Mercruiser carb on OMC manifold

[Mystic Dragon]

Hey guys,

I got my manifold installed (remember a Merc 2.5L, OMC outdrive and a riser problem). Riser fits fine now however the Mercarb 2bbl will not fit on the manifold.

Aren't Mercarbs Holleys and OMC Rochesters? I know where I can get an adapter plate but just want to make sure this will work.

Any help will be greatly appreciated.

 

[Don S]

Re: Mercruiser carb on OMC manifold

Aren't Mercarbs Holleys and OMC Rochesters?

A Mercarb is a Merrcury Marine carb (hence the name) it is built similar to a Rochester and the bolt pattern for the base is slightly different than a Rochester.. Has nothihg to do with Holley.

 

[Mystic Dragon]

Re: Mercruiser carb on OMC manifold

Thanks Don. Is there any way to adapt the Mercarb to the OMC manifold? I thought that the patterns were the same but they are slightly different.

 

[Bondo]

Re: Mercruiser carb on OMC manifold

Why not just put the Right carb on,..??....

I might be Wrong,....
But, I believe the Linkages are also Different......
As well as the Lines....

 

[Mystic Dragon]

Re: Mercruiser carb on OMC manifold

Bondo, I have a perfectly good Mercarb and I have just spent $680.00 on a manifold, riser, flapper and a trim motor. I am trying to lower my costs and another $200.00 just isn't in the cards.

There isn't too much difference between the two as far as the mount pattern so it is just a mounting issue and not a performance issue with one difference. I have already hooked up the electronic choke to the Mercarb and would prefer not hiving to go back to the manual one.

Right now I have a Mercrusier 2.5L block with an OMC 3.0 bellhousing, coupler and wiring harness with an OMC manifold and riser. I need to get the Mercarb on it to avoid having to buy another one as well as not revert the choke back to manual.

I hope this helps explain my dilemma. Any ideas?

Oh, and the linkage I can deal with. I just retrofit the old linkage to the new carb its fits perfectly on the manifold.

 

[Bondo]

Re: Mercruiser carb on OMC manifold

Well,....... I consider Myself to be 1 of the Kings of Creative Engineering,.......
I Know I cause Don to Cringe on occasion.....

You're on your Own trying to do what you want to Do.....
Nobody builds Adapters to do it.....

Btw,.... I've Never seen a boat with a Manual Choke.....Not even an OMC.....

If you're only lacking 1/2 a bolt Hole,.... Maybe you could Grind it Out,......
I Donno,... I can't See it.......

I'd Think that if you're any farther away than That,.....
It's going to cause More Problems Later.......

Good Luck....

 

[Mystic Dragon]

Re: Mercruiser carb on OMC manifold

Thansk Bondo. I think that I may have to compare the two more closely and see what I can do. The guy at the marina says that the holes are a quarter inch off so maybe spreading them will work.

I was hoping that they made an adapter. By the way, I think I mispoke. The manual choke is probably done by vacuum pressure instead of the electric one on the Mercarb, so I guess it is auto but just different.

 

[Bondo]

Re: Mercruiser carb on OMC manifold

You'll also have to make SURE that the carb. Bases are the Same,....
There could be Vacuum ports that need to be addressed,+ you Don't want any Lip or Anything to interfere with the Smoothness of the Airflow.....

I Still think you should Find a Carb that Fits.........

If the Bolt Holes are Off that Far,.... I gotta believe that there's More that Doesn't line up.....

 

[Reel Poor]

Re: Mercruiser carb on OMC manifold

If your even going to attempt a modigfication be sure to check the throttle plate bore size. They come in different sizes. If the Mercarb is larger than the bore in the intake the throttle plates may hit the edges of the manifold. You could compare them with a baseplate gasket thats not going to fit either.

Get the right carb. Usually one marine modification requires another and another and another and ..........Well you already know that from using the OMC manifold on the Mercruiser. :^

 

[whywhyzed]

Re: Mercruiser carb on OMC manifold

I sold 2 or 3 good OMC 4 banger carbs on eBay last year... they went for $40 to $60 each. couldn't make an adapter for that.

 

[Mystic Dragon]

Re: Mercruiser carb on OMC manifold

Thanks guys! Yeah I think that I am going to see about having the marina mechanic (he's real good) rebuild the old carb off of the 3.0 shell I have and use that. That way I know things will line up. I will just have to disconect the electric choke. It really shoouldn't effect anything.

Thanks for all of your help. Hopefully I will get this thing running soon. d

 

[Bondo]

Re: Mercruiser carb on OMC manifold

I think that I am going to see about having the marina mechanic (he's real good) rebuild the old carb off of the 3.0 shell I have and use that.

Have him Fix, or Replace that Choke while he's at it......

 

[Mystic Dragon]

Re: Mercruiser carb on OMC manifold

Will do, Bondo! Thanks.

 

[CobiaXL]

Re: Mercruiser carb on OMC manifold

Make your own adapter plate.Only parts needed is 1inch thick chunk of aluminum, (2) one inch hole saws (wood or metal)and a drill.
I took a merc exhaust manifold and used on my 3.0 140hp gm omc motor.Used 2bbl rochester from omc.I took a 1 inch think chunk of aluminum and cut 2 1 inch holes for butterflies to clear.Drilled holed to match merc bolt pattern,then added studs on other side to match rochester 2bbl bolt pattern,works great!!
As for the choke,i deleted it...Who boats in the cold?

 

[cr2k]

Re: Mercruiser carb on OMC manifold

YES it does have something to do with Holleys as in Holley crap it wont fit.

 

[Bondo]

Re: Mercruiser carb on OMC manifold

January 5th, 2007, 03:26 PM

Ayuh,... CobiaXL,.. Archives are for Learnin',.. Not posting too...
I'd think the OP probably has this issue Fixed, sometime over the last 3 Years...

 

[Bob_VT]

Re: Mercruiser carb on OMC manifold

Thank you gentleman for answering this OLDER thread!! I think with a viable answer I can now close it!!

Closed