Missing Lubricant in Gearcase of Yamaha Motor

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Author Topic:   Missing Lubricant in Gearcase of Yamaha Motor

jstarzy posted 12-22-2008 11:35 PM ET (US)
[This thread was move to REPAIRS/MODS because it seeks advice on repairs. Please use REPAIRS/MODS for discussions on this topic--jimh]
This fall when replacing the [lubricating grease in the gear case of 2003 Yamaha 90-HP motor] I noticed about only [about] 10-ounces draining from the gearcase. The grease was in perfect condition, no water. The gearcase took a full quart [i.e., 32-ounces] to refill. There appears to be no leaks at the gearcase or seals. The washers on the upper and lower plugs seem fine. I have a plastic bag around the gearcase and there are no signs of grease in the bag now after about a month after the lubricant change.
Unfortunately, I hit a rock rather hard season before last that took a piece about the size of a half of a dime of the upper skeg off. It is very close to the drain plug at the bullet. I'm hoping it's not a crack, of course. Otherwise, the motor is in perfect shape with under 100 hours.
[Give me] any thoughts [about the discrepancy between the volume of grease removed and the volume of grease added to the gearcase]. Did the rock take out the unit? Seal? Washer? Plug? I'm stumped. I would think that if I cracked the lower unit, water would have leaked into the remaining oil? Can't find evidence of having penetrated the aluminum by eye.
Help [is] much appreciated. Jim.
The boat is a [1989] Montauk.
Tohsgib posted 12-23-2008 11:32 AM ET (US)
Run it a few times and check it again. You would see a crack. Remove prop and look for fishing line or [something] around lower seal.
Ridge Runner posted 12-23-2008 06:33 PM ET (US)
Best thing to do is to pressure check the lower unit.
Ridge Runner posted 12-23-2008 06:36 PM ET (US)
The process is you need a pressure tester with a gauge and a fitting that will thread into one of the plug holes. Remove the plugs and let the oil drain, if you haven't already. Put one of the plugs back in and thread the tool into the other hole, then pump it up until the gauge reads about 5 psi. Let it sit for a few minutes and watch/listen for leaks. If it holds at 5, pump it up to 10. Rotate the shafts and move the shift shaft; this can sometimes reveal leaks caused by a nick, scratch, or pitting in a shaft. If the gauge doesn't hold pressure, you can usually hear the leak and find it pretty easily. If it's a slow leak, try putting a little soapy water, or other liquid, around the seal areas and watch for bubbles. If your tool is capable of checking pressure and vacuum, repeat the above steps using vacuum. Generally, the pressure check is all you need, but occasionally back-to-back seal problems are easier to find with vacuum.
Chuck Tribolet posted 12-25-2008 10:05 AM ET (US)
Pressure test it a low PSI (like 1-2) also. Higher pressure
my seat the seals and stop the leak. A while back we had
someone with just that problem -- no leak at high pressure,
leak at low pressure. Remember that underway, there's about
zero pressure.
It's not uncommon for underwater cameras to leak in the
rinse tank when they were fine on the dive.

Chuck
jstarzy posted 06-24-2009 06:15 PM ET (US)
Closing the loose end here.......with help from a good friend with a garage full of organized parts and gadgets to die for....I tested the lower unit with a gauge we assembled from parts. I pumped up the lower unit to 3 lbs, waited 15 seconds and then went to 13lbs and waited 15 seconds. No leaks whatsoever.
So...it seems that a measuring the amount of lube drained from the lower unit will not lead to an accurate indication of lower unit leakage at all. Not sure why this is but the drain amount seems to be less than the capacity but no leaks were measured. I believe the capacity to be about 20oz. I drained less over a reasonable amount of time. I guess a Yamaha LU retains quite a bit of lube when draining during regular maintenance.
Thanks to everyone for their help and advice....I'm back on the water...!!!
Jim.
R T M posted 06-26-2009 08:07 AM ET (US)
Why is it not possible that the lower unit was not filled to capasity before the time you drained it and discovered the "loss" of fluid?
rich/Binkie
jimh posted 06-26-2009 09:51 AM ET (US)
If draining the gearcase produced only 10-ounces of grease, yet refilling the gearcase required 32-ounces of grease, the inference is that the gearcase was not completely full of grease prior to the draining process, and about 22-ounces were missing. I agree with your assessment that if grease could escape from the gearcase that water could enter it. The absence of any sign of water contamination is a reasonable indicator that the gearcase was not leaking. The simplest assumption is that the gearcase was not properly filled previously.

