OMC Cobra / Volvo Penta SX Mystery

[bkhitchens]

I have a 1994 Four Winns 278 with dual OMC / VP SX drives. I am contemplating replacing one of the drives, but cannot find the information I need to proceed.

Neither of the drives have the ID tag on the Port side of the drive. The engines are Ford 302, normally aspirated. The drive I am thinking of replacing is the Port side which I believe is a counter-rotational drive (Counter clockwise). In the engine compartment is a tag on the housing connected to the stern with the OMC Cobra logo. It lists the product number as 3868030. I cannot make out ratio, if there is supposed to be one listed here. I cannot make out anything under the type, either. I believe I may see a 6 in the ratio section but that may be scratches or dirt. I believe that the drive is an SX-M.

Am I correct that the drive is an SX-M? What interchanges between SX drives? Will it be hard to find the counter-rotational drive? Can I find the ratio of the drive with the information I have? If not, is there a way to manually determine it.

I am having some issues with the drive (another thread). The housings on the drive are really bad. I am hoping to find a rebuilt or good condition upper drive and throw my old lower on it for now. If this doesn't work, how hard will it be to buy a new housing and swap the innerds?

 

[Don S]

Re: OMC Cobra / Volvo Penta SX Mystery

There isn't a counter rotating SX drive, you just change the linkage.
The M model didn't start until 97 as I recall. You probably have an SX-S or SX-C model, a number of changes from the SX-M model.

Changing parts of the drive from one model to another may cause a problem, but replacing the whole drive is not a problem (assuming you have the right gear ratio).

 

[bkhitchens]

Re: OMC Cobra / Volvo Penta SX Mystery

Okay, thanks for the reply, Don.

I still have a number of questions. How do I tell exactly what model I have without the ID tag? Can I determine the ratio, Manually? I am contemplating engaging the gear and manually turning the engine one revolution and counting the amount of turns of the propeller. Would this give me an accurate final drive ratio? I also get the idea that the ratio is determined by the lower unit, not the upper. I see a lot of 21:26 geared uppers that seem to be proper for a variety of gear ratios. Is this correct?

It sounds like I could put a 21:26 geared VP/OMC SX drive for a 94 newer model on with the old lower and have the proper setup. Sound right?

Surely, there is someone out there that can answer my questions, and I would sure appreciate it. Thanks, Barry

It does make sense that the counter rotating drive is handled by the propeller and linkage.