OMC 1989 GM 5.7 replacing 1994 Ford EFI 5.8 - need conversion help

[Unlimited 17 San Diego]

Hi All, I have a 1994 Horizon 210 with a bad motor. It's the Ford EFI 5.8 with a OMC / VP Cobra SX. I can get a 1989 OMC cobra GM 5.7 carburetor motor to replace it. Will that fit my mounts? Will the exhaust line up? I would need to adapt a sea water pump to the GM 5.7 but otherwise it's a good mill. I'm trying to get away from the Ford power in this boat.

Any suggestions or comments - no matter how crude - are appreciated!

 

[Scott Danforth]

unbolt all the ford stuff (carb to transom) and replace with GM

simple simple

that also means new transom shield, etc.

however while at it, i would continue replacing until the OMC cobra drive was replaced as well.

 

[Lou C]

That Cobra is the Joint Venture product which is the same is the early SX. No need to replace, but yes the inner transom mount, bell housing and mounts are all different. May also need to replace the Y pipe as the GM exhaust may not line up with the Ford. Check the parts #s on the BRP parts catalog to see if the parts for the GM and Ford models are the same or not. Most of these parts you will have to source used, but they are out there. Other parts that may be different:
engine coupler
shift cable bracket
fuel pump for sure

If you're using an '89 OMC GM engine then you are going back to a carbed engine. They came with Quadrajets or a Rochester 2bbl. Both are fine if the carbs are in good shape. However, these carbs are old now sometimes you need to upgrade to a new Holley or Edelbrock (if it will clear the shift linkage and trim relays on that side), the Holley fits for sure because OMC switched to them in '90 or so.
Ford 5.8:
http://www.crowleymarine.com/johnson-evinrude/parts/42294.cfm
http://www.crowleymarine.com/johnson-evinrude/parts/42291.cfm
http://www.crowleymarine.com/johnson-evinrude/parts/42281.cfm
http://www.crowleymarine.com/johnson-evinrude/parts/42277.cfm

these diagrams have the relevant parts that are on your boat, now you need to go to the section for an 89 Cobra with the 5.7 and look up the same parts and see if the parts numbers are the same or different. This will save you a lot of running around and getting mis-information.