460 King Cobra Swap To 454

[txbluenoser]

I recently purchased a 1987 Bayliner 2850 Contessa Command Bridge. It is a project boat. It has an OMC 460 King Cobra in it that is completely shot. I'm told the outdrive is okay. I've been looking at the posts online for the 460 and I've been looking for parts and I've concluded that there is no way I'm throwing money into the 460. The engines cooling system is shot, the block is shot, starter and alternator don't look good. It's just too much money to hunt down everthing for the 460. The boat is in salt water year around.

Okay, my question is, how hard is it to replace the 460 with a 454 mercruiser but keep the OMC king Cobra outdrive? Is it as simple as replacing the bell housing and coupler on the 454 with the OMC 454 parts? (work out the exhaust, engine wiring and hydraulics too) Has anyone ever done this? My thoughts were to first replace the engine and then the outdrive later (Bravo 1 maybe) if the OMC king cobra dies (or is not working at all).

Thanks,

Jake

 

[HT32BSX115]

Re: 460 King Cobra Swap To 454

Okay, my question is, how hard is it to replace the 460 with a 454 mercruiser but keep the OMC king Cobra outdrive?

Hi Jake,

It's probably do-able....

You'd need to find new manifolds, risers a nearly non-existent flywheel housing , and figure out a way to make the shift assist module to work with the Mercruiser ignition system.



The problem is that you'll still have an unknown condition King Cobra drive that has all it's own unique problems.


Your best bet would be to part the whole mess out and find a Bravo I/II/II drive and engine and swap the whole mess out.

(Believe me I asked all those questions before I did it!!!)


I parted everything out and got a little more than $3000 by the time I sold all the OMC junk left over....


For a boat that big I would suggest a Bravo III. That's a big heavy boat.....Get a 2.00:1 or 2.20:1 ratio drive.


I am very happy with the Bravo III in my 21' boat. I got a 1.81:1 drive and can swing 26p props but my boat probably weighs HALF what your boats weighs!


If the King Kobra drive is in good usable condition, just sell it. The Big Cobras are getting VERY scarce and are somewhat in demand.





Cheers,


Rick

 

[txbluenoser]

Re: 460 King Cobra Swap To 454

If I can find a good donor boat, that is the way I will go. I've been looking around but have not found one. There are a lot of 454 Mercs around for sale at very reasonable prices.

I thought I'd be able to keep the merc exhaust manifolds and risers. What would be the reason to change them? I was actually considering for a while using those 460 - 454 adapters to put 454 risers on a 460 but came to my senses.

How does the shift assist module work? Does it idle the engine down? IS it mechanical or electrical?

Thanks for your post Rick.

Jake

 

[HT32BSX115]

Re: 460 King Cobra Swap To 454

It's an electrical device.


It's best described as an ignition "pulser" It causes the engine to "lope" to produce torque (reduction) pulses. With the reduction in torque on the shift "dogs" you can easily overcome the approx 5 degree undercut holding them together. Without an abrupt reduction in torque it's VERY hard to pull them apart.


It's not a great system. but adjusted correctly, it DOES work. OMC pretty much eliminated it later on by going to a "cone" clutch system which was then adopted and improved by Volvo when they bought the whole "farm" from OMC in the mid to late 90's.

The OMC 454 was never bolted to a Dog clutch Cobra....when they came out with the 454, OMC had a Cone Clutch drive ready to go in front of it.


You will be able to put a Mercruiser Bravo transom in there with no problem. You'll only need to drill 2 additional holes for the extra 2 studs in the Merc transom mount.....and you'll need to slightly relocate the side engine mounts.

Be sure to check carefully for water intrusion and/or rot in the transom and engine mount stringers.

I was actually considering for a while using those 460 - 454 adapters to put 454 risers on a 460 but came to my senses.

Yeah me too!! I came to my senses too!! You'd still be stuck with that non-existent coupler also. There is a way to machine the flywheel and use a Volvo Penta coupler but after you see that you still have a King Cobra drive, it all falls apart.

There are parts in the (big) King Cobra dog-clutch drive that are just NOT available any more. A vertical drive shaft comes to mind.

Most or all of the parts for the smaller "dogs" are still available but some parts for the big one are either "new-old-stock" or junk yard cannibalized parts.

I'm glad I didn't try to keep mine.....

Here's a couple of pictures for comparison.

Before:

After:

It wasn't all that hard a swap.

You need everything from the donor boat. I also replaced my shifter with a new Teleflex CH1700. It REALLY works nice. You can use your old steering cable. I also used the complete electrical harness from the donor boat because it had a couple of extra wires and was 10 years newer.

I also got the gages but my gages were newer and in better shape.


Now I want a 502MAG MPI engine..... you can never have enough power!

If you're going to run in salt, add closed cooling too if the engine isn't too old or has already been living in salt.....

Good luck finding a donor!


Rick

 

[txbluenoser]

Re: 460 King Cobra Swap To 454

Hey thanks Rick. I'm going to concentrate on finding a donar boat now. I think its just best. It will add a lot of value to the boat if I ever decide to sell and buy another. I'm not in a hugh rush, cause the interior and exterior of the boat is a massive project in itself that will give me plenty of time to find the right donor. Either Merc Bravo 3 or Volvo Penta DP. Thanks again.

Jake

 

[HT32BSX115]

Re: 460 King Cobra Swap To 454

I looked for either a BBC/Merc Bravo and BBC/Volvo.
I found (and continue to find) several Mercruiser engines and drives locally on Craigslist.

