4.3 Mercruiser rebuild. Technical engine info.

[BMV1]

Hey all! I'd like to get some info and options for this little project that I am starting.

The engine I have is a 4.3 Mercruiser. From the research that I have done, it seems to be a 1989-90 Buick. The CASTING # is 10105867. The research that this is pointing me to is a 1989-90 Buick block. I believe the block is cracked. I have it taken down to the crank, cam, and pistons. But in my inspection of the block, I found a fracture.

The first part of my question is, do you have anywhere that I can do more research on the casting number, or do you have knowledge weather I am correct on the year?

Part two, assuming that it is a 1989-90 Buick, would I simply be able to find a block at a salvage yard out of one of the cars that it was in? If not, is there a difference in the "marine" vs the "road" version if the cast numbers are matching?

Here is the PDF of some of the research that I have done. My casting number is the first one o the list if you are clicking on it. http://www.enginepartswarehouse.com/enginecatalog/GENERALMOTORS.PDF

Thank you in advance!

 

[tpenfield]

:welcome: . . . to iBoats.

Not entirely specific to Buick, but yes, the engines are made from a GM base engine, with marine fuel, ignition, electrical, and cooling systems added. You should be able to find a suitable block from a variety of GM vehicles with that same casting #. There are probably other casting #'s that will work for you as well.

You should be able to do the same for the cylinder heads, if needed. The cam from the original engine would be good to use on the donor engine, as the cam in the 'marine' engine will have less overlap than what you may find in an automotive engine.

 

[BMV1]

The cam from the original engine would be good to use on the donor engine, as the cam in the 'marine' engine will have less overlap than what you may find in an automotive engine.

Awesome. Good to know about the cam. I am hoping that I can reuse the crank, and the cam, but it is totally seized up, so no telling what will be usable.

As a side note. Generally when I do these types of engine builds, I take the block in to a machine shop. Do you know, or have an idea about machining and how much bore is too much on a marine engine? I know these things run high rpm.

 

[Bondo]

Ayuh,.... Welcome Aboard,.... Donno 'bout anything Buick, they may have used it I guess,... yer motor is a Chevy pickup motor,....

It's a Chevy based motor,....

As for replacement, ya can't go wrong buyin' a long block replacement crate motor for a Chevy pickup of the appropriate vintage as yer ole motor,....
'n the Merc serial number is way more important than the castin' numbers yer searchin',...

 

[Lou C]

No not Buick. These engines date from when each GM division made their own engines. The 4.3 in Merc, Volvo or OMC boats is really just part of the Chevrolet small block family, it is a 5.7 with 2 cyls removed. So the bore and stroke are identical to the 5.7. You'd need a block/heads out of a GM midsize truck like a Chevy S10, Blazer etc. They were also used in some full size Chevrolets in taxi service.
​The Buick was actually used in some OMC applications but a very long time ago. They were 3.8 liters or 231 cu in. Used in midsize Buicks and Oldsmobiles, and in Jeep CJs before they switched to the AMC sourced 4.2 inline six.
​The Chevrolet engines all had the distributor in the rear, the Buicks had it up front.

 

[Scott Danforth]

that casting number is a 1986-1992 Chevrolet 4.3. it was NEVER in a Buick. Buicks of the era used the 3.8 liter Buick motor, which became the 3800 then the 3800 series II. The Regal is the only GM A/G body that could have received the 4.3, and the only two motors that were in them were the 3.8liter buick and the 5.0 chevrolet

here is some reading material on the 4.3 http://forums.iboats.com/forum/engi...history-of-the-4-3-liter-with-casting-numbers

 

[BMV1]

Thanks for all the info guys! So when I get to shopping for an engine, can someone tell me if this is a carb or a throttle body? Someone at some point had started to tear down this engine and had no *blanking* clue what they were doing, so half of the pieces for the top end are MIA. I suppose I could convert the tbi, but was hoping someone could tell me if the engine I'll be shopping for was TBI or carb.

 

[harleyman1975]

I think a carb is going to be the easiest way to go.

 

[Bondo]

I suppose I could convert the tbi, but was hoping someone could tell me if the engine I'll be shopping for was TBI or carb.

Ayuh,.... You've told Us Nothin' 'bout yer motor,....

Normally, ya buy a long block crate motor, then swap over all the accessories off yer motor, onto the long block crate motor,.....

Crate motors are just Long Blocks,.... No accessories,... No carb, No efi, just a long block,....

 

[BMV1]

Sorry, the info that I have on the engine is the casting numbers. The serial plate is gone. I see where it was at one point but no longer. The boat it was in is an '89 thunder craft bow rider. When I got the thing, all the wires and harnesses had been removed, someone had pulled half the bolts off the intake manifold, the carb/injector is MIA, and someone had taken off both valve covers, and one side of the rocker arms (??????). So, now everyone has as much info on it as I do lol. As far as the doner engine goes, i like pick'n'pull places. I've called a few around where I live and I can get the whole engine for around 200, +/- depending on whether or not I go with a TBI or carb. So, I guess what I'm really asking is when I go to buy one of these salvage engines for donar parts, does anyone have any idea if carb or tbi would be a better idea, or if a carb is fine?

