Alpha One out drive shift linkage question

I have a 1990 Thundercraft 1660LS with an Alpha one outdrive (120 mercruiser mfg in 1989). I replaced the lower unit impeller and seals last season following the directions in my service manual. Everything checked out using my water muffs (and submerged in a half cut drum). Had a great time at the lake. However, after a couple of days of boating without issue I went to back off the dock. Put it in gear, reversed off, went to neutral, then right to forward and... nothing. Boat went no place. Pulled the boat out of the water and found that the shift fork had become disengaged (dropped down into the lower unit). With it dropped into the lower unit, I could turn it either way and engage the gears, so I centered it with the shifter set to neutral and pulled it up. It wouldn't stay in place, so I ended up securing it with stainless wire and everything worked as before. Off we went, normal useage for a couple of days like this. Boat hasn't been in water since.

When I had the unit apart I did not take anything apart on the shift shaft, although when I was assembling everything I did have trouble ensuring that I had it firmly engaged in gear as the manual stated when aligning the two halves. Still, I verified that it shifted (locked the prop) after I assembled it and that it worked fine.

I've reviewed the figures in my mercruiser manual and I don't see what would keep that in place. What am I missing? I would guess that if I split this again it would be obvious? I didn't notice anything the several times I had it up/down trying to get everything lined up, except that the shift shaft gave me fits (but I don't remember exactly what about that.)

New season coming up. Might only get a week in the water, but I want to be ready. I'm sure things will be fine as I have them, but I would rather make it right.

Thanks.

Re: Alpha One out drive shift linkage question

sounds to me like ya forgot to put the washer on top of the shift shaft in the lower.
item #50 from here..
w/o this washer. the shfit shaft in the upper isn't raised high enough to properly engage the shift shaft in the bell housing. it's a common mistake many folks make.

Re: Alpha One out drive shift linkage question

yep, the old shift shaft bushing cover washer claims another victim

you gotta at least drop the lower half of your drive to install it

don't feel bad, happens to everybody at some point

Re: Alpha One out drive shift linkage question

I suppose I could've "lost" that washer at some point during disassembly/assembly, if it fell off without my noticing it. I didn't specifically take it off the lower shift shaft. It doesn't appear from the parts description to be that thick where it would allow the intermediate shift shaft to drop clean out of the upper shaft yet, I'll take it as a plausible explanation and something to look for when I split it again.

I do appreciate the link to the parts book. that'll be big help in solving the mystery of what is the problem.

Thanks for the insight!

Re: Alpha One out drive shift linkage question

its not the thickness of the washer that keeps the shaft up high enough, its the o.d. of it

it sits on top of the bushing assy "covering" the seal area

it really serves two purposes, 1. keep the shift shaft up in the fork and 2. keep the bottom of the shift shaft from ruining the seal

once you take it apart and see how it all goes together it will make sense

Re: Alpha One out drive shift linkage question

Ziggy to the rescue with a photo again, right there in front of the pump on the lower shift shaft. http://www.google.com/imgres?um=1&h...w=192&start=0&ndsp=13&ved=1t:429,r:2,s:0,i:80 If at any time you turned the gearhousing over it probably just fell off. The only other possibility is that it is there and it is bent, in either case you need to drop the gearhousing to replace it.

Re: Alpha One out drive shift linkage question

Ah, knowing that the seal is "cupped" does explain where there is a place for the shaft to drop into. I'm guessing this washer just fell off, probably when I first pulled the unit, as I tipped it to get it away from the upper unit when I stood up with it. I then carried it the length of my shop to the vice where I did my work on the water pump, and I held it pretty much straight up. Never saw it, but then wasn't looking either.

I swept the floor since then and more than once where I park the boat, did the work, and I didn't find any stray washers. I wonder if it's lurking under the storage shelving behind the boat... where it rolled away and has been hiding out for the past year laughing at me when I walk by. Either that, or some big spider came strolling through my shop and picked it up and took it to albuquerque.

Thanks for the help. I'll tear into this and let you all know. This job should be much easier since everything has been apart within the last year (I probably shouldn't tell, but I've owned this boat since 1994, and to my knowlege I was the first to split that unit. I certainly got the luck er life out of that impeller)

Re: Alpha One out drive shift linkage question

Got 'er split apart, and yep, sure enough there wasn't a washer there. Using the parts link I was able to get a suitable replacement at the local hardware store that matched the dimensions given for that washer in the parts list. It's all back together waiting for some fresh gear lube.

Thanks all!

Next I'll have to tackle that "up" side of my throttle trim switch. I can't trim "up". "Down" is ok and the "trailer" button works ok. Figure switch is probably the culprit. 12volt test light or my DVOM will prove that out.

Re: Alpha One out drive shift linkage question

Rexalot said:

Got 'er split apart, and yep, sure enough there wasn't a washer there. Using the parts link I was able to get a suitable replacement at the local hardware store that matched the dimensions given for that washer in the parts list. It's all back together waiting for some fresh gear lube.

Thanks all!

Next I'll have to tackle that "up" side of my throttle trim switch (trims down with the throttle switch and will go up with the "trailer").

Click to expand...

Trim limit switch (and/or its wires). Most people just put a jumper in the trim harness and use the UP button to trim and tilt all the way up...