OMC King Cobra to Mercruiser conversion

[sausrigging]

Is the King Cobra cutout bigger than the Bravo cutout? My understanding is mercruiser cutouts are the same? Does anyone have definitive info on the KC transom cut out size? I was thinking I could use the MerCruiser Transom Adaptor Kit if the alpha one gen 2 set up I have is too small?
Thanks in advance, my experience is with shaft driven boats, well actually wind driven boats

 

[Don S]

Re: OMC King Cobra to Mercruiser conversion

I know the dog clutch King Cobra is the same cutout, and I as I recall the cone clutch King Cobra is the same cutout but has 2 extra holes at the top of the cutout not found on the dog clutch style.

 

[sausrigging]

Re: OMC King Cobra to Mercruiser conversion

I know the dog clutch King Cobra is the same cutout, and I as I recall the cone clutch King Cobra is the same cutout but has 2 extra holes at the top of the cutout not found on the dog clutch style.

Awesome, "know" is a lot better than 'ive read somewhere'! I have the cone clutch on my 93 donzi 18 classic
, i just picked up a vortec 5.7 with a brand new jasper block and a alpha one gen 2 drive complete still bolted thru the transom cheap, cant wait to yank the 351 out.
Now, on to mounting, how different are the motor mounts and locations?
TIA

 

[Don S]

Re: OMC King Cobra to Mercruiser conversion

Well, there is going to be differences in the front mounts on the stringers, the Ford and Chevies are different. What you have to do is first get all the OMC stuff out of the boat, make sure the transom and stingers are all solid, then the Gimbal housing for the Merc has to have a new gasket installed and intalled on the transom. Then you will need to set the new engine in place with the rear mounts bolted down, and use the alignment bar to get the engine close to aligned. From there you measure and make templates of where you want the stringer mount pads to be.
Then pull the engine back out and make your mounts and cut off the old ones to clear things as needed.
That's the nutshell version.

When you get to the point of installing the Merc stuff, start a thread over in the Mercruiser forum.

 

[sausrigging]

Re: OMC King Cobra to Mercruiser conversion

Well, there is going to be differences in the front mounts on the stringers, the Ford and Chevies are different. What you have to do is first get all the OMC stuff out of the boat, make sure the transom and stingers are all solid, then the Gimbal housing for the Merc has to have a new gasket installed and intalled on the transom. Then you will need to set the new engine in place with the rear mounts bolted down, and use the alignment bar to get the engine close to aligned. From there you measure and make templates of where you want the stringer mount pads to be.
Then pull the engine back out and make your mounts and cut off the old ones to clear things as needed.
That's the nutshell version.

When you get to the point of installing the Merc stuff, start a thread over in the Mercruiser forum.

You are a generous man Don, thank you!

 

[sam60]

Re: OMC King Cobra to Mercruiser conversion

When you get to the point of installing the Merc stuff, start a thread over in the Mercruiser forum.

Also when you are at that point, please post a message in the OMC Forum directing us to the repower. I am interested in what you are doing.

 

[HT32BSX115]

Re: OMC King Cobra to Mercruiser conversion

Awesome, "know" is a lot better than 'ive read somewhere'! I have the cone clutch on my 93 donzi 18 classic
, i just picked up a vortec 5.7 with a brand new jasper block and a alpha one gen 2 drive complete still bolted thru the transom cheap, cant wait to yank the 351 out.
Now, on to mounting, how different are the motor mounts and locations?
TIA

Howdy,

I removed a 460 Dog-clutch Cobra from my 87 Four Winns and replaced it with a (97model year) Gen VI 454 Bravo. The cutout WAS indeed the "same"

The additional 2 holes I had to drill for the additional 2 upper studs were easy to drill. I didn't have a template, so I removed the upper 2 studs from the Bravo Gimbal mount to locate the drill points. (The Alpha Gen II and Bravo both have the same number of studs)

A template would be better to use though.

I filled the holes in the (engine) side mount pads using marine epoxy mixed with powdered fiberglass before I mounted the engine to locate the holes for the 454.

It was also pretty easy. By the way, don't just "give" your OMC stuff away if it's still serviceable. I sold all my OMG King Kobra stuff (Craigslist, EBAY, etc) for about $3500 (total) piece by piece over a 3 year period!

Just about the all the major dimensions are the same also (like the distance from the crankshaft centerline to the propshaft centerline)

 

[sausrigging]

Re: OMC King Cobra to Mercruiser conversion

Awesome, I will be pulling the omc out this week, pics to come!

