Unsure if Right Repair Manual?

[viking80]

Currently own a 1998 FORCE Mercury Marine 50HP Outboard (2 stroke) Motor. I recently have purchased a SELCO FORCE 1984-99 Repair Manual, in order to understand how to give the lower unit a lube before placing in water this spring. However, book's outboard motor maintenance section, doesn't add up. Just trying to figure out if I should have invested in a Mercury manual? Book shows two screws side by side. Lower unit has vent screw (marked) at top and similiar lower screw (unmarked) -- however I do not want to remove this screw if it will drop inside shaft. No other screws (even one that book mentions could be on back of bottom - hexagon in nature). New to the boating world. Thanks anyone.

 

[steelespike]

Re: Unsure if Right Repair Manual?

Can't speak for the Force. but most drain and vent screws are usually broad flat screws with a slotted head.
Screws that shouldn't be removed are usually smaller Phillips head.

 

[bradleeson]

Re: Unsure if Right Repair Manual?

I really think that the pivot screw is your screw that is adjacent to your propeller. right under that is your drain screw, and the vent screw should be the one up top that is the front of the two screws in series you mentioned.

 

[Frank Acampora]

Re: Unsure if Right Repair Manual?

The shift pivot screw will be a 1/4 X 20 slotted screw. This screw will be about 3/8 head diameter. It will be either in the side of the gearcase torpedo or just directly above it.

The vent screw will be a slotted head flat 3/8 X16 screw only about 3/8 long. It will be above the cavitation plate yet below the gearcase parting line.

The drain will be a similar flat screw located on the side of the skeg just up against the bottom of the gearcase torpedo.

If you accidentally start to unscrew the incorrect screw, ie. shift pivot, the threads are only about 1/4 inch long and the rest of the 1 1/2 inch screw is plain--no threads. If you only withdraw it about 1/2 inch and see the unthreaded portion, just slide it back in; nothing will have moved.

To change the oil, with the engine vertical, you remove both screws and drain old fluid, checking for abrasive grit, metal shavings and liquid water or milky oil. Any of these conditions bears further investigation. Assuming the old oil is acceptable. using a tube of oil or a pump, squirt oil in the lower hole until it comes out the top one. Replace the top plug just snug to prevent new oil from running out freely. Quickly remove the tube nozzle and replace the bottom plug. wait 1/2 hour for any possible entrained air to rise then again with the nozzle in the bottom hole, top off the oil until it again runs out the top hole. Now replace both plugs as before and tighten very firmly. Here, tighter is better.