3.0 140hp compatibility/interchangeability

[John MD]

Got a 88 OMC 3.0 140hp I/O Cobra.

She has a cracked block and I am looking to replace the engine.

I purchased what was advertised as a 80-90 model mercruiser 3.0. It was cheap and the engine is good...but once I ran the serial at home its a 73 or so. The leaded fuel sticker should have been a sign from God...but oh well.

Question. Will this engine work for a swap, or is the head port design different? The boat is at a shop 2 hours away. The 73 3.0 here. Not looking to pull and swap heads if at all possible.

Also....anyone know how the 3.0L 140hp inline 4 is broken out over its long run in regards to differences to just the engine...not accessories....whether it is in OMC, Mercruiser, or Volvo?

Thanks for any assistance.

Best Regards,
John M

 

[Haut Medoc]

Re: 3.0 140hp compatibility/interchangeability

Welcome to iboats....
It should work just fine, the GM 140 (3.0) is still the same engine as it was 40 years ago.....
The only thing that makes it Merc, Volvo, OMC are the bolt ons.....​

 

[oops!]

Re: 3.0 140hp compatibility/interchangeability

its a work horse !

they use motors on all the big housrboats on the shuswap lakes.

just check the comp before you drop it in.

oops

 

[Bondo]

Re: 3.0 140hp compatibility/interchangeability

Ayuh,......

Pretty much regardless of Vintage,+ Port Shape,....
Just bolt it together,+ Go......

Any HP gains or losses would be Squat.....

 

[John MD]

Re: 3.0 140hp compatibility/interchangeability

Thanks guys!

I appreciate the quick responses.

Best Regards,
John M

 

[rodbolt]

Re: 3.0 140hp compatibility/interchangeability

are you sure its a 73 3.0? I dont think the 3.0 was in production until about 80 or 81.
yes there were at least 4 intake/exhaust port combinations toss in the 2.5 and it goes to about 6 or 7.
easiest way to tell is the 2.5 used a simple iron pully on the crank snout and the 3.0 used a rubber mounted harmonic balancer.
there is another way to tell by looking at the stbd side if the engine block where the head meets the block but I cant remember offhand.
the 3.0 was also made in a 1 piece and 2 piece crnk seak designs.
if your block is cracked odds are high your manifold is crcked as well.
you can buy a 3.0 long block complete less exhaust for about 2000 dollars brand new.
the 2 piece and 1 piece seal flywheels and couplers wont interchange, unless the late style 3 bolt triangle coupler is used.
but the flywheels wont period.
so make a very very careful comparison of the crankshafts,flywheel diameters and head intake exhaust port configurations or bad things may happen.
and have your manifold presure tested at a minimum and maybe just toss the riser for good luck.

 

[John MD]

Re: 3.0 140hp compatibility/interchangeability

She has a harmonic balancer on the front. She essentially looks identical to this picture I found on the the web:

I already have a good replacement exhaust/intake manifold. That's where we started. And we haven't confirmed crack in the old block into the cyls. Just know its cracked on the side, and the old manifold was cracked, so going to pull the old engine for tear down and repair for a spare and run with this one for now.

I am under the impression that the crank bolt pattern changed around 1990 or so in regards to the flywheel. I.E. Got to mate some a new flywheel on the new blocks to adapt to OMC. Some other minor change as well. And the intake and/or exhaust ports changed on the head over the years. My major concern is mating the late 80s vintage OMC manifold to the ports. Don't want a manifold leak.

Thanks for the heads up.

Best Regards,
John M

 

[wire2]

Re: 3.0 140hp compatibility/interchangeability

are you sure its a 73 3.0? I dont think the 3.0 was in production until about 80 or 81.
.....

I bought a new 17' Glastron in '74, it had a 140 hp Merc I/O that was listed as 180 cu inches, which I believe is ~3.0, it looked similar to the picture above.

 

[Don S]

Re: 3.0 140hp compatibility/interchangeability

They have the 140 with the dampner in the 73 parts manual.
http://epc.brp.com/login.aspx?ReturnUrl=/default.aspx?brands=ej&lang=E&brands=ej&lang=E

 

[HT32BSX115]

Re: 3.0 140hp compatibility/interchangeability

Wow,

I went to that BRP parts site and they still list the King Cobra 7.5L manifolds, coupler and other "scarce" stuff... When I added them to my "Pick List" it just added them with no error messages.

I wonder if they're finally going to have a source for previously unavailable stuff?