Cobra SX lower unit drain plug will not open

[ggundersen3]

I have a 1995 Four Winns 190 Horizon with a Volvo Penta Cobra SX stern drive. I bought it at the end of last season. I had the engine winterized with -100F marine antifreeze but could not open the drain screw at the bottom of the lower unit to check for any water as the screw is just simply too tight to open with a screwdriver. I unscrewed and checked the dipstick at the top of the lower unit and the gear oil looked perfectly clean. I still want to open that screw however. Thinking of using a flathead screwdriver socket so I have leverage to get it to loosen. The boat is in unheated indoor storage which I have easy access to and we're getting daytime temps in the 30's here. 2 questions here: Is there any danger in exerting some force in opening that drain screw in cold weather? Is it bad to lower and raise the stern drive with the trim and tilt in cold weather?

 

[alldodge]

No issue with either
Have you tried a impact screw driver, the one that you use a hammer?

 

[Horigan]

I had the same issue on my Cobra SX. I used an impact gun and 1/2” drive flat head screw driver socket to loosen it. Make sure the driver socket is new (sharp edges) and it’s full flush in the screw when you use the impact gun. I bought a larger than needed driver and filed/ground it down to fit the slot.

 

[BRICH1260]

I second the hammer powered impact driver. Make sure to get the widest bit possible.

 

[ggundersen3]

Problem solved. Thanks for the advice. I bought a 3/8 drive(see attachment) socket with a flathead screwdriver and it opened it right away. Just needed the extra leverage. Good news also is pure gear oil flowed out, no water. All good! Thanks again!

 

[bruceb58]

Make sure you replace the o-rings on all 3 plugs everytime you change your gear oil.

 

[ggundersen3]

Make sure you replace the o-rings on all 3 plugs everytime you change your gear oil.

Yes thanks! I always do replace all the o-rings with new ones.

 

[jerryjerry05]

Don't necessarily need an impact driver.
A small propane torch and a BFS does the trick.