Cannot get Lower Unit back on - 2016 Yamaha 6hp

I decided to do a full service on a new to me 2016 Yamaha F6SMHA. It has seen some salt water but not too bad.
It was a bit hard to get the lower Unit separated but once apart looked pretty good. When I try to get it back installed I for some reason cannot get the driveshaft splines to fit back into the power head.
I have a piece of ready rod the same diameter and I can get it to fit in but no matter what I try I cannot get the driveshaft back into the power head.
I’ve done dozens of Johnson’s and Evinrudes but this is the first Yamaha.
What am I missing ?
Thanks !!

Turn it upside down.....

So empty out the engine oil first ?
I was told oil will get into the cylinders if the leg is higher than the power head.

Yes, drain the oil first and also drain the carb of gas. I have had similar problems with small HP outboards. Turning them upside down makes it much easier. First take a flashlight to see exactly how the driveshaft fits in. The shift rod linkage is also a pain on those motors.

Yep drain er if a 4 stroke

faztbullet said:

Turn it upside down.....

Click to expand...

Wow, that was the ticket. Thank you.
Once I hooked up the shift linkage I turned it upside down and 2 mins later it was in.
Much appreciated.
Gravity is my friend !!

What does turning the motor upside down do to help?

I’m not sure tbh, I know it’s a pain but with a strong small torch, I find it just as easy to refit it the way it came off, it’s defo a fag about but I’ve personally not needed to drain the oil and invert the engine yet.