OMC Cobra to Volvo Penta DP-S Conversion

[paulcierra26]

I have a 1998 Bayliner with the 460 engine and Cobra (Dog Clutch) Outdrive.

I understand that it is possible to convert a Cobra Outdrive to a Volvo Penta DP-S or SX Drive without to much difficulty.

I know that a new water pump is required to be mounted to the engine , acct the Cobra Water Pump is in the leg.

Marine Parts Express sells the "Transom Adapter Plate Kit" for the conversion.

What I would like to know :

Has anyone successfully done this conversion?
If so , was there any major issues?
Anything else to note, other than what I already listed.
Thanks
Paul

 

[Don S]

Re: OMC Cobra to Volvo Penta DP-S Conversion

You may seriously want to reconsider. Yes it can be done, I have done it and you can see what the process was in the link below.
http://www.4shared.com/account/file/52230280/4fb01885/OMC_KC_to_Volvo_DP_Conversion.html

First, I have to assume you meant an 88 boat instead of a 98 since OMC didn't exist in 98.
Second. While the conversion did work there are several other factors now that makes it not such a good ideal.
Couplers. The coupler is no longer available from anywhere for the 460 Ford engine.
Exhaust manifolds. The manifolds are also no longer available from any source for the 460 Fords.
Both of these are needed to run a 460 Ford.

 

[HT32BSX115]

Re: OMC Cobra to Volvo Penta DP-S Conversion

There's actually someone that is now making those couplers I think. (Although one member that bought one had to send it back because it was defective)

There a set of manifolds on ebay right now ($500 each side).... Doug Russell has them, 1 set. (ONE)

Don't waste any money on the 460 OMC. So far I have sold most of the OMC stuff I had for a grand total of about $1500........... . (AND I still have the vertical drive left if anyone wants it!!)

If you really LOVE that boat and cannot part with it do what I did and find yourself a newer engine and drive combo. VP/Mercruiser, whatever, and swap it out.

Oh, and by the way, no adapter needed, For the most part, all the holes match up.....(drill 2 extra bolt holes for a Bravo)

(I like the 454/Bravo III)

Regards,



Rick

 

[paulcierra26]

Re: OMC Cobra to Volvo Penta DP-S Conversion

Thakyou for taking the time to reply to my/maybe/hopefully project
You are correct my Drive is 1988 Vintage.

I am a little scared now as I didin;t know anything about the Manifolds or Couplers.

I assume the Coupler from my Corbra leg or the Coupler from my new Volvo Penta DP-S leg won't work?

The exhaust maniflods on my Ford 460 won't work either? does this mean I need to find Volva Penta 460 Exhaust Manifolds and all the associated hardware somewhere?

Yes , I really like my ole Cierra but not enough if its gonna cost a ton of work and money$$ , i'm not so sure anymore.

I got a good deal on this DP-S Leg from a friend and my Cobra Leg has given me lots of grief so I was looking forward to doing this conversion.

I wonder why "Marine Parts Express " neglected to mention these major obstactles?

Paul

 

[Reel Poor]

Re: OMC Cobra to Volvo Penta DP-S Conversion

I am a little scared now as I didin;t know anything about the Manifolds or Couplers

I assume the Coupler from my Corbra leg or the Coupler from my new Volvo Penta DP-S leg won't work?.

Yes it will work but when it fails there are none available.

The exhaust manifolds on my Ford 460 won't work either? does this mean I need to find Volva Penta 460 Exhaust Manifolds and all the associated hardware somewhere?

Yes they will work for the conversion but like the coupler, when they fail there are none available, nowhere, nada, can't be found.

The reason for this is, nobody uses the 460 Ford engines in marine applications anymore.

 

[Don S]

Re: OMC Cobra to Volvo Penta DP-S Conversion

I assume the Coupler from my Corbra leg or the Coupler from my new Volvo Penta DP-S leg won't work?

