Mercury 85hp O/B '77? Blue Band-Checking lower Unit gear Oil

[fomoco-gnatsum]

Hey I'm new to this boating thing! I bought this 16' Tri-hull Bowrider w/this motor on it. Was working great till a few days ago go to put it in drive , clunks and shakes? will run fine in reverse. I think its cables I tightened up the brass adjuster on the drive cable so the pull in too forward would be shorter, took up some slack (did this on land) But before I launch it again I want to check my fluid level (gear oil) with the motor trimmed vertical I removed the lower silver colored aluminum plug on the left side of the motor (facing the bow) but nothing came out? Is the black plug just behind it and above the filler? could not get this loose. The motor was winterized (I have the reciept) I can't locate any manuals so please help w/some info, I hope my lower unit insn't shot!

 

[tmcalavy]

Re: Mercury 85hp O/B '77? Blue Band-Checking lower Unit gear Oil

Your Merc is newer than mine, but sound like you pulled the Vent screw/plug. Unless they re-engineering the lower units between 73 and 77, the drain screw/plug is down on the gearcase...mine is on the left (facing bow and propeller) just about where the gear case and skeg (bottom fin) meet...follow the forward line of the skeg up to the round part of the lower unit (gear case) and the drain is right there. In any case, pull the drain plug first and have a pan/can under it. Then gently remove the upper plug/screw...once its out, oil will come out the drain hole. Should be honey-colored brown. If its like vanilla milkshake you have one or more seals letting water in the lower unit. A very bad thing. If oil is okay and you want to change it, let it drain out and then refill by pumping oil into drain hole until it comes out the vent hole. Then put the vent plug in, then the drain plug. Set to go.

 

[Kenny Bush]

Re: Mercury 85hp O/B '77? Blue Band-Checking lower Unit gear Oil

That screw is on the bottom, about the same hieght as the prop shaft/prop. Up higher near the cavitation plate is the fill screw, and to the right of that is the water pump drain screw(black). To check the fluid just pull the screw on bottom out and you should see a little trickle of oil come out. If you remove the fill screw up higher, it will make the oil come out faster due to the venting through the top screw. When filling with oil, pump it into the bottom hole until it comes out the top hole. Your oil should be brown in color whereas if it had a leak, that oil would look like a tub of melted bluebonnet margarine.