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Engine block differences

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mike.l

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Hi I have a marine 4.3 block from 1990 block casting number is #10105867 which is cracked i found a chevy truck 1990 s 10 the block number in that is not the same (Chevy did a lot of tinkering with the 4.3 around that time) its #is 1017 2756. Do we have a guru on the forum that could unravel the mystery on these blocks as i would like to buy the Chevy engine and rebuild it through the winter time using all marine parts from cracked block and present it as a drop in next spring - summer thanks Mike
 
Looks like the balance shaft engines came out after 1991.
Are both of these non-balance shaft engines?


[FONT=&quot]1987-1994 without balance shaft - metal timing cover[/FONT]
[FONT=&quot]1992-2004 with balance shaft only - composite timing cover
[/FONT]
Apparently the camshaft from a balance-shaft cylinder block will not work in a non-balance-shaft cylinder block due to different length camshafts.


[FONT=&quot]Although this pertains to trucks, you can read more info here.

[/FONT]https://www.s10forum.com/threads/balance-shaft-cam-vs-non-balance-shaft-cam.529890/[FONT=&quot]

[/FONT]
 
RicardoMarine said:
Looks like the balance shaft engines came out after 1991.
Are both of these non-balance shaft engines?


1987-1994 without balance shaft - metal timing cover
1992-2004 with balance shaft only - composite timing cover

Apparently the camshaft from a balance-shaft cylinder block will not work in a non-balance-shaft cylinder block due to different length camshafts.


Although this pertains to trucks, you can read more info here.

https://www.s10forum.com/threads/balance-shaft-cam-vs-non-balance-shaft-cam.529890/
Click to expand...
Both these engines are pre balanced shaft only difference i can find any info on is they could be 2 bolt or 4 bolt on the lifter retainers and the block #10172756 was built either way thanks for the link i will read and digest mike
 
The short answer is that truck engines are different enough from marine that you really should go with marine if possible.
I'll add that the amount of time and effort to rebuild including parts and machine work is often 20-50 percent more than the cost of a reconditioned engine that's ready to install. If you can find a good running take-out that's complete, then that should be option A as it'll be the cheapest and least painful. In this area ( Mid Atlantic ) these come up on craigslist very often.

https://baltimore.craigslist.org/bpo/d/westminster-volvo-penta-43l-v6-motor/7149723099.html
 
Last edited:
mike.l said:
Hi I have a marine 4.3 block from 1990 block casting number is #10105867 which is cracked i found a chevy truck 1990 s 10 the block number in that is not the same (Chevy did a lot of tinkering with the 4.3 around that time) its #is 1017 2756. Do we have a guru on the forum that could unravel the mystery on these blocks as i would like to buy the Chevy engine and rebuild it through the winter time using all marine parts from cracked block and present it as a drop in next spring - summer thanks Mike
Click to expand...

Ayuh,..... Is the hull worth the investment of the time, 'n money,.....

If yer in love with the hull, Up-date yer motor to a recent production 4.3l Vortec,......

You can pick up a pile of horsepower, 'bout 225 hp, with vortec heads, 'n a 4bbl. carb,.....
 
Ditto what Bill wrote. And you can find a LOT of boats with plenty of life left in them for what you are gonna spend on rebuilding an old 4.3. Maybe switch to a boat that has outboard power. Much easier all around.
 
Hi!
This is Elliott,
I do have a complete 4.3 from Chevy S10, and my Maxum 1800 with a cracked block 4.3, ( Mercruiser )
So can I swap the whole motor ( long block ) to my Maxum? Original exhaust from Mercruiser, fit right to the S10 motor,
Please advise if it works or not.

Thank you
 
Where do you find the engine block casting number? Id really like to find out exactly what 4.3 motor was put into mine. I was told it was a 1990 truck motor, and that's it.... Thanks Kirk
 
I think this thread on the iboat forum has the generation differences and casting info https://forums.iboats.com/threads/complete-history-of-the-4-3-liter-with-casting-numbers.693935/

about the swap yes the complete long block from a truck will fit. Yiu need to replace the head gaskets with marine head gaskets and put brass freeze plugs in, and use a marine water pump.
depending on year of boat 4.3 and donor 4.3 there could be some generational differences that could affect accessory mounting intake bolt pattern

if you are going to do get a 96 and up vortec head engine withe the 8 bolt intake these will be a upgrade in power vs an earlier 12 bolt intake engine
 
If you don’t mind me asking…..What is the significance in swapping the head gaskets to marine head gaskets? I understand the reason for brass freeze plug, but what is the difference between a marine water pump vs marine?

I went through that whole thread on the 4.3 you provided, but still couldn’t find “Where” those block numbers are stamped. Can these be seen with the engine installed? Thanks, Kirk
 
on the head gaskets, the marine versions are very corrosion resistant...biggest impacts are when raw water cooling is used....

