Sorry for the delayed post. At the Vancouver boat show a few months ago, I explained to a Yamaha technician my problem and showed him my pictures. Long story short, he agreed the new lower unit shaft should fit. Even if it meant filing the splines carefully to match up with the worn splines in...
I agree. I think the pictures help me eliminate that there is any sort of unseen obstruction. I have little experience here… so I also posted the pictures in case others with more experience noticed something I didn’t.
I like this idea. Thanks! I did take some pictures with a boroscope to try and see what’s going on up top. (Took me awhile to get it plus be back with the boat, hence the delay) I’ll attach pictures.
Thanks Matt. It does worry me a bit that I'm trying to line up splines that are slightly different. They *look* slightly wider to me (and are 1/64th of an inch different, though hard to measure with the micrometer I have) , but not sure how that can be given the new lower unit should be compatible.
Thanks stresspoint. I'm unsure why I'd need to rotate the flywheel, if I can rotate the driveshaft? Maybe I'm missing something here, but shouldn't rotating the driveshaft to align splines do that same thing? Especially on a Yamaha, where there is some wiggle room to line up shift shaft and...
Thanks for the reply. Here is what I'm confused about ... If I'm able to rotate the drive shaft while trying to slide up the lower unit, why would I need to rotate the flywheel at all? I shouldn't need to rotate both ... just one or the other ... is that correct?
I have thought about swapping shafts. The pain point is that I'll need to drill out the bearing case retaining nut, and probably the bearing case as its seized right into the lower unit. (tried lube and heat and force and no luck) I was hoping to avoid this by buying the lower unit I'm now...
Thanks, mickyryan. I'm not clear on what you mean to do? It gets "blocked" about an inch and a half from going all the way up ... which matches the length on the top splines on the drive shaft. To me, it means that even if i twist or spin the shaft, I still bump into a metal-on-metal problem and...
Thanks again for the people that took the time to suggest ideas. Spent more time with the engine this weekend… unfortunately still won’t go. I had a marine mechanic neighbour help and he is stumped also. He though there might be some slight damage to top of new shaft splines. We did some light...
Thanks, mickyryan. If I understand you correctly, the reason the old lower unit driveshaft will fit into the upper unit, is that perhaps the splines are damaged slightly, but damaged in the "right way" so that they still slide up into the upper and align? The consequence is that the new lower...
Thanks boscoe. I appreciate the help. I’m trying to eliminate items that could be causing the problem. I have a marine mechanic friend coming over tomorrow to give me a hand. I’ll post the outcome afterwards.
Thanks dingbat. May I ask where to go to try and determine if there are differences between those driveshaft part numbers? I used boats.net to look at the parts breakdown, and for the 2000 model year, they do list that the 75hp Yamaha lower unit is compatible. I also measured the shaft lengths...
