OMC Conversion to Merc

[gas man]

Hello. I know this topic has appeared on this board in the past but I still
have a few questions. I apologize if I missed the answers in previous post
but I'm on a short schedule and need quick answers. I'm thinking of buying a
1986 Grady White with a 4.3L Cobra engine and OMC outdrive with a shifting
issue which I've read (many times) that OMC's are famous for and I have a
mechanic lined up to fix that problem for about $275.

The boat and engine are in great condition for their age. You can tell that
it has been very well maintained and I love the boat but I am leery of the
OMC outdrive with its parts being obsolete and expensive to replace and I
was reading about a SEI Cobra Conversion Kit to a Merc Alpha 1 Gen II. My
questions are as follows:

1. This kit allows converting the OMC outdrive to the Cobra engine that is
already in the boat, correct?
2. The kit is designed to work with an SE116 drive but can also work with an
original Mercruiser Alpha 1 Gen II drive with slight modifications. Should
one be used over the other?
3. Is the Cobra 4.3L a dependable engine or does it have its "issues" also?
A quick response to these questions would be greatly appreciated.
Thanks.
Gas Man

 

[HT32BSX115]

Howdy,


Welcome aboard!

The SEI "conversion" is a pretty good alternative to the Cobra (if your Cobra is "broke")

Not sure if it's cost effective when the Cobra is in good operating condition.

Remembering that OMC has been out of business since 1998, there's nothing really wrong with a good running and correctly adjusted and maintained Cobra drive. You just have to realize that, when it DOES "break", you have to make some decisions on whether it's really worth it to rebuild the drive or replace it with either a rebuilt one or do the conversion to something else.

(I had a 460 King Cobra in my 1987 Four Winns 211 Liberator that I removed completely and replaced with a 1997 Mercruiser 454/Bravo III engine drive package. The 460 had it's own insurmountable problems)

Your engine is a fairly generic GM 4.3L V-6 used by OMC, Mercruiser, Yamaha & Volvo for many years and still used with plenty of repair parts and services available. Certain things like EFI (if equipped) and those "batwing" exhaust manifolds can be problematic.

Check with SEI on what drives their conversion works with. I seem to remember that they work well with their own drive but a Mercruiser Alpha might need some sort of modification to work correctly. Just abut everyone here that has done an SEI conversion has been happy with it.

Also, consider that the exact same boat with a Mercruiser 4.3L/Alpha would be worth much more so don't give too much for the boat!

If the drive has shifting issues, it might be best to assume that the drive is unrepairable and price your offer like you're going to replace the drive. If the clutch dogs have been damaged, the drive will likely need to be rebuilt. That's where it's going to be cost effective to do the SEI conversion.

If it were me, and the boat was VERY nice and not all that expensive, I would be looking for a complete Mercruiser (or Volvo) 4.3L or 5.0L V-8 engine and drive package from a donor boat and just replace the entire mess. To make that cost effective, you would need to get teh boat pretty cheap and get a swinging deal on the new engine and drive.

When I was looking, I found a LOT of used Mercruiser engines and (Alpha/Bravo) drives. (didn't find any Volvos)

Regards,


Rick

 

[Bondo]

Ayuh,..... Welcome Aboard,...... The Kit starts at the OMC gimbel housin', 'n allows the Merc Alpha models to bolt up,...
Pretty much everything forward of that point, stays OMC,....

The SEI drives are carbon copies of the Mercs they compete against, completely interchangeable,....

The only Issue I know of with a OMC 4.3l is the problem Merc also had,....
The batwing, one piece exhaust manifolds,.....
They've Killed millions of motors,....

The Fix is convertin' to traditional center riser manifolds,...

 

[gas man]

Thank you for the information but I'm still a little confused. I'm asking would an SEI outdrive work with the Cobra engine that's in the boat now using the conversion kit? The seller is asking $2200 for boat and trailer. Do you think that is a good price? Thanks again for your time.

 

[Idlespeedonly]

Yes, the SEI swap will work with the "cobra" engine. The engine that is in the boat is not much different than a merc.
The only problem you may have is that the control needs to be reversed. If it cant be reversed it will have to be replaced.
As for the price of the boat, obviously we havent seen it. Look and see what similar boats are selling for in your area.

 

[HT32BSX115]

1. This kit allows converting the OMC outdrive to the Cobra engine that is already in the boat, correct?

YES

2. The kit is designed to work with an SE116 drive but can also work with an original Mercruiser Alpha 1

YES

3. Is the 4.3L a dependable engine

YES

It's difficult to say if ANY 1986 boat with an OMC Cobra in it is worth $2200......maybe if the boat is nice cosmetically and the engine/drive is in good running condition (AND with a proven water test)

But with shifting problems, (which could [worst-case] result in $1500-2000 in repairs) it becomes a boat with NO engine.

There's lots of older nice boats out there with no engine and/or drive that people cannot even give away.


Good luck,


RIck

 

[gas man]

Thanks for all the answers, suggestions, and advice. Greatly appreciated.