Inboards and their Car Engine Counterpart

I was reading a blurb somewhere and the person was saying that almost all inboard engines are manufactured by the big companies (GM, Ford etc) so in theory they are just using standard car engines with slight modifications for the wet enviroment correct?

if thats so would almost any car engine part work on the boat engine? If so how could you tell which engine you have thats the equivelant to the Car Engine?

Im talking parts like alternators, plug wires, spark plugs, carbs, any maintenance stuff etc.

Currently most inboard manuf. are using a GM based engine whether that be a "vortec" or "LSX" style motor. I think Fords were used for 80s and some of the 90s. Most everything can be carried over except with some minor differences for the marine stuff.

You are correct, pretty much every wake/ski/rec boat uses a car based engine with some marine parts. Where the Indmar, Volvo, etc comes in is the company that adapts the engine for marine use. Marine parts are things such as the manifolds, computers, fuel systems, water pumps, etc. What engine are you trying to find the vehicle equivilant for?

I have an older Mercruiser 5.7L Comp Ski engine. 250hp. It comes in a Ski Ray ski boat.

Would I have to check the engine out for details that would give away whether it is a ford or GM or just assume a GM?

Chevy has two exhaust ports real close together in the middle should be a dead give away. 5.7L is generally assoc. with the Chevy also Ford would be a 5.8L.

Mercruiser 5.7 is a GM 350. But be careful when trying to use "automotive" parts. While some are equivelant, many are marine specific and are not interchangeable; spark plugs for example, and other electrical components.
Why take the chance to save a few bucks when you could really screw up your engine?

chris: what would the difference be for a marine grade spark plug for that engine?

chris: what would the difference be for a marine grade spark plug for that engine?


about $4.50...........

They don't rust into place. Believe me, I've seen it, boats I've worked on.

ok, I was just curiosu because our current Yamaha outboard just uses a certain model of NGK spark plug you can pick up at Canadain Tire (non marine grade) and we havn't ever had any issues.

Yeah, our Yamaha jet ski uses regular NGK plugs, I can't explain that one , it is a two stroke though...

My brother used to have a late 80s MC Prostar 190 with the 351 Ford. Besides the obvious marine equipment bolted to it, starter, alternator, distributor, etc., the engine actually spun the opposite direction of the car version.

In the PCM manual for the 351, there are directions to make it spin in either direction. I assume an automotive engine can do the same.

It's pretty dangerous to assume you can use the automotive counterpart. On a part-by-part basis though, there's quite a bit of crossover. An automotive carb is probably the most dangerous auto-specific item to put in your boat. The freeze plugs in the marine block are brass and therefore won't rust. The oil filter from an auto engine will screw on, but depending on the filter it might not allow enough flow to do anything. Marine filters usually filter less but flow more. Some automotive oil filters will run on bypass almost the entire time if you use them. Don't know about spark plugs. I use Champion marine spark plugs. They cost about the same as the regular Champions.

If you have a Mercruiser inboard, NAPA can do a parts lookup based on your engine serial number and even do a crossover search for equivalent automotive components. Not sure if they can do that for other brands of inboard.

The difference is 1 if you are caught by the coast guard using automotive parts like distributor, carbs, or alternetors or starters off a car, its a huge fine per item!

car or truck chevrolet engines have different cam profiles and compression ratios, most marine motors have stainless valves, forged steel cranks and forged pistons as opposed to cast pistons.

much longer lasting. also brass freeze plugs in block, different headgastket material. etc.

also automotive engine oil is different then marine. Marine oil doesnt break down in the enviroment its in where is automotive oil is much more sensative to breaking down. as long as you change your oil offten you are ok usually. marine oil and fuel filters are different. marine ones usually allow for water seperation in higher volume.

all nautiques prior to i think 2003? are reverse rotation meaning nothing changes over.

Great mis-information

thats alot of mis information. for one nautique stopped using reverse rotation motors in 1988 not 2003

My 2000 has reverse rotation.

sorry you didnt know.reverse rotation is thru the tranny not a reverse rotation motor since 89

G i wonder why i had to use this for troubleshooting wireing issues in both my 91 nautique and my 93?

I MUST HAVE SOME od ball nautique?

o wait, I must have had an odball 91 nautique, and my 93, and my gfs 98 must also be an odball as well?

so what other misinformation did I post? just want to be corrected. I mean the 4 years I spent wrenching on boats im sure my eyes could have played tricks on me?



(Message edited by sanddragon2004 on October 12, 2007)

I really would like to know what are the advantages or of a reverse rotation boat.

just the way they drive, turns easier to the opposite direction. Personally i hate it and like the standard rotation better.

but also, if you are the builder of said engine and you are the only one who makes rr parts then.......


(Message edited by sanddragon2004 on October 12, 2007)

hey matt some times the marine spark plugs are different heat ranges then their automotive counterpart.

Most GM 350s have 210deg theromstats and are designed to operate at a different heat range, while most marine engines have thermostates that operate at about 160-170deg. u are running constant supply of cold water through the motor so it is not going to get as hot as a car engine.

dealers rely on the fact that most people dont know this and jack up the price on a set of plugs that you can get at kragens for 1.49 a peice.

same thing with 2strokes, I can go buy a plug at the dealer for my banshee for 5 bucks a pop. or go to kragens get the same ones for 1.49 a peice. Price gouging at its best. (however the marine industry has a season of operation so they have to make there money in that short amount of time)most of us are not buying props, driveshafts, or even wakeboard equipment in the winter.

(Message edited by sanddragon2004 on October 12, 2007)

What would marine engine oil be?

good question T-bagger

Andy,
you're also saying that marine oil filters have some water separation properties. So the reason my oil doesn't appear milky is because the marine oil filter has removed or isolated it?? Marine filters also have some higher volume capacity??

it has different detergents and moisture inhibitors in it, to keep it from breaking down in a marine enviroment.

You get alot more moisture build up inside a boat engine then any car.

NO sorry i meant fuel filters.

I dont know of many cars that have water seperating fuel filters.

other then diesels.

If you dont have one in your boat ur gonna have problems at some point.

(Message edited by sanddragon2004 on October 12, 2007)

`What's the unique problem of the marine engine? Water. Water promotes rust, corrosion and rapid wear. Freshwater-cooled boats operate cool, which promotes in-engine condensation and rust. Closed-system marine engines tend to operate very hot, which promotes the creation of acids - and engine corrosion. The longer the engine works, the more water and acid build, and the acid and water continue to work after engine shutdown.


Pulled this off the amsoil website.

http://www.go-synthetic.com/marine_boat/marine_boat.html

fuel/water separator is completely different.