard for them to grasp the marine offshore engine thing.

Also, cam differences. The only thing I could think of that would even be close to a marine cam would be a tame hi-perf street legal cam. You have to consider the engine's RPM operating range and the application when used for a marine engine.

The best way I have heard a marine engine being described is: A marine engine is like a semi pulling a full load of heavy cargo up a mountain. The torque has to be there and you have to keep everything cool at the same time.

Sorry about the soap box presentation. Have fun.

Can anyone (specifically anyone who works/worked for either company or has FIRST hand knowledge- not I know someone who knows someone) answer the question of what is the difference between the short block that GM performance sells -ZZ502 - and the shortblock that come with the "marine engines" from 1800runsnew and the likes. We are talking about only the shortblocks (not heads, cams, etc). You can buy a GM ZZ502 shortblock for approx $ 4400 I think and the 1800runsnew total engine is about $ 5400. Is someone taking apart these shortblocks, changing/checking clearances, balancing and reassembly, and then charge only an extra $1000 for the entire motor?? Point is I have heard that the 415 horse 502 comes from a plain GM performance shortblock (forged piston, steel crank, 7/16 rods etc.) and the 500 hp was disassembled and changed/checked, balanced and reassembed. Sorry for the long post.

Thank All
 

Very interesting perspectives. I know for a fact the guy that machined my engine is very very very PROUD. He got Really , Really pissed off when I asked him if I should plasti gauge the bearing clearance's etc. He said no! Thats what you paid us for. ( I plasti gauged anyway :cool-smiley-026:).Anyway, that said, It sounds like I would be better off not to put this engine in a boat, I know the crank and rods are not forged, I know the piston clearance and rod bearing, ring gap and etc is to manufacturer specs. My measurements showed the bearing clearances were on the tight side of the range and so were the ring gaps. I would assume those spec's are for automotive use. Sounds like I would be pushing my luck. I have no idea on the 502 question.:ernaehrung004:

I don't think anybody asked what you were going to put this in. If it were going in a light weight 16 foot jet boat it would probably work fine with the right impellor. We are on OSO so I assume it is going in something bigger.

I have done some experimenting with this I bought new a boat with a 350 mag blew it up and tore it down I found no 4bolt main cast pistons and crank nothing different than a 78 chevy truck engine. I even ran my 350 mag cam in my 78 chevy truck to see what it would do and how it would react I found not much different than the cam it came stock with. I even tore apart the starters one from the truck and one that said marine stamped on it and found no difference they were exactly the same. The water pump on the front of the marine motor went bad had a gm pt# matched up to a 68 corvette. I built a marine small block without using marine parts but with marine clearances except for carb, fuel pump, and alt and ign and it has performed flawlessly for over 700hours. So go figure.

The alt and starter dist, etc. have spark protection and should be coast guard approved.

When GM was making the old style small block 350 and 305 for passenger cars and trucks, how many do you think they made a year. As a percentage, how many went into boats? I think this is where you will find the answer to the great debate.

I spoke to a high volume marine engine manufacturer recently, and one of their engines is based off the ZZ502. They just get a GM crate engine, replace the valves with Inconel, put it back together, and dress it. That's it. He's says they have had no problems.

This is not to take away from what people have mentioned here. The higher the performance, and load, the more changes you should be making, including changing clearances, etc.

Michael

:D:D:D

Didn't eliminator take the 572 motor from gm, change the cam and put it in a boat. Thought i read in magazine that they did and it worked good. Of course i don't think they said how long it worked good.