It killed the cat, so why not

[brhodes]

My curiosity is getting the better of me. I am taking a USCG Boating Skills and Seamanship 13 week course. We are in week 2, and in a Chapter titled "which boat is for you". Our instructor has some years behind him, served in the Navy, used to sell boats at a dealer, you get the picture. He was discussing the differences between a I/O marine engine and a regular truck/car motor, citing explosion proof etc, all the stuff that comes up on this board often. He then made a statement that the metals used in a regular automotive/truck engine are differrent than those used in marine engines for corrosion resistance. This threw me, as I've often read at least the blocks are the same. Has anyone ever heard of this?

 

[ziggy]

Re: It killed the cat, so why not

sure, at the very least, core plugs, head gaskets, and spark plugs use different metals than autos. all for corrosion resistance. the blocks are the same as autos though. it's generally the peripherals that are marine duty.

makes sense imho, water promotes corrosion. especially for dissimilar metals. think about all the fasteners on a boat too. on my boat, many are stainless steel. like upholstery staples, screws that hold the cap to the boat hull, anything else that's screwed to the boat too.

 

[brhodes]

Re: It killed the cat, so why not

Ziggy, this is what i've heard all along, but he was implying the blocks used different metals. I didn't want to turn it into a motor discussion as that was not the point, and my knowledge of motors is slightly above none. I hope I never have to really know if they are the same cause you know what that would mean, but.......

Thanks for the input.

 

[Don S]

Re: It killed the cat, so why not

He then made a statement that the metals used in a regular automotive/truck engine are differrent than those used in marine engines for corrosion resistance.

I have heard that many times, also by those that assume things, like your instructor.
The cast iron used in the engine block and heads is the same as any automotive engine.
General Motors, as an example, uses their regular cast iron engine castings in the assembly, there are special ground cam shafts, and brass core plugs and either composite or SS ringed head gaskests where they contact cooling water, but that is it.
That information comes from both Volvo and Mercruiser tech schools that I have attended.
I even have it in one of the training manuals, if I find it, I will post it.

 

[HT32BSX115]

Re: It killed the cat, so why not

served in the Navy, used to sell boats at a dealer, you get the picture.

Yeah, I have met people like that. It's sort of like a truck driver or truck salesman thinking he knows everything about diesels when neither know anything about anything but profess too!!.... a few simple questions always reveals the blowhards.

Just being the Navy doesn't make you more knowledgeable about pleasure boat engines/drives any more than being a USAF or airline pilot makes you knowledgeable about small airplanes and engines!!



regards,


Rick

 

[StevNimrod]

Re: It killed the cat, so why not

+1 to what Don said.

A person can have respectable credentials + still get it wrong sometimes, or have no credentials and get it right.

There are a lot of popular beliefs about boat engines - all have four bolt mains, forged internals, beefier blocks, and a host of other things that are different from automotive applications.

For the accessories, yes; there are concerns with spark/flame suppression. But when I took my 94 Merc 350 apart the block was not "special" (by casting number, '638), had two bolt mains (like it says in the Merc service manual for that model), and a cast crank (by casting number) and pistons.

When I put the replacement together (96+ vintage) I found that the Merc head gasket was actually a GM part number (that was a stainless core, but still a factory GM part) and the intake manifold gasket was a GM part.

Several years ago a popular auto magazine published an article about GM's Vortec 350 heads and said one casting number was superior than the other. A short time later they published a retraction, but to this day guys will ask for one casting number ('062) rather than the other ('906), because "all '906s have the 'flow killing' hardened exhaust seat inserts". Funny part is, not even all '906 castings have the hardened seat inserts. I've got two sets in the basement; one set with inserts, one set without. For marine applications a lot of guys are after '906s because of the hardened inserts but fail to realize that not all '906s have 'em.

 

[proshadetree]

Re: It killed the cat, so why not

You just gota love those specialized experts. Didnt you know there is a special cast iron used for boat motors? And special aluminum for the pistons? They are assembled on a special line in a special place. Very hush hush Shhhh! Dont tell nobody