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Fleet Admiral
- Joined
- Mar 25, 2001
- Messages
- 8,217
Lower units are transmissions, just like a manual car transmission, only it has one set gear ratio.<br />It is one of the most overlooked areas of routine maintainence on outboard engines...That is, if the reported problems with them here, are indicative of the number of boaters who find out the hard way, they have overlooked it.<br /><br />It's important to drain and inspect the lower unit frequently,at least once a season. Check your owner's manual for the reccommended intervals, and lube type.<br />Most outboards use "Outboard Gear Lube"..This is very simular to Hypoid gear lube, but has addtives to keep foaming down,and allow water to suspend in the lube better. This adds just a bit of protection after contamination, but not much.<br />There are, of course. (synthetic and fossil variations),as well as other exceptions to the specified requirements, so DO consult the operators' manual for type and capacity.<br /><br />You will need a handfull of rags, and some hand cleaner (like GoJo, ZEP, LAVA among others).<br />To inspect your lower unit, the boat must be out of the water,trimmed down. You will need an impact driver and a hammer.<br />You will need enough replacenment lube to refill the unit with, in a squeeze bottle or pumpable container. You'll need a drain pan.<br />You'll need new VENT/FILL screw gaskets. These are cheap, costing less than 2.50 for 5 of them...Note, they don't don't sell 6 in these packs?!?!!? Don't tell me THAT isn't calculated by some bean-counter somewhere! <br />But do not skip these gaskets, or else there is no need to even start this job. I prommise, sooner or later, the re-used gasket WILL leak.<br />Get the oil drain pan, and place it under the skeg.<br />An impact Driver is THE tool of choice for this next step..I wouldn't try it without one,and they only cost between 10-15 dollars U.S.<br />On the side of most lower units, there is a screw labled "VENT" and "FILL". Both of these screws need to be removed by turning counter clockwise.<br /><br />INSPECTING THE LUBE ;<br /><br />Once all the lube has drained out of the L/U, observe the color and quanity of the old lube.<br />It should be very close to the right amount for your lower unit,as outlined in the specs.<br />It should be black, or dark,translucent green.<br />If it is peanut butter or gray colored, or if there are any streaks, you have water contamination. Now, take a finger and run it thru the old lube, feeling for chunks of metal. Any chunks are not good. If you see the real fine powder-sized flecks suspended in the lube, it should be considered normal..Chunks, or grains larger than a grain of sand,and you have gear damage.<br />If you find a lower than normal amount of lube, or water in the unit, you have one or more bad seals.<br />IF YOUR INSPECTION PASSED: <br />Clean all signs of old screw gasket from the VENT/FILL screws,and the surfaces that they come in contact with around the holes.<br />Place a new gasket on both clean screws. Place them somewhere you can grab them with ONE HAND,to get them started in thier holes.<br /><br />Now this is the "trick" part... You must fill the unit by the LOWER HOLE ("Fill"), until it comes-out of the top hole ("VENT").<br />When it comes out the top, you must grab the VENT screw, and start it into the VENT hole, while at the same time, holding the lube bottle or pump tbe in the FILL hole. Do not remove it until you have the vent screw threaded into the VENT hole.<br />Have the FILL screw in your free hand. In one movement, reinstall the FILL screw,and tighten. <br />Yes, some lube will leak back out, but not much more than a few drops (if you are fast enough).<br />Yes, it IS messy, so I hope your rags are handy.<br />Tighten the screws to specified torque.<br />If you don't have the specs, you can tighten it hand-tight with the impact wrench,and then two or three whacks with the hammer, to tighten a bit more than hand-tight, but not so much that you strip them.<br /><br />I HAVE ONE OR MORE BAD SEALS...NOW WHAT?<br /><br />It could've been nothing more than a leaking VENT/FILL screw gasket, so refill the L/U with fresh lube, install new gaskets on the vent/fill screws, and take it out for the day.<br />When you get it home, re-drain and inspect the color. If it is clean,chances are better than good, gaskets were the culprit,especially if the screws initially were too easy to remove.<br />If it has been re-contaminated, you just wasted 4dollars, but now you know, you have seal problems.<br />The most common seal to fail is the propshaft seal. Stuff wraps-up around the prop shaft, and wears out the seal. Sometimes, lube will actually drip down the skeg, and show up as a spot on the driveway. Other times, not.<br />At any rate, it's time to pressure/vaccum test the L/U. This will require an air fitting that will fit the VENT screw hole, an bicycle tire pump with gauge, or compressor with gauge for pressure-testing, and a vaccum pump with gauge to vaccum test.<br />Many times, only a pressure test is required to find the leaking seal(s). Drain the unit, and install the fiting into the VENT hole. Make sure the FILL screw is in and tight. With the L/U submerged in a garbage can (Yes, this can usually be done engine-mounted), charge the L/U with 5-10PSI air pressure NO MORE, and look for a stream of air bubbles. They will escape from the propshaft area. or the water intake, or you may find a hairline crack.<br />But whatever,where there are bubbles, there is a bad seal. You'll have to have the shop manual to procede. You'll have to drop the L/U according to the shop manual. Order an impeller and lower unit seal kit.<br />Of course if the "2-cycle snake bites you" , help is a post away.<br />Good luck.