The coupler bolts to the flywheel of the engine, has nothing to do with the outdrive itself. There isn't a Volvo coupler that fits on a Ford 460 engine, because Volvo never used a 460. Neither did Mercruiser.
OMC was the ONLY company that used the Ford 460, and that was only for 4 years, (87 thru 90). So there just wasn't any money in it for the aftermarket people to make couplers and exhaust manfolds for so few engines, and since OMC went out of buisness over 10 years ago, there are no more OEM parts made for it either.

 

[HT32BSX115]

Re: OMC Cobra to Volvo Penta DP-S Conversion

If you don't swap out the whole mess, you'll need to find another drive and just replace your current one.

It will be pretty hard to get anything for that boat with no drive on the back and a 460 under the hood......some of us learn the hard way.....welcome to the club


There usually 1 or 2 few of them on ebay I think. You need the 1.43:1 ratio King Cobra vertical drive that holds 108oz of drive oil. They only made it for the 460. If you lived up here in the NW, I would even help you install the one I have on your boat! (As long as you agreed to sell it somewhere else away from here!! )

Your best bet is to find a used bigblock VP or Merc Bravo I II III combo out of a damaged(NOT SUNK) boat and swap the whole mess.



Good luck...


Rick

 

[Don S]

Re: OMC Cobra to Volvo Penta DP-S Conversion

One other possibility. Since your 460 is still usable, go ahead and upgrade the drive to a Volvo. Now, while you are using your boat, you have time to locate a Chevy big block to replace it. OMC and Volvo both used the Chevy BB, so manifolds and couplers are easy to come by.

 

[HT32BSX115]

Re: OMC Cobra to Volvo Penta DP-S Conversion

That might be a good possibility since the inner transom plate for a 454/OMC bell housing mount appears to be the same.

It would certainly be better than swapping the whole mess...

He would need to find a 454 with an OMC Bell housing though. They sometimes show a part but when you call them they either say it's back ordered or unavailable. I just recently sold my flywheel housing off my 460. The buyer told me that it simply is not available from anywhere (except salvage) I found a "current price" of over $600 (then it said "no longer available" I was going to pile mine into the aluminum recycle I have!!

The following picture from Doug Russell Parts shows the (<1988 7.4L> part number for the flywheel housing.....The inner transom plate (if this parts list is correct), is the same as for a 460.


Since you have a (good condx?) DP-S drive then it will probably be worth it to start scrounging parts...

 

[Bondo]

Re: OMC Cobra to Volvo Penta DP-S Conversion

Ayuh,... If We're looking for Work-arounds to keep this barge afloatin',...

I Wonder if a Coupler for a Merc.470 is Close enough,..??..??
It ain't a Chevy bolt pattern,+ I doubt Merc came up with their Own, but maybe...
That'll leave the Ford option,..??
Comparisions of Other OMC couplers shows that overall Length might be the Issue with adaptation...
And,..
For the Manifolds,...
I've seen Adapter Plates, that'll allow bolting on BBC manifolds to the Fords...
You'll have to search around the Hot Rod boating forums for them,...Maybe V-drives,+ Jet forums too...

 

[Don S]

Re: OMC Cobra to Volvo Penta DP-S Conversion

The 470 couplers are shorter (not as much spline contact, along with a LOT smaller OD and weaker rubber. One could try, but I doubt they would put up with a BB engine even if the length was OK.

 

[Howard Sterndrive]

Re: OMC Cobra to Volvo Penta DP-S Conversion

there is a performance marine header system on the market for the 460:
http://www.cpperformance.com/detail.aspx?ID=282

big bux...all stainless....and no guarantee of long term availability.

Hardin was offering a 460 cast manifold I thought but no mention of it anymore....

 

[Don S]

Re: OMC Cobra to Volvo Penta DP-S Conversion

Best exhaust system aint worth a dime if you don't have a coupler.

 

[dan t.]

