Re: 1971 mercury 1350 outboard
There's a vent and drain plug on the lower unit. Both located on the same side.<br /><br />The procedure is as follows: pull the drain plug first. That way the oil won't 'gush' out of the lower unit. Then pull the vent (upper) plug.<br /><br />To fill reverse the process and fill from the bottom (drain) plug until oil comes out of the upper (vent) plug. Reinstall the vent plug before removing oil source. Then replace drain plug and you're done.<br /><br />Use marine grade Hi-Vis gear oil. Cheapest I've found is at Wal-Mart for around $3/qt. You'll probably use less than 25 oz to fill. It's also a lot easier, as mentioned, to pump the oil in rather than trying to use squeeze bottles. Small hand pumps which fit in a quart or gallon bottle of gear lube are available at most auto parts stores.<br /><br />Regarding water in the oil, either driveshaft seals (under the water pump), or shift shaft seals are the likely culprits.<br /><br />Your 1350 has mild steel driveshaft which will corrode in the seal area, so if you find that to be true you'll have to use Speedi-Sleeves or equivalent (AKA Redi-Sleeve etc) to repair the damaged area. The very thin stainless sleeve is driven over the damaged area and provides a good, smooth surface for the seal to ride upon. <br /><br />Sleeving is the easiest and cheapest fix, otherwise you're tearing the lower unit apart to either weld-repair the driveshaft or replace (big bucks). At that point it'd probably be cheaper easier to buy a later-model lower unit with stainless driveshaft.<br /><br />I had a '79 lower unit with swept-back skeg design on my old '71 1350; it worked very well and looked great.<br /><br />Anyway, HTH and Have Fun with the Mercs.........ed