 

[Rick Stephens]

You will not be able to get anything more than the long block from a pick and pull. Everything from fuel pump, to carb, to water pump, to ignition is marine rated and not automotive. Just to be REALLY clear, you cannot use the carburetor off an automotive pull. IMHO, you are wasting your money to go buy a donor engine out of a pickup, van or car, for the parts. The only useful parts would be the long block.

It would be useful to list everything you need. Or conversely, everything you have. Take pictures and post those would be great help.

Your motor would have come from the factory most likely with either a 2 barrel Mercarb or a 4 barrel Rochester. You should be able to tell by looking at the intake. I don't believe Merc was shipping TBI with the 4.3L in '89. A wild guess would be you have Thunderbolt IV ignition.

 

[netting one]

Dont want to dirty the water but did this already. Things to watch out for: make sure of mechanical fuel pump is open on the block, also the motor we picked up had a balance shaft in it, got rid of that. The oil pan bolts were different on the boat oil pan so we had to drill and tap the block. I think that was it but after all it runs ok!

 

[Bondo]

. When I got the thing, all the wires and harnesses had been removed, someone had pulled half the bolts off the intake manifold, the carb/injector is MIA, and someone had taken off both valve covers, and one side of the rocker arms (??????). So, now everyone has as much info on it as I do lol.

Ayuh,.... Welcome Aboard,.... A junkyard motor isn't gonna help you, at All,.....

Only the Long Block will interchange 'tween a Marine motor, 'n an automotive motor,....
Everything bolted to the Long Block that'll make it a runnin' bobtail boat motor is Different than a car motor,...

 

[BMV1]

It would be useful to list everything you need. Or conversely, everything you have.

Okay, I dug around in the boat, and took pictures, but they are not wanting to load, so the list is as follows best I can tell.

Here is what I am sure I need:
-One exaust manifold (have one, need the other)
-Block
-Carb
-Fuel pump
-Starter
-New pistons
-Lifters
-Valve caps
-Oil pump
-Oil pan

This is just based on the tear down. The boat is in really rough shape and I am doing this as a project. The boat was not winterized and water got in and cracked the block. The boat was then left to rot, and I have no idea how long it has been sitting with the water in the engine.

As to what I have,
-Intake manifold
-Cylinder heads
-Head compnents
-Water pump
-Cam
-Crank
-Timing chain and pully
-Balancer


I think most of the wiring is still intact, but that isnt a concern until I know if I can get this engine "rebuilt". I have the original engine torn down to the block now. My initial idea was to find a salvage engine, tear down to the block, use the "guts" from the old engine in the "new" block, and buy whatever else I would need along the way new or refurbished. My reasoning behind a salvage yard is that the one I normally go to charges refundable core fee of $50. So, if I buy the "new" engine, and return the old engine block with heads, a cam, and a crank, I get the core fee back. In essence I would be getting the block for $150 +/-.

Most of the important components look like they can be used after a quick trip to the machine shop. The smaller items do not worry me as much, because I can buy them as needed from a reputable parts dealer. That is, as long as I know what engine block I am dealing with. So, is everyone in consensus that it is an 89 ish Chevy?

All that said, if I do the salvage yard route, generally on a rebuild I have the cylinders polished. What bore ratio should I stay under?

 

[Bondo]

generally on a rebuild I have the cylinders polished. What bore ratio should I stay under?

Ayuh,.... SoP for rebuildin' a motor is to overbore .030", 'n install new fitted pistons,....

.040", 'n .060" are options if the bores don't clean up perfectly at .030",.....
.040 ain't to bad, but if a block needs .060 to clean up, I call it scrap iron,....

Yer plan don't sound reliable at all to me,....

My initial idea was to find a salvage engine, tear down to the block, use the "guts" from the old engine in the "new" block,

That's pretty much guaranteed to fail,...
The Guts of either block should stay with the same block, unless line-bored,...

 

[tpenfield]

Usually, you would take the block along with the guts (aka rotating assembly) all together as one, if you were considering it at all. Fitting pistons from one engine into another block without machining (over boring) is like wearing someone else's underwear . . . it will never feel right

 

[Rick Stephens]

Right way: get your long block from a pickup. Do what it takes to rebuild it correctly. Boats are funny, they run at full load from idle through top RPM. You can't cut corners. There are tons of differences in blocks, valve train (flat tappet, roller), heads, intakes, pan, front timing cover, balance shaft. You need to know what your goals are before buying anything. You can stay all '89, if you go newer and go all Vortec (post 96), thateans changing a bunch of stuff. Otherwise, stay pre-balance shaft and you're golden.