Johnson 50hp Lower Unit Gear Oil Question

I'm new to boating so excuse my question if too dumb. Last year I bought a Triumph 17DC with a 1998 Johnson 50hp (J50TSLECC). The dealer checked everything before I bought the boat. I used it last season and everything was ok. This year, before attempting to hit the water for the first time, I decided to start the outboard in a large tub of water with the boat still on the trailer. I removed the prop so I didn't chance destroying anything. It started fine and ran it at idle for about 15 minutes.

Questions: (1) there was some black oil floating on the top of the water - is that normal? (2) how would I check to see if the lower unit gear oil level is ok?

I guess my fear is that the black oil was leaking from the lower unit with the prop removed.

Thanks, novice in Maine

John

Re: Johnson 50hp Lower Unit Gear Oil Question

The black oil is almost certainly just partly burnt oil from the fuel and is normal for 2 strokes

You should annually routinely change your gearcase oil.

Identify two broad slotted head screws on the gear case. Remove those and allow the oil to drain # 6 and #10 in THIS DIAGRAM

DO NOT touch other smaller screws in the area (#3 and #55) as they hold internal gubbins in place.

The oil should drain "clear and bright" if all is well. Any water or even milkiness indicates water ingress and the cause must be identified and rectified.

Fill with new oil via the bottom hole until it flows from the top one using oil in squeezy tubes or with a pump. Replace the top screw then quickly replace the bottom one.

New seals should be used. It appears that your motor has an O ring on the top screw and a flat nylon washer on the bottom one.