Installing OMC460 King Cobra

[White Rhino]

Hello, boaters. I was given a 1987 Chris Craft Scorpion 230 that had been powered by an OMC 5.7 Cobra, but the motor was missing. I bought, very cheaply, a 1987 Four Winns Liberator with an OMC 460 King Cobra. I want to put the 460KC in the Chris and have some questions. I've been told it will bolt on fairly easily because they are from the same year. Anyone have experience with this swap? Can I reuse the y-pipe from the 5.7 to convert the 460KC to prop exhaust without ruining the outdrive or having performance suffer? I've read the Stuart Hastings site and it has given me confidence that I'm not trying an impossible task by getting involved in OMC, especially since this boat was OMC, and Merc is too expensive for me right now. Someday, I may hunt down that Merc setup and do that, but right now my goal is to be on the water in the spring for cheap. So far, my total investment is under a grand. In lurking around these forums I've seen plenty of good technical advice, and plenty of anecdotal stuff and I welcome both. I'm as newbie as they get, so it's all for the good. So, come on guys, bring it on.

Kind Regards,

Bill

 

[Don S]

Re: Installing OMC460 King Cobra

Before you get it in there understand one thing there are some very important parts needed for a marine engine that are not available for the 460's anymore. The engine coupler, and the exhaust manifolds and risers.

 

[White Rhino]

Re: Installing OMC460 King Cobra

Thanks, Don. Those two items are what I keep hearing about. The previous owner of the Lib assures me the manifolds are good. My intent is to get two or three seasons out of this setup, then repower with a rebuilt Merc Big Block and Bravo outdrive, the apparent preferred option for performance, fuel efficiency and parts availability. But can I use the y-pipes and go with prop exhaust? Does it fit properly? Does the whole thing fit as well as I've been led to believe?

 

[Don S]

Re: Installing OMC460 King Cobra

Never tried that swap, so can't tell you what you will find. The Y pipe is the same as a Chevy SB, so that won't be a problem. The electrical plug is the same, and cables work the same for throttle and shifter. Location of the motor mounts on the stringers may be different. I think the 460 is farther back than the Chevy. The gear ratio in the drive is a little different, but the 460's always ran a KING Cobra drive which was heavier built than a standard Cobra drive. I also don't know if the inner transom plate is the same for Ford and Chevy. Might want to check that out before you try to install the engine.

 

[HT32BSX115]

Re: Installing OMC460 King Cobra

Sheesh! They must have made more than 2 460 King Cobra Liberators!!!....What were they thinking!!!

Well, I just LOVE anecdotal advice. It never did me much good though.

There's no reason you couldn't put the 460 King in the other boat. You best bet might be to swap everything from the FourWinns Lib over though. I am pretty sure that the bell housing and transom plate for the 5.7 are different enough to not be able to use it with the 460. You may be able to use the gimbal and drive.

For 1987 the drive ratio for the 5.7 was 1.41:1 and the drive held about 64oz of drive oil. The 7.5L was 1.43:1 and held 108oz of oil (almost DOUBLE). This could mean that the drive may be different enough to not fit the other gimbal(I have heard that they do fit.though...the main difference is in the lower case.

The drive for the 7.5 is also a LOT heavier (Like Don said) I know, I still have mine sitting on the garage floor.

I'm guessing that your Liberator is probably has Thru-hull exhaust. So you won't have a Y-pipe. The Y-pipe tubes, 3.5" dia, should measure 28" center-to-center and 17" from the bottom of the opening to the top of the tubes.

You won't affect the performance much. I had Corsa Captains Call electric diverters on my Liberator and all it did when open was make a lot of noise. It didn't seem to go any faster.....They're sitting in a box on the floor too!

I could have a look at my transom plate but you have 2 there and you can compare them. Now for the anecdotal advice......That 460 will be fine in a truck! I wouldn't let one get anywhere near a boat!!! (just kidding. Mine ran this boat for 17 years before the cam went flat!)


Good luck....


Rick

With a Liberator powered by

 

[White Rhino]

Re: Installing OMC460 King Cobra

Thanks, Don. I'll check into that inner transom plate. This is just the type of information I was hoping to obtain. These forums may make a wrencher out of me yet.
Rick, What can I say. One post, both requests filled. And while I've got to take your personal experience as sound, and the fact that you swapped out your 460KC for a Merc drivetrain as a reasonably strong suggestion against my project, I'm just thick enough to go ahead and try anyway. The fit info is great, just what I wanted. Now what are the chances you have that oh, so hard to find manifold on your garage floor? Not that I need one now, but.... Anyway, some grunt work over the winter, and I'm in the water come spring. A couple years down the road, I hope to repower with what you're running in your Lib now.
My plan was to use everything from the Lib, and I'll pay specific attention to the transom plates, inner and outer, the bell housing, and I'll measure the y-pipes already in the Chris to see if they match your given specs. All great places to start. I'm sure I'll be back in here along the way trying to get some help to keep me from pulling my hair out. That will be time to cue the "I told you so"'s, but I know what I brought on myself, so it will be fine. Thanks again for the time and information. Any more would also be appreciated.

