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TOPIC: Cobra Dog to Cobra SX Cone

Cobra Dog to Cobra SX Cone 25 May 2016 04:44 #1

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Before and After:

Total cost included everything from drive components, F6B-9 water pump, etc. etc. ......... all the way to the last bolt, cotter pin, paint and a New Michigan Match prop. = $2052.00

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" WET EVER "
1989 2459 TROPHY OFFSHORE 5.8L COBRA / SX
mmsi 338108404
mmsi 338124956
"I started with nothing and still have most of it left"

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Last Edit: by dktool.

Cobra Dog to Cobra SX Cone 25 May 2016 13:04 #2

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Impressions?

eBayd components, I am assuming? (not new)

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Cobra Dog to Cobra SX Cone 25 May 2016 15:42 #3

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Download_Complete wrote: Impressions?

eBayd components, I am assuming? (not new)


No difference in performance, handling or backing / docking. Only easier and quieter shifts.

Locally sourced complete drive from a guy that went BOOM at the launch ramp from a "REPAIRED" fuel tank.
He survived, but the boat flat lined.

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" WET EVER "
1989 2459 TROPHY OFFSHORE 5.8L COBRA / SX
mmsi 338108404
mmsi 338124956
"I started with nothing and still have most of it left"

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Cobra Dog to Cobra SX Cone 25 May 2016 16:15 #4

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Very nice. :)

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Cobra Dog to Cobra SX Cone 25 May 2016 16:26 #5

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Does that just replace the OMC outdrive using the same transom assembly?

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88 Capri 2150 305 OMC
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Cobra Dog to Cobra SX Cone 25 May 2016 17:50 #6

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montagc wrote: Does that just replace the OMC outdrive using the same transom assembly?


Seems to be.

I can make out OMC on the transom assembly in his pic.

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Cobra Dog to Cobra SX Cone 25 May 2016 17:52 #7

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Download_Complete wrote:

montagc wrote: Does that just replace the OMC outdrive using the same transom assembly?


Seems to be.

I can make out OMC on the transom assembly in his pic.


Huh. Interesting. Good to know that there are options besides the SEI unit should my Cobra spew gear chunks.

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88 Capri 2150 305 OMC
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Cobra Dog to Cobra SX Cone 25 May 2016 18:11 #8

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montagc wrote: Does that just replace the OMC outdrive using the same transom assembly?


The ONLY, and I repeat, ONLY component that does NOT have to be changed is the transom shield.

The above statement is for a PROPER / CORRECT swap.

The web has many accounts of the conversion being done and as with a lot of things on the net, there is a lot of mis, to bad information out there.
Some accounts state the you just have to swap the leg.............WRONG
Others say the SX gimble housing needs to be used.................CORRECT, BUT they fail to mention the SX inlet water hose also needs to be used.
The gimble from the original can be used BUT, the side thrust surfaces do not extend to the rear far enough to do any good.
Regarding trim cylinders, they too need to come from a SX unless someone wants to screw around making bushings or different mount shafts.
The SX shafts are larger diameter and therefore the bores in the cylinder housing and rod ends are larger.
Also, the prop shaft is 19 spline instead of 15 spline so a new prop or a re-hub is needed.

To anyone saying there is a "kit" available to do the swap, I call a very large B.S.
If there is such a kit, it wouldn't be worth its weight in scrap metal.

I do have the transom shield from the SX but did not need to swap it. NOTE: the only difference in the 2 shields is the shift cable outlet location. It is about 2" lower on the SX shield but the Cobra cable exit point lines up fine and presents no issue when tilted through the full range and turned lock to lock.

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" WET EVER "
1989 2459 TROPHY OFFSHORE 5.8L COBRA / SX
mmsi 338108404
mmsi 338124956
"I started with nothing and still have most of it left"

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Last Edit: by dktool.

Cobra Dog to Cobra SX Cone 25 May 2016 19:11 #9

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montagc wrote:

Download_Complete wrote:

montagc wrote: Does that just replace the OMC outdrive using the same transom assembly?


Seems to be.

I can make out OMC on the transom assembly in his pic.


Huh. Interesting. Good to know that there are options besides the SEI unit should my Cobra spew gear chunks.



While a great alternative, these drives were made in small numbers and are not readily available. I looked for one for some time when I had mt 2858 and never found one in good condition at a reasonable price.

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Cobra Dog to Cobra SX Cone 25 May 2016 19:46 #10

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Norton Rider wrote:

While a great alternative, these drives were made in small numbers and are not readily available. I looked for one for some time when I had mt 2858 and never found one in good condition at a reasonable price.


All Volvo Penta SX-M models are exactly the same as the SX Cobra and where produced for YEARS by the thousands.
There is no shortage of them, the boats they're attached to just haven't died yet so you don't see many in the used market.

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" WET EVER "
1989 2459 TROPHY OFFSHORE 5.8L COBRA / SX
mmsi 338108404
mmsi 338124956
"I started with nothing and still have most of it left"

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It's only a rock, get over it.

