4.3L Vortec mercruiser cracked block - swap with automotive engine block?

[mmanning63]

Hello,
I've been reading through many many threads, and it seems like I do have hope, afterall...
I have(had) a mercruiser 4.3L Vortec engine on my boat, and it was not winterized properly and received a cracked block in return. some said, "get a new 4.3L Vortec engine out of an old blazer or s-10, throw the old marine parts on the new engine and change out the freeze plugs to brass". Then I got the, "You can't marinize an auto engine, it just doesn't work that way". So, My question is, since I have a non-working marine engine sitting right next to me and now I have a chance to pick up a working 4.3L Vortec engine out of a 96 blazer, can't I just mix-and-match? what else do i need to change out to make this a working marine engine?
Thanks for any help!
-sorry, should have made a better title for this, it is not about a cracked block, but about marinizing an engine..

[Jango]

Shouldn't be a problem changing the Truck Engine to marine. Safety is the primary concern: You NEED TO USE THE MARINE:
1. Carburator or injection system
2. Starter
3. Alternator
4. Distributor
Anything that exposes gas fumes or Electrical spark
If the Truck is a standard shift, the Flywheel should be OK, otherwise change to the marine

[CDK]

Since you have the defect engine with all peripherals, swapping the engine blocks doesn't present any special problems as long as no bolts are too rusty to remove them without damage. Use new gaskets for the exhaust manifold, fuel pump and thermostat housing and put the Mercruiser water pump on because it has a different impeller.

[KnottyBuoyz]

You might want to check with a Mercury marine parts dealer the cam shaft might have a different profile.

[CDK]

The Merc dealer probably is inclined to say the cams are different because that has been suggested lots of times.
A fact is that there are "performance cams" offered by 3rd parties, but I doubt Mercruiser installed these in a standard engine.

mmanning63 has both the marine and automotive engine: I hope he lifts the camshaft covers from both, looks at the shafts and posts here whether or not they are different.

I am waiting with bated breath!

[Jango]

It will be difficult to see a difference between the Truck and Marine cams. I was told, in most instances, they are the same cams. Unless performance is noticeably different, I would " Leave well enough alone " It's a mistake to install a " High Performance" Auto Cam. Boats need alot of torque, like a truck, especially at lower RPM's.

[broke_not]

"You can't marinize an auto engine, it just doesn't work that way".

Often said by, (but never really explained by), "boat" mechanics.

Oh, they'll say that the marine *version* of an engine has "special" this or that, but try to nail 'em down on what exactly "special" means.

Then ask 'em why the "special" bits can't be unbolted and swapped between the engines you're talking about.

There's nothing magical and mysterious about any of it. They do want you to think there is though.....



I guess for extra giggles, you could ask them how the "marinize" term came about in the first place. It seems as though at some point someone took an engine originally designed and built for something else.....and then "marinized" it.

[L67Supercharged]

Originally Posted by broke_not

Often said by, (but never really explained by), "boat" mechanics.

Oh, they'll say that the marine *version* of an engine has "special" this or that, but try to nail 'em down on what exactly "special" means.

Then ask 'em why the "special" bits can't be unbolted and swapped between the engines you're talking about.

There's nothing magical and mysterious about any of it. They do want you to think there is though.....



I guess for extra giggles, you could ask them how the "marinize" term came about in the first place. It seems as though at some point someone took an engine originally designed and built for something else.....and then "marinized" it.

To expand on this, I often wonder if there's a real difference between parts, or if it actually matters. I'm a 22 year old college student and I work at AutoZone part time until I graduate, and the store I work at is located right next to a bay and a marina. People come in all the time to buy parts such as alternators, starters, distributors, etc. They'll come in and say "I need a starter for a 302 engine" and when I ask what year vehicle I get "Oh it's for a boat" and so I have people putting auto parts on their marine engines all the time, but yet I don't see boats blowing up in the bay. So I'm not entirely convinced.

