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As my drive gets older, more and more quirks start to pop up. I have an 87 Alpha that is trailered and is not a stranger at all to regular maintenance. This year, the "stalling when shifting" is starting to be a nuisance. The cable is about 3 seasons old. I just had the drive off so I am well aware of the condition of all the shift parts (at least external to the drive). The cable seemed to be working fine- a little friction but you could still move it with one finger. I decided to approach the problem with a little bit of science. I devised a spring arrangement so I could get some idea of the forces involved. The force in the cable to over come the friction to shift a non moving drive was about 5 pounds. The force to actuate the cut out switch was about 15 pounds. So its takes 5 lb to move the cable and 15 to activate the switch so it should never cut out, right? (and it does work great on the trailer) Well of course it is not that simple! When the drive is running and there is load on the dogs it takes a lot more force to separate the dogs. The problem seems to be worse after the drive has been run at power (cruising speed). Obviously Mercruiser went to a lot of trouble to devise this cut out switch to make this thing work. So with all this said, can some one educate me with what is really going on. Is an extra pound of force in the cable that critical or is it that the dogs are wearing out and need to be replaced?
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I'm not sure how many pounds of force it takes to shift. With the drive installed, check to be sure that the brass shift lever is not bound against the bell housing shift shaft. You can also remove the drive and hand shift to see if the shift shaft pivots easily. Worn clutch dogs would let the unit come out of gear easier and when worn enough not stay in gear. In this case I would not suspect the clutch dogs.
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