Hope to be in your wake soon,

Bill

 

[HT32BSX115]

Re: Installing OMC460 King Cobra

Hmmmm...


Well you'll notice I did not say "don't do it"

I don't see any reason why you cannot. (other than all the reasons Don mentioned ----can't buy manifolds/coupler AND if it's got a newer electronic ignition, ignition--coils, computer, etc)

Actually I looked at Doug Russell's site recently and saw that they have prices for manifolds now.....about $1400 EACH!!! (not including shipping!!!)

I also saw a coupler on ebay from Doug Russell for a starting price of $600+

This all indicates what always happens when parts for existing "stuff" becomes very scarce...The people with the parts use the supply/demand concept to their advantage..... I don't know if I would want it any other way I guess. It behooves us all to do our homework very carefully!


The good thing probably is that when you do finally pull all that junk out of your boat to put in something a little more modern (and available), as long as your manifolds are usable they're probably worth as much as new ones for other engines on ebay etc.

Your coupler will also be in GREAT demand. I sold mine on ebay for about $225.

I haven't even tried to sell the other stuff......I should get on that....

If you want any of the "stuff" I have, drop me a PM.......This is not the place to discuss for-sale stuff....(& yes I still have that Y-pipe......but I'm thinking yours will work.....)


Regards,


Rick

 

[JCF350]

Re: Installing OMC460 King Cobra

Actually I looked at Doug Russell's site recently and saw that they have prices for manifolds now.....about $1400 EACH!!! (not including shipping!!!)

Small price to pay to have a big block!

 

[HT32BSX115]

Re: Installing OMC460 King Cobra

Small compared to what?

Complete (2) manifold/riser/elbow kits for a 454/502 Mercruiser range from $500-700 incl gaskets etc!

I only paid $5k for my 97 Merc 454 + Bravo III + gimbal, +harness and hardware. (122 hrs since new)

The only thing I could have done better.....would have been to NOT buy the boat with the King Kobra in it!!

Small price to pay to have a big block!

 

[JCF350]

Re: Installing OMC460 King Cobra

Small compared to what?

Complete (2) manifold/riser/elbow kits for a 454/502 Mercruiser range from $500-700 incl gaskets etc!

I only paid $5k for my 97 Merc 454 + Bravo III + gimbal, +harness and hardware. (122 hrs since new)

The only thing I could have done better.....would have been to NOT buy the boat with the King Kobra in it!!

Ya can't make a MOUNTAIN MOTOR out of a 454. That toothpick they have for a crankshaft just won't take the pressure.

Ref: NHRA limiting Pro stock to 500 cu. in. some years back because those "overbored overstroked small blocks with a toothpick for a crankshaft and to dam many head bolts for an engine" couldn't compete with the 700 to 800 cu.in. Fords and Chryslers and stay together. I call it "The day NHRA banned big blocks in Prostock"

 

[Bondo]

Re: Installing OMC460 King Cobra

The only thing I could have done better.....would have been to NOT buy the boat with the King Kobra in it!!

Ayuh,.................................

I'm sure I'll be back in here along the way trying to get some help to keep me from pulling my hair out. That will be time to cue the "I told you so"'s,

That's Ok Bill,................ I'll be here Waitin'........................................

 

[HT32BSX115]

Re: Installing OMC460 King Cobra

Um.....NHRA is a Mercruiser, Volvo, and OMC issue?

That's all great for dragsters etc. BUT if you tried to put that sort of HP/torque through a OMC 460 King Cobra coupler, there'd be a lot of burning rubber smell and a lot rubber powder in the bilge! Then you'd looking for a "tow"!!!

I venture to guess that the King Cobra drive, as strong as it was touted to be wouldn't survive long either. One good "straight-arm" hole shot, if it didn't spin the coupler it would probably eventually break the drive.

so......as it were this is a moot point!
("mute" for those of you in Rio Linda!)

Cheers,

Rick

Ya can't make a MOUNTAIN MOTOR out of a 454. That toothpick they have for a crankshaft just won't take the pressure.