The marine water pumps (as in circulating pumps on the engine blocks) typically have a bi-directional impeller on them and the better ones have the upgraded bearings and seals though not everybody makes those changes...
 
Thanks for your reply. The engine was replaced on mine right before I purchased it with a truck motor. And the previous owner didn’t have much info on it. I had the starter, fuel pump, and brass freeze plugs changed out to marine standards by a shop, along with a water fuel separator installed. But nothing else. I was just curious…. Kirk
 
When I worked in the shop and did those kid of swaps, we changed the fuel pump, starter, freeze plugs, head gasket(s), and distributors. On the few reverse rotations we did, they typically received new marine grade circulating pumps as they were all complete rebuilds (vs swap-ins)...

If you have raw water cooling, I'd suggest adjusting the budget for the head gaskets as its much less hassle to eliminate the issue before it occurs...
 
Mako has you steered straight on the head gaskets and circ pump. Over time in raw water they will degrade. The circ pump also may not turn the same direction … so marine is bi directional and has cast impeller vs stamped

In the end there are fewer differences between truck and marine engines but certainly some needed mods for longevity
 
That’s a bit confusing about the circulation pump turning the same direction. I mean I always assumed that engine rotation and fan belts all traveled in the same direction. But I never honestly gave it any thought.

I can see where salt water can be more corrosive than a closed system running antifreeze. But I run ours mostly in fresh water, and when we fish the bays I always flush it with salt away and fresh water within a few days of returning. I did have the soft plugs changed out to brass already by a shop, but I’m not sure about the distributor. What’s the difference between the marine distributor and a truck?

Replacing head gaskets is something I would have to take into a shop to do, and would most likely be pretty expensive. I’m not a mechanic per say, but do a lot of my own repairs and all the maintenance. If I can avoid having these upgrades done though keeping it flushed properly and good maintenance. I’d prefer not to do the heads. Changing a water circulation pump wouldn’t be a big deal if she ceased up on me. I’d probably tackle that myself. Thanks for the replies gentlemen. I appreciate it. Kirk
 
Its not as you describe.

Stamped steel automotive head gaskets will rust away in fresh water as in salt water it just takes a bit longer.
Marine head gaskets are stainless steel typically.

This big difference in engine water pumps is, Marine uses a bronze impeller vs Auto which uses a stamped steel. The stamped steel will rust away as described above. The blades/fins are angled for its direction (normal or reverse).

The Bi-directional is for reverse rotation engine use also as many dual engine boats which use one reverse rotation engine.
The blades/fins are straight and will work in either rotation.

The bearings seals are a heavy duty option used on marine.
 
Wow! I didn't know you could run a combustion engine in either direction. But i have seen boats with duel engines and the propeller shafts rotating in opposite directions. I never really thought about it too much. I just figured that was done in the gearing somehow, not the motor.
 
Todays dual I/O's and Outboards use a reverse rotation lower unit so both engines spin the same.

Inboard dual engine boats use/used both standard and reverse rotation. Not sure if they are used much anymore.
 
The marine distributor is ignition protected (screened vent in the base) and the advance curve is set up for marine use. Do not use an automotive distributor in a marine gas inboard, same for alternators, starters and fuel pumps & carburetors.
Definitely swap the head gaskets for marine, they are designed for raw water cooling.
 
Head gasket longevity .... with a
louc said:
The marine distributor is ignition protected (screened vent in the base) and the advance curve is set up for marine use. Do not use an automotive distributor in a marine gas inboard, same for alternators, starters and fuel pumps & carburetors.
Definitely swap the head gaskets for marine, they are designed for raw water cooling.
Click to expand...
With a truck motor and std auto head gaskets, what would be the difference in longevity with a fresh water cooling system? That would be a project i would need to take to a shop, and most likely be expensive. The fuel pump and starter has been changed over, as well as soft plugs in the block. i'm unsure about the alternator or distributor. Kirk
 
most of that would depend upon the content of the water you boat in...pH, dissolved minerals, etc...

a vacuum advance (or a 'window' where it was) is a very good indicator of a non-marine-rated distributor...the alternators are not so easy to spot. a few good pictures would be helpful in spotting a potential problem on either...
 
It’s a damn shame I don’t have access to the guy who actually swapped my motor out before I bought this boat . I have no idea what he swapped out when doing it, and what he didn’t… but I suspect it wasn’t much. it’s quite possible the alternator was used from the stock engine, but I highly doubt the distributor was swapped out. I’ll have to look closer and get a few photos.

Although I’ve never checked the compression on this one, she’s got plenty of power for a little two barrel carb V 6. This 19’ deep V glass hull with the Cuddy cabin is heavy, but with the right screw it performs surprisingly well. Kirk
 
the marine components will say SAEJ1171 on them somewhere.

if the distributor has a vacuum advance can it is not marine as they done use vac advance.
 
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