Lower unit leaky

The lower unit is leaking fluid out the little port just below where it bolts to the motor. Any idea what seal would have gone bad? My garage is heated, but the cold weather must crept in and froze some water somewhere.

that might be the drain hole for the water pump. rubber seals can contract in cold weather and allow some weeping. (Challenger Space Shuttle “o” ring failure in cold weather launch)If in heated space do a pressure test on the lower unit 55 – 70 degrees. if no leak your good. maybe just a slight seep when colder than what you would ever operate the boat in.

Would that cause it to leak lower unit fluid or water? I have not used the motor since November. I don’t have a way to pressure test it myself. It is leaking lower unit fluid that does not appear to have water mixed in. It is stii dark green.

Lower unit lube is usually more of a brown color, with 2 cycle oil being green. If that’s an oil injected motor that’s about where oil will drip if you have an oil injection line on the powerhead going bad.

Take the cover off the powerhead and wiggle the oil lines. One of them is probably cracked and brittle and will break if you tug on it.

A cheap fix. Just get some oil line from your Mercury dealer and some new clamps at Fleet Farm, etc. When changing oil lines it also doesn’t hurt to premix a little oil in your gas (say 100:1) until the oil lines have purged the air out of them.

Good luck.

Dan

The motor is 99 Mercury oil injected motor. I took the cover off and took a quick look around for leaks, but to be honest I’m not sure where the oil lines are for sure. Looking at the lines and hoses is like brain surgery to me. I did look at the fluid I put in the the lower unit and it is the same color as fluid that is leaking. It appears the engine oil is the same color too. I will most likely have to take it to a shop to diagnose.

Thanks for the replies guys.

The oil lines are just clear plastic tubing that’s about 5/16″ diameter. They will look “green” – the color of the oil that is in them. There are two lines on my motor and if yours is the same have BOTH lines replaced even if only one is leaking because the second one will fail soon.

Dripping oil in the garage is the good way to find that the lines have gone bad. If they break when you’re driving the boat the powerhead is toast. Even if they aren’t leaking and it’s something else, a ’99 is due for new lines anyway. My motor guy recommends changing the lines every 5 years.

Ok, thanks. I’ll take another look tonight to see if I can find anything. I’ve had the motor for 10 years. Maybe I am lucky the lines have started leaking before now.

First thing is smell the leaking substance, that will tell you where it’s coming from. If it smells burnt or gassy then that is just built up unburned oils that build up overtime in the exhaust. If it smells like new oil then you have a leak in your injection system.

I agree with changing the oil lines if they are old no matter what.

My smaller honda does that. Im getting water in the lower unit and in the winter when it freezes it pushes the oil up through a seal around the shift rod. From there the oil runs over to a similar hole, out and down the side of the lower unit.

Not to hard to drop those lower units. Just dont shift the gears while its apart. Make sure and change the water pump while its off if you havent done that. Got to remember to do that to my yamaha this spring.

Hey Mike, I took down the lower unit a few years back. It was a pain in the but getting the shift linkage back to the right spot. I left the shifter in the same gear, but had to move it to get the linkage back together.

I had the water pump changed last fall. I didn’t see any oil leaking in the engine compartment so I’m thinking it is something internal. It is still leaking a tablespoon of oil each day so I am thinking it is not the lower unit. When I talked to the shop they mentioned they were suprised I have gone 10 years with no leaks. Probably won’t get her in until February.

Found out today leaking fluid was fresh oil and gas mix from the upper part of the motor, not the lower unit gear oil. Bad check valve is the diagnosis. The guys at Boaters Outlet in Roseville seem very good to work with. Should be ready for the river soon.