omc 4.3 block question

[boatproblem]

I have a 4.3l not positive of the year, but the boat is a 86. I had the block crack on both sides and found a whole lot of water in the oil. So the block is done for. Now my question is.... when looking for a replacement 4.3 what do I need to do? I have found numerous motors for a couple hundred bucks. are there any differences between the blocks of the omc and the chevy? besides the drain plugs? Are there any block differences that should matter per year? Are the vortec blocks different? I want to reuse my heads and intake manifold and all that stuff if I can cause this motor was super nice. It appeared to be rebuilt not to long ago. I know my way around cars, but this is my first boat. And was not sure if omc made changes to the blocks besides the plugs, or if there was anything I needed to look out for. thanks.

 

[180shabah]

Re: omc 4.3 block question

CORE plugs are different - head gaskets are different - cam is different.

87+ blocks are a 1pc rear seal and will not work with your coupler. 92+ blocks require an electric fuel pump. Vortec heads (on any block) require a different intake manifold.

Have your heads inspected before you decide to reuse them.

 

[boatproblem]

Re: omc 4.3 block question

As the hunt continues I have further quesitons. The 4.3 thats in it, is an 85. Which as I am finding out is going to be a little tougher to get a block than first anticipated. I am going to have the heads checked. I noticed all the gaskets were blue. Are those all marine gaskets? THe head gaskets were metal.

I have a couple of removal questions. I have stripped the motor to just a short block on the boat. Do I have to remove the outdrive to remove the motor? And if I do not have to remove the outdrive, then do I have to remove it to install it? I have read about the alignment that needs to be done, and was wondering if I did not have to remove the outdrive, and the motor bolts to all that stuff like a transmission, would it still be in alignment?

Once I get this motor out, the rest is no problem, I can rebuild this thing in a few hours. Minus machine work. And parts availability. Its just putting it in, and what would be the most time affective. The outdrive and such was serviced last year, and this engine before the cracked block was fully rebuilt a few years ago.

So I guess what I am asking ultimately is there any way I can just slap this thing out and slap a new one in and be fine? I have more than good room for forward movement of the motor. I would say over 12 inches.

 

[cr2k]

Re: omc 4.3 block question

Pull the drive. It makes it so much easier. Yes you will need to remove it anyway to realign the coupler. Make sure you put plenty of spline grease on the drive shaft when you put it back together. Couplers are expensive so take care of yours.

 

[boatproblem]

Re: omc 4.3 block question

oops

 

[boatproblem]

Re: omc 4.3 block question

ok thanks for the advice. I am still hunting for a block and will update after I get the new block built...

 

[chevinrude]

Re: omc 4.3 block question

Would it be possible to use a 4.3 block from a Chevy S-10? I have two S-10's, a late 80's model and an early 90's both with the 4.3...

Just throwing out a suggestion, not even sure if it would work

 

[180shabah]

Re: omc 4.3 block question

While it is possible to use an automotive block, he still has to stay with the same vintage as noted above.

 

[boatproblem]

Re: omc 4.3 block question

If it is a 4.3 pre 87. It would work.

 

[180shabah]

Re: omc 4.3 block question

If it is a 4.3 pre 87. It would work.

Yes.

 

[ElCameeeno]

Re: omc 4.3 block question

I am following this thread as I am in the same boat. Hah! That phrase makes sense now!

I am finding that there are many variations of the 4.3. They were built in two plants and the internals are not even the same between them.

I have located a '98 block that I am going to take the plunge on for my 2000 boat. Gonna cross my fingers.

 

[180shabah]

Re: omc 4.3 block question

Don't mix the internals, you'll be fine.

 

[glasstream86]

Re: omc 4.3 block question

i have the same block and i took the intake manifold off and i found the valley was cracked on both sided inside of getting a new block i got some high heat jb weld and marine putty on
my block was not cracked through to the piston housing
i have ran it a few times no water in the oil anumore so we will see how long it will hold

 

[boatproblem]

Re: omc 4.3 block question

Mine cracked inside, and had water all in the oil.


I do have an important question as far as motor selection. I have been doing extensive research as much as I can find. Now hear is my question. Is the only motor I can use an 85?

I have read all about the two bolt main, and according to what sites I have looked up, in 86 they switched it to a 1 bolt main, and even some 85 model vehicles have the 86 motor in it. So.... as I am hunting I am just unsure whether or not to track down an 86. I have called every local machine shop yesterday and they are trying to find a block with a matching casting number, but if that fails, what other options do I have? If I found a later block, what would I have to change to make it work? Or is my drive completely wrong for any other variation of the block?

 

[boatproblem]

Re: omc 4.3 block question

i have the same block and i took the intake manifold off and i found the valley was cracked on both sided inside of getting a new block i got some high heat jb weld and marine putty on
my block was not cracked through to the piston housing
i have ran it a few times no water in the oil anumore so we will see how long it will hold

After reading this... I thought...... huh... I have not looked at the valley at all, since I decided to strip the motor at night. I looked just a second ago... and wow cracked on both sides. One side is a visible feelable crack about 3 inches long. on the other side, one crack about an inch long you can see but not feel. Also I noticed a few other smaller cracks, because I see the rust line. Now my problem. I already JB welded the outside of the block that was crack under the exhaust manifold. So thats done, but my motor is now a short block in the boat. Do I opt to JB and stick together. Or do I stick with the rediculous hunt of finding a specific block. I purchased the boat for 900 bucks, hoping to have it replaced by another 4.3 for less than 500 bucks. But with the locating of this casting number block is silly. And so I stuck whether to try just jb welding and make it through till I can actually locate a good omc 4.3 block. Or hunt and hunt for a auto block with the same casting numbers, and have it be an automotive block and still be not right. I do not have a whole lot of money, but I do have a whole lot of time. What would you do?

 

[boatproblem]

Re: omc 4.3 block question

Yes.

I have a question about the drive. I have a cobra drive. does that matter to which engine I can use?

 

[glasstream86]

Re: omc 4.3 block question

some ppl say it does matter but i placed a mercruiser v-6 motor on my cobra outdrive with a few minor adjustment everything worked as advertised you will have to place the cobra motor fly wheel cover onto the mercruiser and you will also have to place the cobra flywheel on the mercruiser then line it up and slide it in
as far as the jb weld is concerned i would do a temp fix on the valley with brake free to clean it let it dry then use liquid form of jb weld let it dry then get a putty called maxium steel like i stated earlier and place it over the jb weld after dry and let it dry then you should be good to go putty dry's extremely fast

 

[glasstream86]

Re: omc 4.3 block question

you will have to stick with the same size as far as v-6 or whatever and try to stay around the same horsepower

 

[boatproblem]

Re: omc 4.3 block question

what i am wondering is, are the couplers on the 4.3 cobra drive the same between 86-89. we have a 85 motor on a 86 cobra drive and are concerned that the couplers wont fit on a later say 1988 4.3.

 

[glasstream86]

Re: omc 4.3 block question

not real sure i am sure someone on here should know