I never did find a complete Volvo Penta BBC DPS etc engine and drive. They're probably out there but just not as plentiful.

Have a look on ebay too. you'll find a multitude of drives, engines, parts etc... I paid $5k for a complete 1997 454/Bravo III removed from a (wind damaged)1998 Bayliner 24' cuddy. It had 122 (freshwater) hrs on the hr meter.....and I bought it from the original owner.

Ultimately you'll want something similar as long as you can verify what the owner claims.


Good luck,



Rick

 

[txbluenoser]

Re: 460 King Cobra Swap To 454

How many hours on the gear should I try and stay under? What is the useful life typically?

Jake

 

[HT32BSX115]

Re: 460 King Cobra Swap To 454

That could be "up in the air" ....because you'll have a hard time verifying that the previous owner took good care of the equipment.

These engines can easily go 2000 hours or more if operated frequently, and maintained properly. The drives can go about as long too.

Poorly maintained they can be "worn out" easily in a few short years...

Mine was 8 or 9 years old. The boat was used gently (except when the tree fell on it!!!) and mostly kept inside most of it's life and I could tell. It was obvious it was not used in salt.

Depending on what you want to spend, You could get a new or new old-stock drive from ebay for around $3000-4000 and find a used gimbal mount. Then locate a cracked block engine that you could either "long-block" or rebuild etc...but you would need to find all the accessories trim pump, wiring, etc....

The best way would be to find a damaged boat (hopefully not too damaged!!).... the advantage here is that you get all the accessories, hardware, controls, gages, plumbing, exhaust etc....


I wanted at least 300hp and I almost bought a 2003 Closed Cooled Mercruiser 300hp 5.7L MAG MPI with a Bravo I drive. It had 400 hrs on it but had been used in salt all it's life but was not ever stored in the water. The owner wanted $7500 for it and turn down $6000 cash. I was about to offer $6500 when the 97 454/BIII showed up. (the dealer that was trying to sell it for him told me he would probably take $7000)


A couple of years ago I found a 2005 or 2006 496 MAG MPI + Bravo III on Craigslist locally for $8000. I think it had something like 80hrs since new on it and it was the 425hp model....

I wish I had gotten it!!!


If I had your boat and was looking to repower I wouldn't consider anything smaller than a carbed 454 and would lean towards an EFI 454/502 or 496 2000 or newer...and on a boat that big I would only look for Bravo III's (or Duo-props)

 

[txbluenoser]

Re: 460 King Cobra Swap To 454

Hey Rick, Thanks for all your comments. They have been very helpful.

One thing that keeps me coming back to keeping the OMC KC drive is that my boat has a command bridge and hence 2 sets of controls. I've not had a chance to look at how they work together, or how one overides the other.

My next question to a complete swap out is what consideration I need to make for the dual controls and what is special about them?

Thanks,

Jake

 

[HT32BSX115]

Re: 460 King Cobra Swap To 454

Jake,

Just food for thought but you can pick up a Ford 460 truck engine pretty cheaply and marinize it. (Assuming the drive is in good shape.)

If you go ahead with the swap I have the wiring diagrams for the dual control setup for the OMC.

His problem is not just the drive. It will also be the exhaust manifolds, risers, and coupler. Those parts are for the most part no longer available.


The actual engine is the easy part. No problem there....Several rebuilders quoted me around $1995.00 for a long block.
I wouldn't wish an OMC 460 King Cobra on my worst enemy. (unless I had one I wanted to sell!!!)

My next question to a complete swap out is what consideration I need to make for the dual controls and what is special about them?

I haven't done a dual control system. My guess is that you would replace both quadrants and use a dual station control system if the current ones wouldn't accept Mercury style cables. (I'll bet they do)

Here's a Teleflex example http://www.teleflex.ru/upload/files/catalog/kdu/Connection kits.pdf

 

[txbluenoser]

Re: 460 King Cobra Swap To 454

My exhaust manilfolds and risers are shot also. Everyhting on the engine is pretty much toast.

So a long block is 2,000
Manifolds and Risers 2,000
Water pump, starter, misc 1,000

5,000 is pretty much the minimum I could do to rebuild the motor, and like Rick says, then there is the coupler which is imposible to find if it ever goes, and 2,000 to replace exaust system if it ever goes again. And the fact that having the 460 will devalue the boat somewhat when I decide to sell it.

So buying a wind damaged donor boat for 6,000 and getting much newer gear all around makes sense. I could likey sell of the kc outdrive to reduce that cost. I really want a dual prop drive bravo 3 or Volvo for her in the long run anyway. Boat weighs in a 6000lbs. She'll need the thrust.

I've been around and around on this. I still may try just buying a 454 mercruiser and making the mods. I could do that for under $2,000. The bell housing are out there for 100 bucks and couplers are available too. But I still don't know the condition of my outdrive. It's been in salt water a long time not used. It does have anodes on it so it might be okay. The king cobra drive is a good one if adjusted properly. So maybe I could sike 2k in a 454 a be good for a long time. The previous owner told me the out drive was rebuild shortly before he blew the moter. That was 6 years ago though.


Jake

 

[HT32BSX115]

Re: 460 King Cobra Swap To 454

The previous owner told me the out drive was rebuild shortly before he blew the moter. That was 6 years ago though.

That may not tell you much if it sat in salt water for 6 years....

You'll should probably drain the drive oil and have a very close look at the U-joints, gimbal bearing etc..... It's very easy to say the drive was "rebuilt" 6 years ago.....(6 yrs is a long time for anything to "sit" in salt water)


Good luck!



Rick