broken driveshaft on outboard

[frozen toes]

HELP!!!! I have a 73ish 25 hp Evinrude that has been eating the driveshafts. I have broken 2 this season so far. The first time the shear pin didn't give and broke the shaft at the splines that go into the lower unit gears. Had a new shaft machined. Now over the weekend it also broke. Is there something else that could be wore that would cause this? At $140, new shafts are getting expensive. Also, I seem to always have very milky lower unit lube. Maybe I am not getting everything sealed when I put the new shaft in? I just sealed the bottom cover the last time I changed shafts. Any help would be greatly appreciated. Thanks.

[Valv]

3 possibilities:

#1 You are shifting with motor still at higher RPMs than idle, wait until motor stops or gets to idle speed before shifting gears.

or

#2 Your lower unit bearings are bad due to water intrusion, thus tend to freeze up

or

#3 Second driveshaft wasn't machined with proper grade steel.