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Author	Topic: Missing Lubricant in Gearcase of Yamaha Motor
jstarzy	posted 12-22-2008 11:35 PM ET (US) [This thread was move to REPAIRS/MODS because it seeks advice on repairs. Please use REPAIRS/MODS for discussions on this topic--jimh] This fall when replacing the [lubricating grease in the gear case of 2003 Yamaha 90-HP motor] I noticed about only [about] 10-ounces draining from the gearcase. The grease was in perfect condition, no water. The gearcase took a full quart [i.e., 32-ounces] to refill. There appears to be no leaks at the gearcase or seals. The washers on the upper and lower plugs seem fine. I have a plastic bag around the gearcase and there are no signs of grease in the bag now after about a month after the lubricant change. Unfortunately, I hit a rock rather hard season before last that took a piece about the size of a half of a dime of the upper skeg off. It is very close to the drain plug at the bullet. I'm hoping it's not a crack, of course. Otherwise, the motor is in perfect shape with under 100 hours. [Give me] any thoughts [about the discrepancy between the volume of grease removed and the volume of grease added to the gearcase]. Did the rock take out the unit? Seal? Washer? Plug? I'm stumped. I would think that if I cracked the lower unit, water would have leaked into the remaining oil? Can't find evidence of having penetrated the aluminum by eye. Help [is] much appreciated. Jim. The boat is a [1989] Montauk.
Tohsgib	posted 12-23-2008 11:32 AM ET (US) Run it a few times and check it again. You would see a crack. Remove prop and look for fishing line or [something] around lower seal.
Ridge Runner	posted 12-23-2008 06:33 PM ET (US) Best thing to do is to pressure check the lower unit.
Ridge Runner	posted 12-23-2008 06:36 PM ET (US) The process is you need a pressure tester with a gauge and a fitting that will thread into one of the plug holes. Remove the plugs and let the oil drain, if you haven't already. Put one of the plugs back in and thread the tool into the other hole, then pump it up until the gauge reads about 5 psi. Let it sit for a few minutes and watch/listen for leaks. If it holds at 5, pump it up to 10. Rotate the shafts and move the shift shaft; this can sometimes reveal leaks caused by a nick, scratch, or pitting in a shaft. If the gauge doesn't hold pressure, you can usually hear the leak and find it pretty easily. If it's a slow leak, try putting a little soapy water, or other liquid, around the seal areas and watch for bubbles. If your tool is capable of checking pressure and vacuum, repeat the above steps using vacuum. Generally, the pressure check is all you need, but occasionally back-to-back seal problems are easier to find with vacuum.
Chuck Tribolet	posted 12-25-2008 10:05 AM ET (US) Pressure test it a low PSI (like 1-2) also. Higher pressure my seat the seals and stop the leak. A while back we had someone with just that problem -- no leak at high pressure, leak at low pressure. Remember that underway, there's about zero pressure. It's not uncommon for underwater cameras to leak in the rinse tank when they were fine on the dive. Chuck
jstarzy	posted 06-24-2009 06:15 PM ET (US) Closing the loose end here.......with help from a good friend with a garage full of organized parts and gadgets to die for....I tested the lower unit with a gauge we assembled from parts. I pumped up the lower unit to 3 lbs, waited 15 seconds and then went to 13lbs and waited 15 seconds. No leaks whatsoever. So...it seems that a measuring the amount of lube drained from the lower unit will not lead to an accurate indication of lower unit leakage at all. Not sure why this is but the drain amount seems to be less than the capacity but no leaks were measured. I believe the capacity to be about 20oz. I drained less over a reasonable amount of time. I guess a Yamaha LU retains quite a bit of lube when draining during regular maintenance. Thanks to everyone for their help and advice....I'm back on the water...!!! Jim.
R T M	posted 06-26-2009 08:07 AM ET (US) Why is it not possible that the lower unit was not filled to capasity before the time you drained it and discovered the "loss" of fluid? rich/Binkie
jimh	posted 06-26-2009 09:51 AM ET (US) If draining the gearcase produced only 10-ounces of grease, yet refilling the gearcase required 32-ounces of grease, the inference is that the gearcase was not completely full of grease prior to the draining process, and about 22-ounces were missing. I agree with your assessment that if grease could escape from the gearcase that water could enter it. The absence of any sign of water contamination is a reasonable indicator that the gearcase was not leaking. The simplest assumption is that the gearcase was not properly filled previously.