Mercruiser 4.3L question

Can any ony tell me what the differance is between the differant generations of the Mercruiser 4.3L. I am doing reserch on the engine and see it is split into several groups by year. I am most intrested in the differances between 1980-1989, 1990-1995 and 1996-1999.

Now the reason, my brother is considering getting a running fully dressed mercruiser 4.3L that was rebuilt last year with a truck block for a really great price. We would like to re-build the engine useing a proper remanufactured marine block from usengines.com but the seller dosnt know the origional manufacturing year of the engine. So we are trying to figure it out via the rest of the engine.

It has the plastic cover on the flame arestor and reads 4.3 liter in large letters and underneath says thunderbolt ignition/power steering. But dont want to put my trust in a cover that can be added or removed willy nilly.

I just dont want to get in a spot were we have the motor and when we order the new long block things dont bolt on as they should.

Thanks

Re: Mercruiser 4.3L question

I'm assuming the mercruiser serial number plate that is supposed to be stamped to the side of the engine is missing?

Re: Mercruiser 4.3L question

Can any ony tell me what the differance is between the differant generations of the Mercruiser 4.3L.

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Ayuh,... I don't write Novels, 'n that's about the size of the 4.3l Chevy history...
The Big changes are 89 when the balance shaft showed up, 'n 96 when Vortec heads were Intro'ed...

How about you tell Us what you've got....
Pictures work nicely for such things,...
Any Numbers found on it as well...

Why do ya wanta replace a motor rebuilt Last year,..??

Re: Mercruiser 4.3L question

....Yes the Serial number plate is not there

The reason we are looking to rebuild is because the seller says it was rebuilt using a truck block, I am reading between the lines and considering the cost of the engine thinking it was not a new truck block prob something out of a scrap yard since you can pick one up for just a few hundred bucks, so we are looking at it from the aspect that it is already well used and we dont want it crapping out on us once in the boat. So by getting the engine breaking it down, picking up a brand new long block with a full 7yr warrenty, all new gaskets, cleaning manifolds and such and making any needed upgrades we come out the other side with an engine that has all its vitales covered under warrenty, is reliable, has no hidden issues and give us peice of mind. We will basicly walk away with the next best thing to brand new but at half the cost staying in a $3500 budget.

So my issue is, I need to be able to find out the proper year group this engine belongs to so i get the proper long block to rebuild it with.

Hear are the pics the seller has up,

Re: Mercruiser 4.3L question

Are ya going to replace that 3.7 with the 4.3?

Re: Mercruiser 4.3L question

Lets break this down into some meaningful chunks.
1) In your first post you said the first engine was rebuilt a year ago using a truck block. Rebuilt how and by whom? It doesn't matter if the block came from a truck since that would be the same block that would have been used in the boat and the camshaft (if from the truck) is close enough to a marine grind you wouldn't notice the difference.

2) So you go on to say you want to rebuild using the proper engine from US Marine Engines. What makes you think THAT block would not have seen a prior life in a truck. Actually, once an engine has gone through the gazillion heat/cool cycles they do over 100,000 miles or so they make great race engines because the castings have stabilized as much as they are going to and if rebuilt properly will run as long as a brand new engine fresh from GM.

3) You seem to imply that you are buying both engines (the one from US Engines would be a long block) and then you add the stuff from the original (what you called the truck engine). If that's the case you are spending way more money than you need to. If you don't know who did the work or how extensively the first motor was rebuilt, why buy a second one. Have the first one professionally rebuilt and be done with it. Have the rebuilder add a marine cam and you will end up with the same thing you get from US Engines.
'
4) If the engine came from a truck you can look at the pad on which the engine code is stamped. From that any GM dealer can ID the engine (or you can google GM Engine Code ID). If it's a marine engine you should find an engine tag. If you stay with the rebuilt truck engine you don't have to worry about the interchange stuff -- it's already done for you and you spent a lot less money.

Re: Mercruiser 4.3L question

Joshua Nichols said:

Are ya going to replace that 3.7 with the 4.3?

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Yes i am and already have the engine to do so, but this pertains to my brother project. i am helping him in my spare time. I had a really nice 4.3 fall in my lap so to speak that going in my boat come spring.

Re: Mercruiser 4.3L question

Silvertip said:

Lets break this down into some meaningful chunks.
1) In your first post you said the first engine was rebuilt a year ago using a truck block. Rebuilt how and by whom? It doesn't matter if the block came from a truck since that would be the same block that would have been used in the boat and the camshaft (if from the truck) is close enough to a marine grind you wouldn't notice the difference.

