lower unit leak

[Matt Locklear]

I have 1998 nitro 640lx with 98 Tracker Force by Mercury Outboard. On the top and bottom of the propeller base with the unit are two screws. The bottom seems to have a leak, minor leak. It appears that the gear fluid is coming from the screw at the bottom but could possibly be coming from the base of the prop with the foot. Through a period of about 24 hrs it leaked out about a quarter sized amount. Does anyone have any info or similar issues? Any help would be great. I think it is an o-ring, maybe a seal. I have check it out yet. I know it could be a number of things. I just dont want something small to become a major issue. Thanks for your help. I have pics of this as well and can send them if necessary.

 

[firedog978]

What you are describing sounds like the lower unit oil fill and drain holes. Two larger screws that are directly above and below one another. The lower one is for draining and filling, while the upper one is an overflow while re-filling. Both of these have gasket style washers. Each washer should be replaced with a new one when gear oil is changed.



A quarter size amount of oil doesn't sound like alot but, is enough to indicate a need to change oil and replace washers. I suspect the washer is bad. This should be done AT LEAST annually anyway. You absolutely do not want water getting in there! The washers are not expensive and can be gotten at almost any marine dealer. This is also a job that you can do yourself very easilly. It would take you less than 30 minutes. Needed items include: Screw driver, gear oil, new gasket style washers and a small pump with fitting for lower unit oil. All these can be gotten at your marine dealer for very little cost.



Here's a link to Bass Pro Shops lower unit pump:



http://www.basspro.com/webapp/wcs/stores/servlet/Product_10151_-1_10001_44827____SearchResults

 

[Bryan McDonough]

Check for water in the lower unit, if oil can get out Water can get in. Oil will be milky is water is present.

 

[Scott Hammer TOXIC]

If it still leaks, I'd take a hard look at you shaft seals. Pull your prop and look for fishing line. That is what usually causes them to leak.



TOXIC

 

[Berry Lindley]

If it is leaking gear oil you need to get it fixed. If you get water in there and trash your gears, you won't be very happy. I'm with Tox betting it is probably the shaft seal. It will cost you a little more than you are thinking to replace the seal, but will preserve your lower unit=very expensive. A good shop can pressure test and know pretty fast what is up. Your profile doesn't say where in TN you are, but there are some excellent shops in middle TN for sure.

 

[Dan J.]

Make sure that it's actually your lower unit leaking. Your carbs will hold fuel mix after leaving the lake and while trimmed up they will dribble out, usually leaving a tell-tail spot of oil on the lower unit and gearcase. (Very common and very normal on carb'ed two strokes.) Look for a oily trail down the engine and/or smell the residue found. Should be a gas smell to distinctly seperate the fuel or gear oil residue.