 

[sausrigging]

Re: OMC King Cobra to Mercruiser conversion

I cannot for the life of me remove the omc drive, this boat has spent nearly all its life in saltwater.

 

[Nivekt]

Re: OMC King Cobra to Mercruiser conversion

I cannot for the life of me remove the omc drive, this boat has spent nearly all its life in saltwater.

Fire hose with PB Blaster? I'm sorry I dont have any useful ideas.:sorry: How about some pictures of where you are having issues?

 

[sausrigging]

Re: OMC King Cobra to Mercruiser conversion

ill get some this morning..

 

[Don S]

Re: OMC King Cobra to Mercruiser conversion

I cannot for the life of me remove the omc drive, this boat has spent nearly all its life in saltwater.

Not uncommon for saltwater boats that never get the drive pulled for maintenance. Corrosion builds up around the 6 studs holding the drive to the pivot housing. I wouldn't spend a lot of time worrying about it either. Take the trim hoses off the cylinders or cut them off, they are probably corroded into the cylinders as well. Then remove the 2 pivot bolts holding the pivot housing to the gimbal ring, cut the bellows, hose, and shift cable, and it's off.
Now you have something to take apart at a later date.

 

[sausrigging]

Re: OMC King Cobra to Mercruiser conversion

Not uncommon for saltwater boats that never get the drive pulled for maintenance. Corrosion builds up around the 6 studs holding the drive to the pivot housing. I wouldn't spend a lot of time worrying about it either. Take the trim hoses off the cylinders or cut them off, they are probably corroded into the cylinders as well. Then remove the 2 pivot bolts holding the pivot housing to the gimbal ring, cut the bellows, hose, and shift cable, and it's off.
Now you have something to take apart at a later date.

Hi Don,
I got the trim cylinders off, and the 6 studs cut, Ive got the shift cable cut, Am levering on the thing hard and it comes out like 1.5" inches but then sucks back in.
Where are the two pivot bolts? The thing is so crusty its hard to make out whats what!

 

[sausrigging]

Re: OMC King Cobra to Mercruiser conversion

http://i81.photobucket.com/albums/j222/qcyacht/20130410_154038_zps3357d71f.jpg
http://i81.photobucket.com/albums/j222/qcyacht/20130410_153046_zps7a7ab25c.jpg
pressure washed the pool of mud from the prop to my face..

 

[Don S]

Re: OMC King Cobra to Mercruiser conversion

Am levering on the thing hard and it comes out like 1.5" inches but then sucks back in.

Then you don't need the pivot bolts removed, your problem is the shaft is frozen inside the coupler. The coupler is rubber and you are just stretching the rubber, and that is what's pulling it back in. Removing the pivot bolts isn't going to cure the problem.
I've had to cut the shaft where it goes into the couple to get them out.

 

[sausrigging]

Re: OMC King Cobra to Mercruiser conversion

That explains it!
I am thinking of taking the torch to it. I can squeeze a sawzall blade thru the cut bellows buts its tight and at a poor angle..

 

[Don S]

Re: OMC King Cobra to Mercruiser conversion

Cut the shaft inside the boat, between the coupler and the transom shield.

 

[sausrigging]

Re: OMC King Cobra to Mercruiser conversion

I seriously cannot see the shaft inside the boat..

 

[HT32BSX115]

Re: OMC King Cobra to Mercruiser conversion

http://i81.photobucket.com/albums/j222/qcyacht/20130410_154038_zps3357d71f.jpg
http://i81.photobucket.com/albums/j222/qcyacht/20130410_153046_zps7a7ab25c.jpg
pressure washed the pool of mud from the prop to my face..

I hate when that happens!



That is clearly NOT a Dog-clutch Cobra! (I don't think anyone said it was....)

When you get it all out, check the transom, stringers and floor of the bilge very closely for rot and water intrusion.

 

[Bondo]

Re: OMC King Cobra to Mercruiser conversion

I seriously cannot see the shaft inside the boat..

Ayuh,... Put the trim rams back on,...
With the drive Down, 'n usin' wood blockin',...
Block the top of the drive to the top of the transom housin'...

Then hit the trim switch, 'n see if the rams will slide it out, as far as you've been pryin' it out...
Leave it loaded up with the pressure...

If it Does,....
Spray a can of good penertratin' oil, All over inside the transom, Hopefully, ya might actually get some into/ at the coupler...

Ya might also try Wackin' the drive forward, while the rams are holdin' it out,...
a block of softwood, 'n a BFHammer would be the tools of choice...

Can ya pull some of the hull/ boat outa the way to get at the shaft, at the back of the motor,..??