Dima_NZ
Cadet
- Joined
- Dec 23, 2018
- Messages
- 26
Hi everyone. My first post here (although I've read plenty of great advice over the years).
Dima’s attempt at a short post to describe a long problem with a 1998 4.3L EFI and a 1988 Alpha 1 Gen 1 lower gear unit on a 1988 SeaRay Seville 18ft kept on a trailer.
Dima’s attempt at a short post to describe a long problem with a 1998 4.3L EFI and a 1988 Alpha 1 Gen 1 lower gear unit on a 1988 SeaRay Seville 18ft kept on a trailer.
- Engine dies shifting from neutral to reverse most shifts, even on driveway with earmuffs. If it ever makes it into reverse, shifts out to neutral just fine. Reason - shift interrupt hinge bracket thing flicks down as I try to go into reverse, and stays down - killing the engine (interestingly, I made a "loop" that I can plug in instead of the switch to bypass it - tested it with the loop out on the water shifting into neutral, knowing that I will need to use the ignition key to come OUT of gear, and it still kills the engine mechanically... but that's for another thread perhaps).
- 6” centre-to-centre cable adjustment procedure repeated multiple times as per manual #6, no impact
- Control cables checked and operate within tolerance in manual (80mm travel from WOT to WOT)
- Shifter cable is near new – pulled leg off, it operates super smoothly with no binding or resistance. Routed around the starboard exhaust riser, as per diagram. Nut threaded all the way into the bell housing. No salt build up, still greased up. No obvious water leaks. Bellows relatively new.
- Excessive play was recorded with shifter cable disconnected from shift bracket with prop locked in forward (travel of 18mm from interrupter-plate-starting-to-move to interrupter-plate-starting-to-move), spec says should be 14mm or less. I might have been pressing too hard, so might be within the 14mm after all. Went to investigate.
- With leg off (upper still bolted to lower), printed out that “degrees rotation” paper template and tested play in lower shift shaft as per instruction – got 12 degrees play exactly, which is right within spec. Shift spool in lower thus seems OK.
- The one thing we did notice (my friend Chris was helping), independently of each other, is how much RESISTANCE there is turning the lower shift shaft CCW to put the gearbox into reverse. From Neutral (say, 11 o’clock), I can use my pinky to turn the lower shift shaft to forward (towards 12 o’clock). But massive effort is needed to turn the lower-shift-shaft CCW towards 10 o’clock to go into reverse.
- To confirm what we felt, I built a tool (see attached two pictures) – I push the end of the metal ruler to change gears, and record how much flex there is before the lever starts turning. The metal ruler flexes around 2cm before the shaft starts turning if I’m shifting into FWD, but, it flexes around 6-8cm before it starts turning towards reverse.
- My theory is that this resistance of the lower shift shaft to turning CCW inside the lower unit is what’s causing the interrupt switch to engage when going into reverse. It can’t be anything else (I think…)
- My task is now to flush the lower unit a few times with diesel/kerosene/part oil to try and remove any gunk that may be binding the lower shift shaft. This could be all that’s needed. However, I’m not that hopeful. It may be that the internals of the lower gear unit are toasted.
- It doesn’t make sense to me why the resistance of rotating the lower shift shaft is so much greater CCW compared to CW rotation.
- Have I missed any troubleshooting checks?
- Assuming the lower gear unit is stuffed, do you recommend a rebuild, or, with a 1988 Alpha 1 – would I be better off buying a new lower gear unit?