[KnottyBuoyz]

Originally Posted by L67Supercharged

To expand on this, I often wonder if there's a real difference between parts, or if it actually matters. I'm a 22 year old college student and I work at AutoZone part time until I graduate, and the store I work at is located right next to a bay and a marina. People come in all the time to buy parts such as alternators, starters, distributors, etc. They'll come in and say "I need a starter for a 302 engine" and when I ask what year vehicle I get "Oh it's for a boat" and so I have people putting auto parts on their marine engines all the time, but yet I don't see boats blowing up in the bay. So I'm not entirely convinced.

The alternator is a no no in a gas engine boat for sure. Marine alternators have screens (spark arrestors) preventing sparks from igniting any fuel vapours in the engine compartment. Yes they do blow up without them. I've seen couple of boat fires caused by this in my 30 yrs in the Coast Guard. The starters are the same. Don't know about distributors but I doubt there's much difference.

[broke_not]

To expand on this, I often wonder if there's a real difference between parts, or if it actually matters....

Yes, there are differences in some of the parts. My intention was to point out that somewhere along the line an engine was "marinized", (What?? How could that have happened?? Marine engines are by their very nature special!!), and that's why the term "marinized" exists. If the "marine" engines we're talking about here existed in the *complete and separate breed* fashion some would like you to believe, that would change the game significantly for the DIY-er.

All too often, marinizing is treated as if it's mysterious....and it's really unnecessary and bordering on the ridiculous. You take an engine and bolt on the required bits needed to make it suitable for the application. If you had an engine in your boat that wasn't winterized and cracked or something similar, you obtain a replacement.....and transfer some parts.

Unbolt/bolt. Repeat as necessary.

Rocket science it ain't.

[Frosty]

He already has the alternator, starter, carburettor and camshaft but I would not change the cam as it is already in a truck type application needing torque.

Just swop it all over, you do not need stainless head gaskets and stainless water pumps (if it is stainless) because you are a fresh water cooling, but if you got the pump then you could swop.

A good days work, nice simple job.

In Uk in the 60's there was no such thing as a marine engine for sports boats, ALL boats had car engines in them. Car carbs, alternator (or dynamo) and I never ever saw one on fire ---ever.

[Lt. Kludge]

Originally Posted by KnottyBuoyz

Don't know about distributors but I doubt there's much difference.

A UL Listed Marine Distributor must pass an explosion containment test. An explosive mix of propane is put inside the distributor with a remote detonator, while the whole distributor is placed in a chamber also containing an explosive mix of propane. Inside charge is detonated and if the outside charge ignites the test fails.

You may get away without using the "Marine" components. But that is because the system is intended to be safe in the event of a single point of failure. And 99% of the time there won't be any failure. Like a fuse in ones home. 99.9% of the time a copper penny would work even better.

[powerabout]

Dont forget GM also sell the marine version of that engine so any GM dealer can tell you if the cam is the same in the marine engine versus any other spec engine.
Merc only change cams in the performance engines, stock engines come with GM's marine cams
http://www.gm.com/vehicles/innovatio...ne_engines.jsp

[gonzo]

Distributors on boats have a spark arrestor too. It is only a pipe with an elbow. The fuel pump is different too. The camshaft will have a different profile but fits the other block. The exhaust valves are Stainless in a marine engine, I don't know what a Blazer has. The oil pump is a low pressure high volume. It is about twice the height, but the pressure spring is weaker. The harmonic balancer is a bit different too, but it will fit the other engine. The head and intake manifold doesn't have EGR or vacuum pickup.
L67Supercharged: if you are selling automotive electrical items for boats, it is illegal and dangerous.
There are some snide and slanderous remarks about marine mechanics in this thread. I am one and can tell you exactly what the difference is between the engines.

[lilrobobx]

Not sure if this thread is still being followed, but i am going to post info some info about differences in a 1998 Vortec marine engine versus a 2006 Vortec automotive engine for all those wondering, because it is my understanding that actual bearing clearances are also TIGHTER on the automotive engine and this would make sense to me as the engine requires 5w20 oil(very thin) and the marine version requires 20W40(pretty thick) and if you use the thicker oil in the auto engine, i would imagine it to be similar to an oil starvation of the bearings and probably cause some excessive wear...not quite sure yet but i will be taking measurements and recording part number differences on everything...both are in very good condition, any thoughts or questions, suggestions...shoot me a line!
Rob