Ref: NHRA limiting Pro stock to 500 cu. in. some years back because those "overbored overstroked small blocks with a toothpick for a crankshaft and to dam many head bolts for an engine" couldn't compete with the 700 to 800 cu.in. Fords and Chryslers and stay together. I call it "The day NHRA banned big blocks in Prostock"

 

[JCF350]

Re: Installing OMC460 King Cobra

Um.....NHRA is a Mercruiser, Volvo, and OMC issue?

That's all great for dragsters etc. BUT if you tried to put that sort of HP/torque through a OMC 460 King Cobra coupler, there'd be a lot of burning rubber smell and a lot rubber powder in the bilge! Then you'd looking for a "tow"!!!

I venture to guess that the King Cobra drive, as strong as it was touted to be wouldn't survive long either. One good "straight-arm" hole shot, if it didn't spin the coupler it would probably eventually break the drive.

so......as it were this is a moot point!
("mute" for those of you in Rio Linda!)

Cheers,

Rick

With the thread drifting, the 454/502 merc comment came up so I pulled it aside even more. I would not use anything with a rubber coupler to begin with.

 

[Don S]

Re: Installing OMC460 King Cobra

I would not use anything with a rubber coupler to begin with.

Sure does cut down your options with an IO now, doesn't it.

 

[HT32BSX115]

Re: Installing OMC460 King Cobra

Yeah I guess you're right! Once the thread begins to drift a little.....anything goes!

If we run it long enough it turns into an oil thread anyway!!

Yup. You're right. A 460 is a fine engine......For Dragsters, motorhomes, trucks, V-drives and Jetboats!

Mercury Racing usually doesn't mess with them! but......isn't the 460 gone from the Ford line-up? so it's sort of like the Y-block.....out dated and gone. I like old vintage stuff......I have a Y-block in my 1955 Ford F-600....

What's this got to do with OMC/VP/Merc I/O's ?

Nothing.

With the thread drifting, the 454/502 merc comment came up so I pulled it aside even more. I would not use anything with a rubber coupler to begin with.

 

[HT32BSX115]

Re: Installing OMC460 King Cobra

Oh....and by the way......here's a "Mountain Motor" and I think it may even have a rubber coupler......

Click on specifications.....Isn't 1200 marine HP a lot for a toothpick?

http://www.mercuryracing.com/products/sterndrives/hp1200sci.php

Ya can't make a MOUNTAIN MOTOR out of a 454.
That toothpick they have for a crankshaft just won't take the pressure.

 

[JCF350]

Re: Installing OMC460 King Cobra

Sure does cut down your options with an IO now, doesn't it.

Only the newer ones. I'm building a 806 inch motor and plan to use one of the 3 Dana's I have laying around or maybe a II drive.

 

[JCF350]

Re: Installing OMC460 King Cobra

Oh....and by the way......here's a "Mountain Motor" and I think it may even have a rubber coupler......

Click on specifications.....Isn't 1200 marine HP a lot for a toothpick?

http://www.mercuryracing.com/products/sterndrives/hp1200sci.php

Yes it is (1200hp), how long do you think it will last?

Still only a 557cu in motor (never heard of anything less than 700cu in called a mountain motor before). And needs blowers to get 1200. Ford did 800hp out of a 2 liter some years back with twin turbos so high horse power is easy to get using forced induction. One thing you get with large cubic inch engines is the ability to develop large amounts of torque in the lower rpm ranges (still normally aspirated) while maintaining reliability to push a "boat" not that a flimsy little piece of plastic shown in the Merc ad (whack a dock or try to fish with that thing).I would highly doubt a rubber coupler, I would doubt even aluminum splines in the coupling mechanism but then dumber things have been done.

My reference to NHRA was just that, a reference, in comparing the relative strength of the engines.

Ford discontinued the 460 in favor of the diesel. GM still has the 454/502 because they can sell them cheap and the major market for them is for trucks of the type that Ryder and Penske buy, who are going to write them off in 3 to 5 years. Why pay for long term longevity when your not going to keep it for the long haul?

So what kind of oil do you prefer?

 

[HT32BSX115]

Re: Installing OMC460 King Cobra

I probably have you beat.......I've never heard of a "Mountain Motor"


I'm not going to reveal what kind of oil I use!!!


Actually the 460 was a pretty good engine for an I/O. It's a shame that no one supports using it any more...I don't really know why OMC switched to the 454. The 460 outlived OMC by a wide margin I think.

Still only a 557cu in motor (never heard of anything less than 700cu in called a mountain motor before). And needs blowers to get 1200.

 

[whywhyzed]

Re: Installing OMC460 King Cobra

I would not use anything with a rubber coupler to begin with.

OMC stringer the only i/o I can think of that uses solid spline coupler.
Oh wait - is the TR/TRS solid on the trans output? maybe