OMC 4.3 Motor Swap

Q

qcarlson

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I have a 1985 4.3 ltr OMC good engine and a blown 1987 OMC 4.3 that i would like to replace the 87 with the 85 the only difference i can find is that the flywheel is bigger on the 87. I think the assembly for the out drive will bolt onto the smaller flywheel and if I switch out the wireing harness form the 87 and move it to the 85 I should be good. Am I missing something here??? thanks the 85 is a complete motor...
 
Bondo

Bondo

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Re: OMC 4.3 Motor Swap

qcarlson said:
I have a 1985 4.3 ltr OMC good engine and a blown 1987 OMC 4.3 that i would like to replace the 87 with the 85 the only difference i can find is that the flywheel is bigger on the 87. I think the assembly for the out drive will bolt onto the smaller flywheel and if I switch out the wireing harness form the 87 and move it to the 85 I should be good. Am I missing something here??? thanks the 85 is a complete motor...
Click to expand...

Ayuh,.... Welcome Aboard,... Did ya notice the flywheel Bolt pattern is also different,..??

they don't make the part you need to make that work in an OMC...
 
Q

qcarlson

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Re: OMC 4.3 Motor Swap

No I didn't notice that... I thought it was the same but no dice huh...
 
Q

qcarlson

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Re: OMC 4.3 Motor Swap

qcarlson said:
No I didn't notice that... I thought it was the same but no dice huh...
Click to expand...
So i went to the motor and the assembly hub does have a different bolt pattern. so it wont bolt right on but this motor was built by OMC so i am a little confused by your statement "they don't make the part you need to make that work in an OMC..."??
 
Bondo

Bondo

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Re: OMC 4.3 Motor Swap

qcarlson said:
So i went to the motor and the assembly hub does have a different bolt pattern. so it wont bolt right on but this motor was built by OMC so i am a little confused by your statement "they don't make the part you need to make that work in an OMC..."??
Click to expand...

Ayuh,.... Both motors were built by Chevy,....

Chevy changed the crankshaft bolt pattern in '86....

There is No coupler adapter to do what ya wanta do....

Ya need another 2 piece rear main motor...
 
Q

qcarlson

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Re: OMC 4.3 Motor Swap

ok thanks i just want to clarify one thing 86 and newer with mechanical fuel pump will work correct!
 
Howard Sterndrive

Howard Sterndrive

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Re: OMC 4.3 Motor Swap

you need the 4.3 that was made from mid 1985 to mid 1986. Kinda rare because there was only a couple of runs and then they switched to the different style crank.
Any 4.3 made after approx Feb 1986 is a no-go. doesn't matter what sort of fuel pump is on a 1987 or 1988 etc, they will not work for you.
 
Q

qcarlson

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Re: OMC 4.3 Motor Swap

Howard Sterndrive said:
you need the 4.3 that was made from mid 1985 to mid 1986. Kinda rare because there was only a couple of runs and then they switched to the different style crank.
Any 4.3 made after approx Feb 1986 is a no-go. doesn't matter what sort of fuel pump is on a 1987 or 1988 etc, they will not work for you.
Click to expand...

I think there is some confusion here I am replacing a 1987 OMC 4.3 Liter with a cobra out drive. I have a good 1985 Motor this obviously wont fit. every thing I have read on here says a 86-91 4.3 will work or 91+ with a mechanical fuel pump...
Thanks again
 
Howard Sterndrive

Howard Sterndrive

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Re: OMC 4.3 Motor Swap

glad you posted back.
I had it backwards and suspect Bond-o did too.

You can use the 1985 motor! You just need the correct coupler.
0983902 COUPLING ASSY. is the earlier Cobra coupler used on early 1986 units with the carry over 1985 style 4.3
(Omc did use some of those early crank style V6's and V8's with Cobras, and the 3.0L didn't make the crankshaft change until late 89, so a coupler does exist- available at any Evinrude dealer for around $250)
and you might need a starter motor if the 85 motor doesn't have one on it

once the right coupler is on, everything else should bolt up just fine.
sorry we almost sent you on a goose chase
 
Q

qcarlson

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Re: OMC 4.3 Motor Swap

Howard Sterndrive said:
glad you posted back.
I had it backwards and suspect Bond-o did too.

You can use the 1985 motor! You just need the correct coupler.
0983902 COUPLING ASSY. is the earlier Cobra coupler used on early 1986 units with the carry over 1985 style 4.3
(Omc did use some of those early crank style V6's and V8's with Cobras, and the 3.0L didn't make the crankshaft change until late 89, so a coupler does exist- available at any Evinrude dealer for around $250)
and you might need a starter motor if the 85 motor doesn't have one on it

once the right coupler is on, everything else should bolt up just fine.
sorry we almost sent you on a goose chase
Click to expand...

Thanks you guys are great....
 
O

Ochoa

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Re: OMC 4.3 Motor Swap

qcarlson said:
ok thanks i just want to clarify one thing 86 and newer with mechanical fuel pump will work correct!
Click to expand...

Im in a similar situation.

I have a 1988 sunbird with a 1988 4.3 L V6 OMC Cobra. The block is cracked. All the externals are ok. I have the block stripped down and am searching for a used block. Is this statement true for my situation? Or, do you know what blocks I can use out of an automobile? late 80's GM cars? Jimmy, S10, Blazer?

I have been told I need to use the cam out of my blown block, and I will need to change all the "freeze plugs". Anything else?

Thanks!

(My new thread on this topic)
http://forums.iboats.com/showthread.php?t=584005
 
RichardNaugle

RichardNaugle

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Re: OMC 4.3 Motor Swap

would the same solution work for a 1989 4.3l? this is what mine is and i'm looking for replacement options
 
O

Ochoa

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Re: OMC 4.3 Motor Swap

As far as ive been able to tell, Im looking for a 1988-1991 GM 4.3L V6 out of Jimmy or a pickup or GM van or something like that... Let me know if you find anything else out about this, Im going to the junk yard Sunday to search...

Thanks!
 
Q

qcarlson

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Messages
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Re: OMC 4.3 Motor Swap

I found a 1986 out of a Bayliner and just had to change the coupler to the outdrive.
 
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