Lower Unit Oil Leak-1966 Johnson 9.5 HP

[beeeman]

I'm new to outboards but very mechanically inclined. I have a 1966 Johnson 9.5 HP, model #MQ-12A, 2 stroke. When the motor is running, oil leaks out where the lower unit mounts to the main body. I removed the 4 mounting bolts and could only drop the lower unit by about 3/4 inch to inspect. No oil seems to drip out of the exhaust duct as much as where the lower unit meets the main body. I removed the drain plug and a milky mixture pours out, indicating an oil and water mixture. I have several questions:<br /><br />1. Where would the oil leak come from?<br />2. What does the "oil level" plug do?<br />3. Where do I add oil for the lower unit?<br />4. Does the motor itself require oil, other than the 2-stroke oil added to the fuel?<br />5. Are there any illustrations and/or theory of operation articles that would help me understand how an outboard motor works, both online and published books.<br /><br />Sorry for the very basic questions, but like I said, I am new at outboards. However, I'm very interested in learning about them because I'm meticulous about my engine work (cars,ATVs,lawn equipment, and now boat)<br /><br />Thanks in advance,<br /><br />beeeman

 

[Paul Moir]

Re: Lower Unit Oil Leak-1966 Johnson 9.5 HP

Outboards have Lower Unit oil, since there is a transmission & shaft direction change in there.<br />To change L/U Oil:<br />1) Set engine upright somewhere.<br />2) Remove oil level/vent screw.<br />3) Place small bucket under the L/U to catch oil.<br />4) Remove bottom _SLOT_ screw. Not the Phillips!!<br />5) Let old oil run out. Look for metal chunks. Oil should be honey (if new) or black (if old) and always smelly. If it looks like old coffee, or a bunch of water comes out then you have a lower unit oil leak.<br />6) Replace with new L/U oil (like gear/rear differential oil) available at outboard dealerships & elsewhere. Get new L/U fill screw seals while your at it. <br />7) With the engine upright, fill the L/U from the fill screw hole (bottom) until oil runs out the vent screw (the L/U oil bottle is made to do this). <br />8) Install the vent screw w/ new seal. <br />9) Remove Bottle. <br />10) Install Fill screw w/ new seal.<br /><br />Since you do have a real L/U oil leak, suspect the shaft seal for the driveshaft, located under the water pump. It could also be the shift rod seal. Purchase a L/U seal kit and replace all the seals. Sierra (aftermarket) P/N 18-2682 is your seal kit. It's available at NAPA and various web places. You might want a new impeller for the water pump while you've got the L/U apart (P/N 18-3003).<br />Also purchase a repair manual (available here, preferably the Seloc). You will thank yourself. Theroy is included with the Seloc one. They ought to come with the engine's they are so useful.<br />Hope this helps!

 

[dkondelik]

Re: Lower Unit Oil Leak-1966 Johnson 9.5 HP

'mornin' beeman,<br /><br />at the gap between the leg and the foot (lower unit), look closely and you should see your drive shaft and the "Shift-shaft-coupler". the shift-shaft-coupler is the little brass clamp with two screws in it. loosen/remove the bottom screw and the lower unit should drop off (complete with drive shaft). <br /><br />Paul Moir gave good advise. getting a service manual is critical if you plan on working on your ob.<br /><br />word of caution. when tightening the screw(s) in to the shift-shaft-coupler, BE CAREFUL. remember, this brass is a soft metal and will easily strip-out<br /><br />Good Luck<br />HAVVE FUN