Lower unit install mystery

[yammyskeet]

First off, I'm a newbie. All I have is my seloc manual which does a good job of explaining how to do a job, but doesn't tell about potential issues I may run into. I have an 03 ox66 250 and I'm trying to install a new lower unit. My problem is that my new lower unit gets stuck with about 1/4 of an inch left and won't go any furthur. I've retried over 10 times and everything is lined up, shaft, shift shaft, water,etc. I've read over all the past threads and have tried all the tricks, shift shaft in neutral, turn flywheel, etc. I even measured new unit with old one, everything matches. Any help, much appreciated.

[oldcobia]

If your drive shaft has an o-ring on it, that's probably what's holding it up. You might be able to bump it on up. Try installing without the o-ring and see how that works.

[jb123]

keep in mind you have to align drive shaft, shiftrod and water tube, THEN the align pins on lower unit

[yammyskeet]

When I took the old one off, I don't remember seeing an o ring. I'll go back and look for that.

[yammyskeet]

keep in mind you have to align drive shaft, shiftrod and water tube, THEN the align pins on lower unit

The drive shaft is align as I can feel the spline go in when I had another person move the flywheel, the shiftrod is also in and the water tube as well. I put a little bit of grease on the water tube just to make sure. The align pins are in place ready to go in. but can't push up that last quarter inch. I've tried forcing and shaking it, that didn't work.

[Bilge Rat]

Make sure you don't have a big glob of grease on the top of the drive shaft.

With the LU in as far as you have it now try trimming the motor all the way down. Now you can push the LU straight up.
This seems to help align everything. You are pushing the weight straight up instead of holding the weight up and trying to keep the shaft straight going in.

Trimming it down has helped on a few motors for me when they wanted to be stubborn.

[captainhark]

the shift shaft splines engage at about that distance, make sure unit is in neutral and hand control is in neutral,,,
I just had a concern with a rebuild unit that was one spline off on the shift shaft, would get to about a 1/4 inch of mating then stop, if I move the shift assembly would get them to engage but not in proper timing, took the unit back, they fixed it but never did give a good reason

[yammyskeet]

Thank you all for the advices so far. I will try it trimming the motor down. The manual mentions the glob of grease. It's hard to imagine grease being solid, but I will look into that as well.

[99yam40]

where did the new lower unit come from?
Are you sure the drive shaft is the same length as the old one?
and the splines are cut the same length?

Something has to be different if it will not go.
can you still try the old one to make sure there is not a problem with the spiles in power head?

[yammyskeet]

where did the new lower unit come from?
Are you sure the drive shaft is the same length as the old one?
and the splines are cut the same length?

Something has to be different if it will not go.
can you still try the old one to make sure there is not a problem with the spiles in power head?

I bought the new unit from SEI. My old unit was an SEI as well, with serial tags on the inside. I measured the main shaft and shift shaft, they all measure the same length. I didn't pay close attention to the spline count.

Some other info, the reason for the replacement is I did hit a rock and the prop shaft was bent. Enough to cause a noticable vibration at idle speed. The impact hit the shifter area(nose cone) and my shifting became harder. It still went into gear, but it wasn't smooth anymore. Would this do anything to the shift rod?

[99yam40]

like I said see if the old one goes up OK now.
That should tell you if there is a problem with the new one.

I said measure the length of the splines not how many there were

[Bilge Rat]

Grease, oil, water, etc. is incompressable.
Viscosity, coheasive and adheasive bonds inhibit it from flowing out between the splines to allow the shaft to fully enter.

Liquid can act solid, jump out the boat at 50mph. You bounce, skip and hurt.

Check the motor midsection for any old alignment pins stuck in the holes hitting the pins in the LU.

Check the shift shaft alignment marks, make sure the shaft is indexed in neutral with the cable in neutral.

[yammyskeet]

Thanks for all the advice. I tried it some more over the weekend and same results. I will be taking it to the shop and will share what the issue was.