Personally, I used a half tank of 24:1 with stabilizer before putter her to bed for the winter. I figured a liberal oiling of the internals couldn't hurt. Also, when draining the lower unit oil I found that after it stopped draining I tilted the engine up and down a few times and drained out even more oil.
Winterizing may include rodent-proofing your boat and motor too, depending on where you store it. I had two 40 hp engines stored outside with covers over the engines. The engine with the cowl had a mouse nest in it in the spring. It crawled in through the air intake opening in the bottom engine cover. I now recommend closing the choke plates to keep vermin out.
Thanks Evinruder......Fortunately my carb has screens going across the intake by the choke. Funny about the mice though. Get some squirrel cages and you might add some powere...lol. My lube oil is a little milky. Is this something I should address in the downtime. Or is that big a deal?
Check the obvious first before dismantling the lower unit. New plug gaskets? Any signs of fishing line around the prop shaft? Any cracks in the lower unit case? If you answered, yes, no, no, then you might have to take the lower unit off and pressure test it. No more than 10 psi though or your seals will pop their lips out. I used a small compressor and dunked it in a big bucket of water. Look for air bubbles. I had a cracked case but you couldn't see it. Probably water froze in the bottom of the case. That's what happens when you don't change the oil before winter. Water settles out of the oil as it sits and freezes if you live in a cold climate. It's about $100 CDN for all seals and gaskets ($107 US), snicker, snicker. There has been a change in the seals on the drive shaft since original. I think these are below the water pump. Anyways, two seals replace the original one seal. Install one up and one down and fill the space between with grease.
Blue Bomb, fishing line around the prop shaft can damage the seal. Anything that gets wound around the shaft like ski ropes can damage the seal. Fishing line is so fine and strong that it can cut like a knife. Sounds like you had water in your lower unit mixing with the oil. You need to troubleshoot to find out where the water got in before you add new oil. If your boat sits in the water all season it's also a good idea to tilt the motor up out of the water when not in use.
