Yamaha F100 TLRY - 2 lower units but only one shaft fits?

[westcoastrib]

Remove spark plugs, rotate flywheel while inserting drive shaft until lower splines line up with oil pump drive.

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?

 

[stresspoint]

from description ? .the shaft is locating fine to the oil pump but not the crankshaft .
as has been posted you may need to rotate the flywheel to aid alignment .
what's interesting is that the old shaft goes home but the new one does not .and that you can get the new one in but it seizes.

have you tried out of curiosity removing the water pump just to be sure nothing is hanging up there.(its probably not but just to cover bases)

also try some engine oil on the shaft to lube the splines , work the shaft in and out to see if it goes further each time you push it up .(disclaimer , I know how that reads but the best i can describe my suggestion) .

 

[westcoastrib]

from description ? .the shaft is locating fine to the oil pump but not the crankshaft .
as has been posted you may need to rotate the flywheel to aid alignment .
what's interesting is that the old shaft goes home but the new one does not .and that you can get the new one in but it seizes.

have you tried out of curiosity removing the water pump just to be sure nothing is hanging up there.(its probably not but just to cover bases)

also try some engine oil on the shaft to lube the splines , work the shaft in and out to see if it goes further each time you push it up .(disclaimer , I know how that reads but the best i can describe my suggestion) .

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 water pump. (not that I'm even getting that far) I haven't tried removing the waterpump, because I'm nearly certain it's not quite getting that far yet.

To clarify, the old driveshaft does in fact go home and line up with no problem. The whole reason for this repair and switch out from the old lower unit, is that the old lower unit has a problem in the gearcase. I'll have to drill out the gearcase to take a look, but no matter what gear I put the old lower unit driveshaft in (F, R or N), it will not translate power from the prop shaft to the drive shaft.

I have used marine grease to try and work the shaft, many, many times (ha ha), but no luck.

My next step is to try and get a scope camera to look what I'm dealing with for the flywheel splines. If that doesn't help, I may just have to bite the bullet and swap driveshafts.

 

[westcoastrib]

Not sure on your motor but I have swapped driveshafts in lower units where the top is different but the bottom was the same.

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.

 

[boscoe99]

It is an installation error.

 

[mickyryan]

when in doubt mic it with a dial caliper hell you could even use a poor mans mic, a crescent wrench would tell you , i highly doubt its different size and still feel its alignment but ill stop beating dead horse and watch

 

[saltchuckmatt]

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.

Is the one that goes in a different taper at the top?

 

[dingbat]

Grab a big glob of putty of some sort. Plumber's putty works well.

Roll it up into a ball and smash it down on the top of the shaft a 1/4" or so. Deep enough to get a good impression of the splines with the taper.

Now try the impression on the other shaft.

If you can't visually see a difference, line the splines up and smash the putty to get an impression of the fit.

 

[stresspoint]

the oil pump and the crankshaft are independent of one and other , if the shaft fits the oil pump which it appears it does ? then it should fit the crankshaft .
clicking the motor whilst pushing upward on the drive once the oil pump is engaged it should locate the splines to the crankshaft without fail.

 

[99yam40]

the oil pump and the crankshaft are independent of one and other , if the shaft fits the oil pump which it appears it does ? then it should fit the crankshaft .
clicking the motor whilst pushing upward on the drive once the oil pump is engaged it should locate the splines to the crankshaft without fail.

if that is true, why is it only the new shaft has the problem?
I am not sure how many times he has tried putting the old back up there, but he said it goes with no problem

 

[stresspoint]

if that is true, why is it only the new shaft has the problem?
I am not sure how many times he has tried putting the old back up there, but he said it goes with no problem

this is what i am intrigued about as well , the oil pump may not be engaging .

at this point ,i would get a dye marker and paint the splines and see if the shaft is in fact being engaged into the oil pump or not .
same applies to the shift shaft splines .

some thing is stopping the newly acquired gearbox going home we just need to eliminate possibility's.
as we are trying to do this without having our head in the motor to look and see what's going on it is educated guess work. ,

 

[westcoastrib]

Is the one that goes in a different taper at the top?

Same taper it looks like to me.

 

[westcoastrib]

Grab a big glob of putty of some sort. Plumber's putty works well.

Roll it up into a ball and smash it down on the top of the shaft a 1/4" or so. Deep enough to get a good impression of the splines with the taper.

Now try the impression on the other shaft.

If you can't visually see a difference, line the splines up and smash the putty to get an impression of the fit.

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.

 

[westcoastrib]

this is what i am intrigued about as well , the oil pump may not be engaging .

at this point ,i would get a dye marker and paint the splines and see if the shaft is in fact being engaged into the oil pump or not .
same applies to the shift shaft splines .

some thing is stopping the newly acquired gearbox going home we just need to eliminate possibility's.
as we are trying to do this without having our head in the motor to look and see what's going on it is educated guess work. ,

Tried to “put my head in motor” by using a boroscope. I haven’t carefully looked at pics yet. I’m not giving up on this thing!

 

[saltchuckmatt]

At the end of the day do the pictures actually help?

Not sure they do.

 

[westcoastrib]

At the end of the day do the pictures actually help?

Not sure they do.

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.

 

[westcoastrib]

if that is true, why is it only the new shaft has the problem?
I am not sure how many times he has tried putting the old back up there, but he said it goes with no problem

I have successfully put the old shaft in about a dozen times.

 

[westcoastrib]

Tried to “put my head in motor” by using a boroscope. I haven’t carefully looked at pics yet. I’m not giving up on this thing!

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 the power head. As of last week, it worked! Took the boat out the last few days and everything seems to be working fine. Just wanted to post a final follow up and again thank all who replied.