Cobra Dog to Cobra SX Cone 26 May 2016 00:25 #11

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dktool wrote:

Norton Rider wrote:

While a great alternative, these drives were made in small numbers and are not readily available. I looked for one for some time when I had mt 2858 and never found one in good condition at a reasonable price.


All Volvo Penta SX-M models are exactly the same as the SX Cobra and where produced for YEARS by the thousands.
There is no shortage of them, the boats they're attached to just haven't died yet so you don't see many in the used market.



Agreed... I was referring to the Cobra and not the Volvo.

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Cobra Dog to Cobra SX Cone 26 May 2016 11:25 #12

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The swap looks great and that is an upgrade I'd love to do on my boat if the right deal came along. I have a few marine mechanics I'm friendly with around here that I can get to keep an eye out for me for something like that.
As far as a kit being available, well I used to have documentation from Volvo Penta that showed that they did sell a kit, to upgrade the Cobra to the Volvo SX. What it consisted of was the Volvo pivot housing (this is the part of the transom assembly that tilts up and down that the drive mounts on to), an engine mounted water pump. As noted though you have to make up spacers for the trim cylinders and should use SX trim cylinders vs the Cobra ones.

www.marinepartsexpress.com/PDF/volvo/SX_Cobra.pdf

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Cobra Dog to Cobra SX Cone 26 May 2016 17:49 #13

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88fourwinns wrote: The swap looks great and that is an upgrade I'd love to do on my boat if the right deal came along. I have a few marine mechanics I'm friendly with around here that I can get to keep an eye out for me for something like that.
As far as a kit being available, well I used to have documentation from Volvo Penta that showed that they did sell a kit, to upgrade the Cobra to the Volvo SX. What it consisted of was the Volvo pivot housing (this is the part of the transom assembly that tilts up and down that the drive mounts on to), an engine mounted water pump. As noted though you have to make up spacers for the trim cylinders and should use SX trim cylinders vs the Cobra ones.

www.marinepartsexpress.com/PDF/volvo/SX_Cobra.pdf


If that is their rendition of a swap kit, it not worth it's weight in scrap PAPER.

They mention spacers, that is only to address limiting the trim cylinder stroke in the extended position.
They make no mention of the fact that you CANNOT directly install old style cylinders onto a SX lower without addressing the mounting rod diameter difference.
Then there is the issue of the thrust surfaces on the old style gimble. The picture on their literature makes it look like it's a non issue, maybe for their sales department it isn't but on MY boat it's a HUGE issue.

As with everyone's projects, how they go about it is their business unless it creates a safety / liability concern. (no further comment) :whistle:

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" WET EVER "
1989 2459 TROPHY OFFSHORE 5.8L COBRA / SX
mmsi 338108404
mmsi 338124956
"I started with nothing and still have most of it left"

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It's only a rock, get over it.
Last Edit: by dktool.

Cobra Dog to Cobra SX Cone 26 May 2016 19:01 #14

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I looked through that brochure, pretty sure I have a 15x17 on my cobra as it sits...

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Cobra Dog to Cobra SX Cone 26 May 2016 20:40 #15

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montagc wrote: I looked through that brochure, pretty sure I have a 15x17 on my cobra as it sits...


I was previously and am still running a 15 1/2" diameter.

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" WET EVER "
1989 2459 TROPHY OFFSHORE 5.8L COBRA / SX
mmsi 338108404
mmsi 338124956
"I started with nothing and still have most of it left"

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It's only a rock, get over it.
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Cobra Dog to Cobra SX Cone 26 May 2016 20:46 #16

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I never actually saw the instructions that they provided when they were selling these kits which was a long time ago. I to recall Don S on this site mentioning the issue with trim ram rod bushings, I have his write up on my computer and can look back to see how he solved it. He replaced an OMC 460 dog cluch King Cobra with an SX/DP, he of course changed the part that the drive mounts to (the pivot housing as its called in the OMC catalogs) but I don't think he replaced the part that the pivot bolts to, that swivels side to side with the thrust surfaces.
I have not compared them side to side to see how much further back that thrust surface extends on the VP transom shield vs the Cobra but based on what you're saying it must be substantial.

Anyway thanks for a first hand write up of how to do this, it will be helpful to anyone who is contemplating this conversion.

About the props, they were for sure wrong in their brochure, I have a 15x17 on my Cobra now and have tried a 15.5x15 just to see if it fit and it does.

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Last Edit: by 88fourwinns.

Cobra Dog to Cobra SX Cone 04 Jun 2016 18:34 #17

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One more bit of SX info, when I was doing my homework prior to the swap I was questioning the rust stains in the area circled in this photo.

It is an additional source of exhaust relief on both sides above the anti-cavitation plate.

(This a pic of the unit I purchased from the sellers ad.)

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" WET EVER "
1989 2459 TROPHY OFFSHORE 5.8L COBRA / SX
mmsi 338108404
mmsi 338124956
"I started with nothing and still have most of it left"

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It's only a rock, get over it.
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