Hey Fellas, I have a 1967 Seafair Sedan with a merc 120 I/O that runs great, but every time I try to go into reverse, the outdrive doesn't seem to latch and the prop speed just lifts the outdrive out of the water, which as you can imagine makes the boat slightly more difficult to reverse. When the engine is off and I have it on the trailer, and I put it at about half throttle in reverse, it will eventually catch and holds the outdrive down, but it doesn't catch immediately when put into reverse, and of course any reverse power will lift the outdrive before it has a chance to latch by the time it will latch when not running. Is the a replacement part I need, or an adjustment that can be made? I'm half thinking that since it works in half throttle, it might be an adjustment that needs to be made? I'd sure love some of your knowledge and input! Thanks much!
Sounds like the reverse lock hooks are worn or not moving well enough for a solid engagement with the tilt pin. These older drives have a locking arrangement much like the outboards of the era, and are prone to wear. Take a good look at the mechanism while someone shifts the outdrive into reverse to see where the issue is, sometimes it is just a case of reshaping the worn hooks with a dremel tool. Remember to spin the prop by hand as the unit is shifted to allow clutch engagement.