Re: OMC Cobra to Volvo Penta DP-S Conversion

check out Kodiac Marine jet drive systems, they used to use ford 460s,may still have parts available, I seem to remember they used aluminum manifolds so this might not be an option for salt water,good luck

 

[paulcierra26]

Re: OMC Cobra to Volvo Penta DP-S Conversion

Don, thankyou for the link to your document showing your conversion on the Bayliner 2858 going from OMC King Cobra to Volva Penta Stern Drive.

Everything you encountered looks EXACTLY like my 1988 26ft Bayliner Cierra, Leg, Motor , Engine Compartment, Shift Cables, etc.

The only thing I am still confused on is the "Coupler"
I read you write-up a couple of times and you didn't mention pulling the motor to change the Coupler.

I have the UJoint/Drive Shaft from my old King Cobra and the near new 2006 DP-S leg that I bought has the Ujoint/Drive Shaft attached to its leg as well.

Can I make something work without pulling the motor and changing the Coupler that attaches to the Bell Housing?

If I do need a Coupler , is this Coupler some special conversion piece that attaches to the OMC 460 Bell Housing and then has Volvo Penta Splines for accepting the new DP-S Drive Shaft coming from the DP-S leg?

Was the Coupler made by OMC during the transition time when OMC was being taken over by Volvo Penta ?

Thankyou Rick and everyone else for your help as well.

 

[HT32BSX115]

Re: OMC Cobra to Volvo Penta DP-S Conversion

That coupler is a pretty important piece.

It bolts onto the same studs that the flywheel bolts to. The Ford 460 crankshaft has a rather unique bolt pattern that is simply different from all the other crankshaft bolt patterns.

Mercury Bravos for example have the coupler bolting to the flywheel similar to a clutch pressure plate.

The engine on just about all stern drives MUST be removed to get to the coupler....

If your coupler is "ok" you should have no problems making the conversion work. The problem comes when (if) the coupler fails. When that happens it's a complete show stopper(unless you can find another 460 coupler). That's why you don't want to spend too much money on the current set up. Or spend too much money modifying it to work with the Volvo, unless you can find a complete 454/OMC w/flywheel housing to replace it with. ......you could run it with the 460 whilst looking for a complete 454/housing/manifolds/etc set-up etc.........

You might also consider a complete Mercruiser 454/Bravo-I II III setup and just sell the DP-S drive and all the OMC stuff......

lot'sa options there..........

 

[Don S]

Re: OMC Cobra to Volvo Penta DP-S Conversion

You might also consider a complete Mercruiser 454/Bravo-I II III setup and just sell the DP-S drive and all the OMC stuff......

If you had the DP-S drive on and working, there is no way in the world you would want to change it over to the Merc Bravo III, The DP-S is a much better and more effecient drive. Plus you already have it, all you need is a Chevy BB engine, not the whole thing.

If your coupler is "ok" you should have no problems making the conversion work. The problem comes when (if) the coupler fails. When that happens it's a complete show stopper(unless you can find another 460 coupler). That's why you don't want to spend too much money on the current set up. Or spend too much money modifying it to work with the Volvo, unless you can find a complete 454/OMC w/flywheel housing to replace it with. ......you could run it with the 460 whilst looking for a complete 454/housing/manifolds/etc set-up etc.........

That is exactly what I am trying to explain. The manifolds and coupler may be good now, but if the coupler went out on you in a year, you are done. A new one doesn't exist so you have no way of making your boat work again.

 

[dan t.]

Re: OMC Cobra to Volvo Penta DP-S Conversion

if all the splines are the same and the VP uses a coupler that bolts to the flywheel like a 280,w hat is stopping you from redrillingthe flywheel to fit an available coupler

 

[Don S]

Re: OMC Cobra to Volvo Penta DP-S Conversion

It's nothing like a 280. That is a flex plate, this is a rubber hubbed coupler that bolts to the crankshaft.

 

[dan t.]

Re: OMC Cobra to Volvo Penta DP-S Conversion

thanks Don ,I stand corrected, only vp drive I had anything to do with was a 280