MerCruiser 4.3lx shortblock compatibility?

Scott06

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Apr 20, 2014
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4bbl carb currently.
That also raised another question I had for the edlebrock 4.3 marine manifold for the 4.3, It's not clear if I can use the same carb, or if I need to buy theirs?

I also located a "Core" 4.3 out of a 97 S10 for $30.
If I get lucky, I might have a donor for the vortec heads, and if I get really lucky the block is rebuildable.
You can re jet your weber carb for the vortec heads. The weber carb is essentially the same as the edlebrock 1409. There are a few threads here where guys lay out the jetting needed to work on a vortec 4.3

If there is nothing wrong with your current short block take the donors heads to a shop and have them rebuilt. Get marine head and intake gaskets, and intake and you are good to go.
 

Lou C

Supreme Mariner
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Nov 10, 2002
Messages
12,189
That would be a great outcome, just make sure to prep the block by cleaning the sealing surfaces & also all the cyl head bolt holes in the block with a thread chaser. You want to make sure that all the head bolts thread in easily so you get proper torque when installing the cyl heads….
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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If there is nothing wrong with your current short block take the donors heads to a shop and have them rebuilt. Get marine head and intake gaskets, and intake and you are good to go.

The PO states in post #1, his block is toast.
Well I recently bought a new to me boat, and I got one with a crack in the block!
 

Gibbles

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Nov 14, 2009
Messages
2,017
I wish my block was good, the engine runs great and the one time I took it out after purchasing I got to a nice 38/39mph via GPS.

I bet it would go over 40 if I dumped the high five prop and had it trimmed right.
Probably over 50mph if I went V8?

Only real change I want to make is to add some trim tabs to help the butt of the boat get out of the water a little quicker.

I'm almost half tempted to not even bother upgrading to the vortec heads and intake since it runs so well as is.

Option 1: Pull engine, slap marine stuff onto a new/rebuilt shortblock, and send it.

Pros: Cheapest and easiest option, less likely to have things go wrong.
Cons: While I'm in there stuff skipped making me regret my decisions?

Option 2: same as above but with vortec heads and the Edelbrock manifold.

Pros: a little more power
Cons: more cost since I would need to replace the intake + heads, and I would need to mess around with the carb.
Not scared of the carb, but it's just one more thing.

Option 3: upgrade to a 5.7/350

Pros: more power and torque!
Cons: maybe engine mounts?
I also don't know if any of these islanders were ever sold/shipped with a v8.
Also, possible gearing issues, I might need to regear the outdrive?
Having to buy new props either way most likely.


I'm teetering between option 1 and two at this point.
 

Gibbles

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Nov 14, 2009
Messages
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Also I'm curious about camshaft recommendations if I stay with the 4.3.
I saw Melling makes a camshaft that calls out "Marine" for the 4.3 with roller lifters.

I believe this is it: https://www.summitracing.com/parts/mel-22119/make/chevrolet

Looking at the specs, I thought the marine cam had something like .500 lift?

Does this look right?
Other reccomendations?

Camshaft Use:
Marine
Basic Operating RPM Range:
Stock
Intake Duration at 050 inch Lift:
202
Exhaust Duration at 050 inch Lift:
213
Duration at 050 inch Lift:
202 int./213 exh.
Advertised Intake Duration:
271
Advertised Exhaust Duration:
284
Advertised Duration:
271 int./284 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:
0.403 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:
0.409 in.
Valve Lift with Factory Rocker Arm Ratio:
0.403 int./0.409 exh.
Lobe Separation (degrees):
112
Camshaft Gear Attachment:
3-bolt
 

Gibbles

Commander
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Nov 14, 2009
Messages
2,017
I guess another pro for the v8 swap would be a wider selection of camshafts.
 

Gibbles

Commander
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Nov 14, 2009
Messages
2,017
Oh, and since we all like pictures.
here is the external crack I found that resulted in some money back from the seller.

The Main issue is the water I found in the oil. :confused:
if it was just on the side of the block, I would probably just run it as is.
1698358857755.png

Poor guy thought he had rivet leaks, so much Guvit in the bilge... 🧐

When the engine is out, I plan on doing some cleanup, I think in some places it's about 1/4in thick! 😝


One good looking boat IMO!
1698359178905.png

The wake board tower thingy is probably coming off eventually.
Probably when I finally go to repaint the thing, I can have the holes tig welded up before I prime and paint.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Messages
48,178
You can use your current marine cam, which is remarkably similar to the truck cam.

If it was me. 1996 or later 5.7 liter V8 from a truck, new exhaust manifolds, weekend to change it over ....... Then go boating
 

Scott06

Vice Admiral
Joined
Apr 20, 2014
Messages
5,986
Also I'm curious about camshaft recommendations if I stay with the 4.3.
I saw Melling makes a camshaft that calls out "Marine" for the 4.3 with roller lifters.

I believe this is it: https://www.summitracing.com/parts/mel-22119/make/chevrolet

Looking at the specs, I thought the marine cam had something like .500 lift?

Does this look right?
Other reccomendations?

Camshaft Use:
Marine
Basic Operating RPM Range:
Stock
Intake Duration at 050 inch Lift:
202
Exhaust Duration at 050 inch Lift:
213
Duration at 050 inch Lift:
202 int./213 exh.
Advertised Intake Duration:
271
Advertised Exhaust Duration:
284
Advertised Duration:
271 int./284 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:
0.403 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:
0.409 in.
Valve Lift with Factory Rocker Arm Ratio:
0.403 int./0.409 exh.
Lobe Separation (degrees):
112
Camshaft Gear Attachment:
3-bolt
I dont think the heads in as left GM condition can take anywhere close to .500” lift i think vortec may be limited to .430” with machine work
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
48,178
correct, to go over .43", the valve seals need to change and the valve stem guides need to be skimmed.
 

Gibbles

Commander
Joined
Nov 14, 2009
Messages
2,017
Thanks!
The assumption is I'll need to do some replacing of parts due to water intrusion into the oil.
I don't have a picture of it on my PC, but it looked more like Cream vs motor oil.

The PO was also running 5w30... :rolleyes:

I'm half expecting to find stuff rusted, and I'm probably going to want to replace the lifters and camshaft as a set.

however, if the camshaft looks good, I might at least disassemble the lifters to see if any internal damage or rusting happened.
 
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