2) So you go on to say you want to rebuild using the proper engine from US Marine Engines. What makes you think THAT block would not have seen a prior life in a truck. Actually, once an engine has gone through the gazillion heat/cool cycles they do over 100,000 miles or so they make great race engines because the castings have stabilized as much as they are going to and if rebuilt properly will run as long as a brand new engine fresh from GM.

3) You seem to imply that you are buying both engines (the one from US Engines would be a long block) and then you add the stuff from the original (what you called the truck engine). If that's the case you are spending way more money than you need to. If you don't know who did the work or how extensively the first motor was rebuilt, why buy a second one. Have the first one professionally rebuilt and be done with it. Have the rebuilder add a marine cam and you will end up with the same thing you get from US Engines.
'
4) If the engine came from a truck you can look at the pad on which the engine code is stamped. From that any GM dealer can ID the engine (or you can google GM Engine Code ID). If it's a marine engine you should find an engine tag. If you stay with the rebuilt truck engine you don't have to worry about the interchange stuff -- it's already done for you and you spent a lot less money.

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I am simply looking for some insight in properly dating the engine. No matter what engine we end up with it will be rebuilt with a profesionaly remaned or new long block with warrenty and all new insides. What ever engine we do end up with is just for the peripherals, thats it.

regardless if i buy a long block or send the one from the engine it self to a shop it will cost the same amount, just my way is faster cause i dont have to wait for a turn around.

I am not going to trust that the block it has now as being the right year.

Re: Mercruiser 4.3L question

regardless if i buy a long block or send the one from the engine it self to a shop it will cost the same amount, just my way is faster cause i dont have to wait for a turn around.

I am not going to trust that the block it has now as being the right year.

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Ayuh,... That's just Insane rebuilding a rebuilt motor,...
Especially before even runnin' any diagnostics on it...

It must be nice having more Money than sense...
Well,.... Maybe not...

As far as trusting whether the block being the right vintage,...
It is, what it IS...

Is there a mechanical fuelpump on it,..??
Can't see the top of the timing cover,... That's another clue...
The casting # is on the aft flange, behind the portside head...

Re: Mercruiser 4.3L question

I can tell you that the Mercruiser setup is from the 88 to 92 time frame. I can just barely see the mechanical fuel pump on the engine and the clear (yellow) hose that goes from the fuel pump to the carb. Starting in 93, the electric fuel pump was used, and the mechanical fuel pump boss on the block was not usable.
It does have the Thunderbolt IV ignition.
Here is a link to the OEM service manual that covers that engine. http://www.4shared.com/document/1FdjddET/Service_Manual_07.html

I would also start the engine on the ground, run it and make sure it runs, then do a compression test on it before just replacing the longblock for no reason. It may be in great shape, only way to find out is buy testing.
If the compression test is ok, and you are curious, you could always pull the oil pan and look at the rod and main bearings. If you have good compression, and good bearings you will be wasting your time and money replacing it.

Re: Mercruiser 4.3L question

solar7647 said:

Yes i am and already have the engine to do so, but this pertains to my brother project. i am helping him in my spare time. I had a really nice 4.3 fall in my lap so to speak that going in my boat come spring.

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awesome... bet it feels under powered with the 3.7... should be able to really tell a difference

Re: Mercruiser 4.3L question

Joshua Nichols said:

awesome... bet it feels under powered with the 3.7... should be able to really tell a difference

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It really dosnt feel under powered with the 3.7l. It has no problem with any of the task that I use the boat for. I decided to switch because I got the 4.3 for free and its just better on maint cost. plus if the need for a sale ever comes about it will be easyer to sell. I figure I will be able to regain the money I put into the 3.7 last year in just selling the periphrials on ebay, probly regain 85% of my money in just the head, intake, exhast and heat exchanger.

Re: Mercruiser 4.3L question

Don S said:

I can tell you that the Mercruiser setup is from the 88 to 92 time frame. I can just barely see the mechanical fuel pump on the engine and the clear (yellow) hose that goes from the fuel pump to the carb. Starting in 93, the electric fuel pump was used, and the mechanical fuel pump boss on the block was not usable.
It does have the Thunderbolt IV ignition.
Here is a link to the OEM service manual that covers that engine. http://www.4shared.com/document/1FdjddET/Service_Manual_07.html

I would also start the engine on the ground, run it and make sure it runs, then do a compression test on it before just replacing the longblock for no reason. It may be in great shape, only way to find out is buy testing.
If the compression test is ok, and you are curious, you could always pull the oil pan and look at the rod and main bearings. If you have good compression, and good bearings you will be wasting your time and money replacing it.

Click to expand...

Thanks you very much Don that is what I need to know. We fully plan on testing the engine once baught, but my brother has his mind set on the new long block and its his money.