Jim Barron, Editor, Tech Letters Trailer Boat Magazine 20700 Belshaw Avenue Carson, CA 90746-3510 Cc: Dan Gust and Tom Ski, OMC Technical Support Mr. Barron: I read the letter from Paul Elder ("Sorry," March 1998) with interest, out of sympathy for Mr. Elder, and because he shares a common misperception of the OMC Cobra "gearset problem." I've learned something about this since I bought a boat last summer with a similar Cobra drive. Trailer Boats Magazine can do a significant public service by recounting the correct story; the truth is less embarrassing for OMC, and some Cobra owners may avoid a similar failure. Early OMC Cobra drives occasionally destroyed their gearsets, with symptoms just like Mr. Elder's. In 1988, OMC decided the teeth on the sliding clutch dog were not inclined steeply enough. Early Cobra gearsets had teeth cut at 2°; subsequent Cobra gearsets have been cut at 5°. Presumably the sharper "bite" would help the clutch dog stay engaged. When Mr. Elder's OMC dealer says "old gears," the dealer is probably referring to an early-production 2° clutch dog. Anyway, the problem persisted, and in 1989 OMC decided the problem was really in the "transom shift cable." This is the lower cable visible to the starboard of the carburetor; it snakes through the transom, and connects with the gearchange mechanism in the vertical drive. OMC redesigned this cable, sent letters to all registered Cobra owners, and OMC dealers replaced them for free. If a cable failure destroyed a gearset, as apparently happened to Mr. Elder, OMC would also replace the gearset without charge. OMC says their cable-replacement letter went out in November of 1989. This was the letter that Mr. Elder's predecessor didn't get. OMC ended this extended warranty in 1994. OMC now says those early-production 2° gearsets were really OK. Contrary to what Mr. Elder was told, as well as OMC's original diagnosis, OMC now claims there were never any "bad gears." OMC says the real problem was the transom shift cable. I believe OMC is correct this time. Current Cobra owners can find out if their cable or gearset was replaced under warranty; call OMC at 847/689-6200, and ask for Technical Support. Please write down your questions before you call, along with the serial numbers from your engine, transom bracket, and vertical drive. OMC Technical Support is pretty good, and free; please don't waste their time. The current OMC transom shift cable has a red plastic cover; if yours doesn't, get it checked immediately. OMC recommends the Cobra transom shift cable be adjusted every fifty hours, with the usual annual maintenance. Replacement is a chore; the vertical drive must be removed for access. Cobra owners capable of re-greasing their own U-joints can change their own cables, but they'll need the OMC shop manual, OMC's streamlined adjustment procedure ("kw-shift.wps", dated 10/17/96), and possibly service bulletin #4052. Remove the exhaust bellows for access; a set of flare wrenches are handy, or you can cut the old cable and use a box-end wrench to remove it. OMC does not have a recommended replacement interval for the cable; four or five years seems prudent to me. OMC technical support claims you need a $50 special tool to adjust the cable; I bought the tool, and found it nearly useless; I suppose it would save some time for a professional tech. The OMC shop manual clearly explains how to adjust the cable without any special tools. Please disregard the section concerning "Core Wire Replacement"; OMC has repudiated this practice. A genuine OMC cable cost me $83, and it took few hours to install. I recommend replacing the "cable jacket" (a length of generic automotive plastic wire-loom flex pipe) at the same time. Non-do-it-yourselfers can expect to pay about $300 to replace this cable. While it is regrettable that Cobra drives had faulty cables, I believe OMC has acted honorably, and their redesigned cable has truly fixed the problem. I know OMC tried to contact Cobra owners about this problem because I have the form letter OMC sent to the original owner of my boat (copy enclosed). OMC can't really be faulted for ending their extended warranty; if they could be held liable for such failures forever, marine drives would be very expensive, like aircraft are today. This cable problem is insidious because the only likely symptom before gearset failure is stiff shifting. As the cable progressively binds up, shifting effort will gradually increase, and most owners won't notice because they only drive their own boats. Dave Brown of Brown's Marina (Canada) suggested that a properly-adjusted Cobra will "shift with a finger." If any reader's Cobra drive requires more than one finger to shift, I urge them to have their shift mechanism checked promptly. I learned this cable story by pursuing the original "bad gears" story that I heard about my own sterndrive. I purchased my boat last summer, and my gearshift was very stiff, but neither I nor the seller realized anything was wrong. So far, I've cleaned and re-greased my gearshift, replaced both shift cables (too long), replaced my transom shift cable (damaged and near failure), and I've replaced the centering spring in my electronic shift assist linkage (OMC had a defective batch of these). My Cobra will now "shift with a finger," at least in my driveway. I can offer only sympathy for Mr. Elder; he cannot be faulted for his ignorance of this "shifting timebomb" in his sterndrive. Indeed, if OMC is correct, neither the original owner nor the local OMC dealer understood the real problem, and Mr. Elder is paying for their collective ignorance. OMC dealers are "supposed to know" about this cable, and educate their customers. If all Cobra owners knew that an $83 cable could easily destroy some $1000 gears, all those cables would get replaced, and the Cobra's reputation would improve. Now you know, Mr. Elder. Perhaps OMC is at fault for not communicating this cable story to their dealers more effectively. If it's any consolation, Mr. Elder, I suspect the original owner spent enough money on depreciation to buy several gearsets. Boating is not a cheap hobby. I predict Mr. Elder's rebuilt Cobra will be trouble-free so long as his transom shift cable is OK (I assume that his dealer changed the cable when they installed his new gearset!). In my experience, the Cobra shift mechanism is the only weak point in an otherwise robust and intelligently-designed sterndrive. I also predict that many more Cobras will commit "cablecide" in the coming years. I urge all current Cobra owners to replace their "transom shift cable" if there is any doubt about its current condition. Happy Boating, Stuart E. Hastings stuart@hastings.org P.S. I got most of this story from Dan Gust and Tom Ski in OMC technical support. Trailer Boats should probably verify my version with OMC, and perhaps Mr. Elder's OMC dealer, before printing this letter. (copy of OMC form letter enclosed) (copy of Trailer Boats column enclosed)