2001 9.9 2-stroke - water in gear oil

My goal is to determine if I need to buy the bearing carrier removal tool and disassemble the gearcase or not. i.e. is the leak most likely under the water pump, or the prop shaft? I'm hoping to hear from someone familiar with this motor who can comment on common failure modes. Local shops won't touch it due to age.

It's a 2001 2-stroke 9.9 fresh water motor, there was some water in the gear oil. The lower unit came off super easy and looks to be in great shape, but I don't have a pressure tester to determine exactly where it's leaking. The water pump is probably 15 years old (my brothers motor) so the seals around the shift shaft and under the water pump could be leaking, is this a common failure? The prop shaft looks great, nothing obviously wrong and no gear oil on the shaft, but I realize that doesn't mean there's no problem. Can anyone say whether the prop shaft, or some other seal are common failure points on this motor?

Do you have a gear lube pump? If so, you can easily make a pressure tester. If not, you need a gear lube pump, as it makes changing the gear lube much easier.

To make the pressure tester, pull the hose off the gear lube pump, and attach it to a bicycle pump, or any other pump you have. You only need a couple of PSI.

Remove and stick the gearcase in water and pump it up. Watch for bubbles. Normally Mercs leak under the waterpump or the shift linkage bushing.

Chris1956 said:

Do you have a gear lube pump? If so, you can easily make a pressure tester. If not, you need a gear lube pump, as it makes changing the gear lube much easier.

To make the pressure tester, pull the hose off the gear lube pump, and attach it to a bicycle pump, or any other pump you have. You only need a couple of PSI.

Remove and stick the gearcase in water and pump it up. Watch for bubbles. Normally Mercs leak under the waterpump or the shift linkage bushing.

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Excellent idea, thank you I will do this! I definitely have the lube pump. Crossing my fingers it's under the water pump, I really don't feel like disassembling the gearcase.

MattFL said:

Excellent idea, thank you I will do this! I definitely have the lube pump. Crossing my fingers it's under the water pump, I really don't feel like disassembling the gearcase.

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What's the condition of your drain and vent screw gaskets. That's the easiest to fix and easiest to see in your pressurization and submerge testing.

On Chris' comments, you don't need to remove the rear bearing carrier nut to address either of those comments. Other thing is the other place you would have a leak would be the prop shaft. The prop shaft turns the gear ratio slower than the drive shaft upon which the water pump is mounted which reduces the opportunity for it to be the prop shaft seal.

The second reason is that the prop shaft seal on the engines I have maintained was actually 2 spring loaded rubber seals and are installed in opposite directions on the prop shaft...one direction is to keep the gear oil in the gear case, and the other direction to keep environmental water out of the gear case.

So, from where I'm sitting you have a slim chance of needed a bearing carrier removal tool. One other thought I just had is the fact that on an old Merc I had once, with the old gearbox design where a large (huge) spanner nut held the bearing carrier in place, I have fished out the seals from around the prop shaft using a small diameter drill bit and a hooked SS scribe.

On some of these ( I can't see the parts ) the prop thrust washer can be used to turn the bearing carrier.----Left hand thread.-----These lower units are not robust.----I recommend you take it apart for inspection / reseal with a complete kit.

Mark has suggested a possible leak around the propshaft. Pulling the bearing carrier is an ugly job. It might also signal a bad propshaft bearing. I would recommend the pressure test and see what is leaking.

Chris1956 said:

Mark has suggested a possible leak around the propshaft. Pulling the bearing carrier is an ugly job. It might also signal a bad propshaft bearing. I would recommend the pressure test and see what is leaking.

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I agree on the pressure test and a tub of water. I am the sort of person that doesn't fix it it it isn't broken (known to be broken...obviously broken). Going through the cost and trouble of ripping everything apart and hoping you get it all back together just to be doing it....probably without the instruments to ensure spacers where needed is an iffy thing for non professionals (like me) and a first time mechanic for some tasks (like me) and the mental stress and all that...........for what? I subscribe to KISS and its not the band. Has worked for me all my life with no regrets.

Did you BUY and install NEW O rings on both drain plugs ? I do. Stopped the milky oil.

cyclops222 said:

Did you BUY and install NEW O rings on both drain plugs ? I do. Stopped the milky oil.

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Well I suggested that......got no reply!!!!!!!! Last time I was buying some, they were blue, OEM, and were said to be better quality than original OEM seals. Never had one leak, just changed them anytime I drained the crankcase and refilled with new oil.