View Full Version : OMC Cobra - Burnt up Gears - What are my Options?

05-17-2015, 01:51 PM
Looks like I burnt up the gears in my 4.3l OMC Cobra - turns out the drive oil leaked. Made a knocking noise and then lost power to the drive. I took the top off and can see the gears are chewed. My questions are:

1. Does the oil circulate between upper and lower unit? Is there a chance the lower unit is damaged too?

2. If it's just the upper unit- how hard is it to rebuild? Looks like I can get a parts kit off ebay for about $400

3. What's the best (cheapest) option? Would it be totally unsafe to buy a used outdrive?

Thanks guys

05-18-2015, 05:37 PM
If the upper is damaged you can count on having debris in the lower. You might want to look into swapping to a alpha gen 2. The value of your boat will go up in what the swap costs.

05-18-2015, 09:37 PM
Besides the drive, what else would need to be swapped? Is it difficult? Approximate cost? Oh...and most importantly- would I gain/lose any speed?:shades::yes:

05-19-2015, 05:37 AM
You would need a new transom assy , shift cables and shift bracket. I would guess around 1500 to 2000 buying used and doing the work yourself. If you plan on keeping the boat it is worth a thought. It is the parts availability of the alpha. A bravo conversion would be much more expensive. It all depends on your long term plans for the boat and of course that damn budget !!

05-19-2015, 06:32 AM
The Volvo sx may be an option it is a direct replacement for the cobra should hang on what is there

Bobby D
05-20-2015, 12:14 PM
Yep X2 what Matt said, although not many (other than me) are installed on Donzi boats the SX outdrive is very robust and can handle a lot of HP.

05-20-2015, 12:23 PM
Yep X2 what Matt said, although not many (other than me) are installed on Donzi boats the SX outdrive is very robust and can handle a lot of HP.

Did you do the swap yourself? If so, was it as simple as taking the old outdrive off and sliding the new one in? Any differences with handling/performance?

Definitely looks like a viable option. An alpha would be nice, but I'd like to keep things simple for now

05-20-2015, 09:50 PM
not sure where you are located but if you search ebay and craigslist you may find a replacement drive there are a few SX drives on CL in the NYC metro area

Bobby D
05-22-2015, 12:18 PM
Sorry for not being clear my set up is all Volvo and not a swap from a Cobra to VP SX drive. The SX replaced the original Volvo 250 outdrive and all the work including transom modifications were done by the previous owner. It was a complete change over including a VP 5.7 GSi that was rated at about 310HP at the prop, that motor died several years ago and has been replaced with a SBC 406. He purchased the 1.43:1 SX outdrive and transom shield first with a plan to install a BB Chevy, later he decided to go with the SB instead.
Not sure what year yours is but I believe the Volvo SX drive is basically the same drive as the OMC Cobra SX which they started using when OMC and Volvo did their joint venture starting in 1994. As long as you use the same gear ration it should work, below is some information I found on the web that may help you. Also if you research the issue Iím sure you will find that someone has already figure it out.

The new modern OMC factory and the Cobra engineering attracted the attention of Volvo and in 1993 OMC and Volvo entered into a joint venture and began producing a hybrid sterndrive with the OMC Cobra transom plate assembly and the excellent Volvo cone clutch outdrive. Sold as the Cobra by OMC and the SX Drive by Volvo, this drive had the best of both manufacturers. Because the new hybrid sterndrive used the same transom plate as the Cobra, Volvo now had a drive that would bolt into the same size transom cutout hole as the Mercruiser.
The new Cobra/Volvo hybrid sterndrive shared only the transom assembly with the 1986-1992 OMC Cobra. Everything behind the transom plate bell housing was Volvo engineering. Realistically, with the introduction of this sterndrive in 1993, we can say that the OMC sterndrive engineers were put out of business when the last of the OMC designed sterndrives finished production in 1992. On December 23rd 1998, Volvo purchased the Lexington, Tennessee factory and all of the production rights to the OMC sterndrives, thus officially ending the OMC sterndrive business

Bobby D
05-22-2015, 02:39 PM
Pictures of the transom shield before and after the motor installation and a short video of the first start.