Settle the debate

[KayKook]

A newbie acquaintance to boating seems to think he is 100% correct about marine engine vs. automotive engines. I think he is missing a few points. Your thoughts ?

Same rules do apply for a boat or car engine. Internally, a 5.0 VP/M or 4.3 uses the identical parts to your buddies old GMC Jimmy or 1985 Camaro ZZ8. There are no such thing as "marine" blocks, heads, pistons, rings, bearings. It may have different accessories installed, but under those special marine carbs and ignition systems... it's no different then what's cruising the streets in 1980.

The only special marine parts that are needed per USCG are distrubtor, alternator, starter, and back fire proof filter on the carb.

The rest are just gimmicks to sell you special "marine" parts. If these no name brand "marine" parts were so great and better then automotive stuff, why are not people using them on their cars??

 

[Ididntdoit]

He's right - but wrong. His explination is oversimplified. For example marine cams are often different to prevent water intrusion (less overlap) Also, many marine engines used to have heavy duty forged internal parts and 4-bolt mains (more like a truck engine). But fundamentally he is correct a 305 or 350 or 454 chevy is just that and differs little from the car version

 

[jitts3]

Brass freeze out plugs is another. Think of it like this too. Your car cruises at 2,000 RPM and that's about it. A boat cruises way higher. The longevity at that RPM is in the cam. But I wouldn't pay marine prices on belts, bearings and so on.

 

[Southpaw II]

Also, Mercruiser gas engines have roller cams and different bearings. Yes, the base block is the same, but even that is modified.

Don

 

[KayKook]

I guess there is not much of a debate then. His over simplified version is essentially correct except for cam, valves, a few bearings and freeze plugs. Thanks guys.

 

[330DA]

Here is a link to Marine Engine Digest about this subject.

http://www.marineenginedigest.com/specialreports/marinevauto.htm

Basically, it confirms what Ididntdoit and others have written, but with a few more differences.

 

[keokie]

Depends on the engine. For example, the old 454 and 502 EFI mags had forged internals (cast for cars) different cams, valve springs, etc.... Not to mention an entirely unique fuel injection system with its own plenum, intake manifold, and ecm program.

Old Merc 470's were an aluminum block cast by Merc with a 460 head with different springs.

 

[KayKook]

What about just the small block V8's ? The 5.0L and 5.7L specifically. I see some had 2 bolt and some had 4 bolt mains, is that correct for marine engines, or only for automotive ?

 

[Gunn]

What about just the small block V8's ? The 5.0L and 5.7L specifically. I see some had 2 bolt and some had 4 bolt mains, is that correct for marine engines, or only for automotive ?

I've had older cars with both 2-bolt and 4-bolt mains. Not sure about marine engines, but I would -assume- that marine engines were 4-bolt mains, due to the higher operating RPMs...

 

[fwebster]

In addition to the above, marine head gaskets are stainless steel, intake manifolds are different, circulating pumps are different, pistons are different, clearances are different............there are so many subtle differences that about all you can say for sure is that the base castings are from the same foundry.