Mercruiser 4.3 block

rob 135

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I have a 86 Chaparral 195 xls for my project boat. When I got it had been neglected for awhile. Bad interior and soft floor. The previous owner had a new reman 4.3 mercruiser installed but never fired it up , never even put oil in it. Well it was stuck when I got it , took apart and cylinders have some bad rust pits from sitting water and animal urine , valves are rust and stuck open . so long block not much good any more. I was just going to get used truck engine and do the usual to make it ready for marine use. My problem being I can find newer vortec engines but nothing older. Will my 86 intake and flywheel, and ignition bolt on newer 4.3 ? Which years should I be looking for? Should I put 86 marine cam in ? What do I need to do to get newer engine in and wired correctly? Thanks My normal boat I use is a 79 silverline Comoro tri hull, with 73 ,135 Johnson which I just rebuilt. goes great ,gets boring because nothing ever goes wrong. I like it .
 

Bondo

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My problem being I can find newer vortec engines but nothing older.
Will my 86 intake and flywheel, and ignition bolt on newer 4.3 ?
Which years should I be looking for?
Should I put 86 marine cam in ?

Ayuh,.... Any 4.3l can be retro-fitted into the boat,....

Which pieces are usable, 'n which need adaptin' can be talked 'bout after ya find a motor, 'n Id it's year,....

The intake will work on motors up to '95,...

Yer motor of '86 is a transition year, so it could be a one pc. rear main, or 2 pc,.... 1pc. would be better for you,...
That'll determine whether you can use the flywheel,..

I wouldn't put the old cam in a new motor, just run what's in it,....
 

rob 135

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It is a one piece rear main. I had heard the marine cams were ground different for low end tourqe . So 95 and newer would need different intake also. I been worried about the thunderbolt ignition fitting on newer engine. I want to try and use most all parts I already have instead of searching down new ones. thanks for reply
 

BRG25

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I would be really concerned about a rotted transom on a boat like that. Is this boat even worth putting a new motor in it?
 

rob 135

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Transom is good , I just finished floor and stringers, working on interior now. Then drop whatever I come up with for motor in.
 

Scott Danforth

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96 and newer would be the vortec intake.

the 4.3 went thru many iterations. 2-piece and one-piece crank seal, balance shaft, or non balance shaft, flat tappet vs roller lifters, steel front covers, plastic front covers, vortec heads, non vortec heads, adjustable rockers, non-adjustable rockers.

Brief history of 4.3 (going from memory so I may be off on one or two of the changes)
Introduced in 1985 model year as flat tappet, 2-piece rear main seal replacement to 229 (3.8)
1986 - received 2-piece rear main seal
1987 - received center bolt valve covers and roller cams
1992 - received balance shaft (and different harmonic damper)
1996 - received vortec heads
1999 - crank pilot changed
2000 - non-adjustable rockers, plastic timing cover

your motor was a non-balance shaft motor, so your motor mounts are different than balance shaft motors
your motor is confirmed its a 1-piece crank seal (great news - flywheel & coupler wise)
your motor is a flat tappet cam
your motor is a non-vortec
your motor has adjustable rockers
your motor has a steel front cover

to move over nearly everything, you need to find a 1986 or early 1987 motor.

my recommendation: get a 96-99 S-10 motor, replace the core plugs with brass, and get marine rated head gaskets, get a vortec intake (ebay or other). Then move your exhaust, carb, ignition, water pump, brackets, alternator and starter over to the new motor, then get the solid motor mounts. throwing away your current block, heads, oil pan, harmonic damper, etc.

then again, at that point, I would probably found a V8
 

Rick Stephens

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I also would go with a Vortec. I have now done that install from a pre-Vortec setup, and it is not a huge undertaking. What gets interesting is fuel pump system needs to be electric since the newer blocks don't have a place for a mechanical pump. Which means building a harness and adding a oil pressure switch and solenoid.

The intake is not a big deal, even if you just get a Edelbrock Performa, which is what I did.

Right cam is usually a basic OEM pickup cam. No reason to spend a bunch on a 'marine' cam.

I bought a donor boat with a brand new rebuilt Vortec V6 that had been sitting under a tarp in a rotted out hull without anything except the tarp over the open carburetor. Like yours, it was severely pitted in the cylinders. I was able to break it loose using Marvel Mystery Oil and some muscle and fire it up. Then pulled it down and had it machined. Cost me around $400 for machine work plus pistons and rings and some valve seats as we redid the valves at the same time. Water is not kind. So took a fresh .020 bored rebuild and bored it all .040. Runs like a brand new motor now. Rust like that may not injure the crank or bearings, so check them out before assuming anything. It also may not pit the cylinders enough to make it not re-borable.

Going to a V8 is an option, but the way to do that is find a donor boat with all the dressings for the bigger motor.

Rick
 

rob 135

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What is the difference on the newer motor mounts? I am thinking just like you said S-10 motor and find intake and swap rest of parts.
 

Bondo

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What is the difference on the newer motor mounts?

Ayuh,.... Use the ones ya got,... The holes in the block didn't move,....
 

rob 135

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So for newer vortec engine I would need , 4bbl intake, motor mounts and electric fuel pump wired to oil pressure switch?
 

rob 135

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I just checked around and found a 1999 4.3 from gmc pu with 65k miles for 500 bucks. How will most of my parts interchange to this year? Will thunderbolt distributor fit ?
 

Bondo

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How will most of my parts interchange to this year? Will thunderbolt distributor fit ?

Ayuh,... Everything but the mechanical fuel pump, 'n intake manifold,....
 

rob 135

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Just located another deal on craigslist , 2 complete marine engines . All assecories ,exhaust, ignition , complete . one is 4.3 other is 5.7 both have cracked blocks. 5.7 crack is between freeze plugs ,may be able to weld . but if not there are all my parts for a v8 swap over .Its a 86 5.7 and a 89 4.3. 300 bucks for both engines complete. one person looking at them tomorrow then its me . I said I would buy no questions asked . fingers crossed ,that would be great power plant for Chaparral...
 

Rick Stephens

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Don't forget outdrive gearing changes with the bigger 5.7L. Pretty significantly, at that.

I would not buy a block needed welding and then run it. SBC block is cheaper than the parts it takes to swap it back out when the weld fails.
 
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