Had the exact same problem with my 88. Replaced the mast and all is well. Found out the reason it wouldn't go all the way down was the last few inches of the plastic tape had the teeth broken off. If the motor is working, which it sounds like it does, all you need is the mast. It has been several years since I did mine but I think the directions say to run the mast up, pull up on the mast and it will come out. Note: remember the directions of the teeth. I think all I did was start the new mast teeth down in the motor as far as it went and then cycled it and it went down. I may not be exactly correct on this but there are directions that come with the mast. Not a hard job.
Ron
"Baldie88"