1993 2-stroke Yamaha - gear oil through weep holes? - SailNet Community
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1993 2-stroke Yamaha - gear oil through weep holes?

Dear All,

It's been a long time since I worked on 2-strokes and it's showing!

This 1993 Yamaha 9.9 is new to me. When I examined the lower unit, I noticed that the housing just before the propeller was cracked. I replaced it, the bearings and all seals.

I then replaced the lower unit gear oil - when I did, not only did the oil come out of the top screw, but also out of two small holes, one on either side, just ahead of the top fill screw. So, after several attempts, I was able to get both top and bottom fill screws in and tight.

When I started the engine, gear oil was weeping from these holes. It has subsequently slowed, but it seems odd to me that any would come out.

So, is this a bad sign or is it normal? I am thinking that I may have to remove the entire lower unit and replace seals.

is there a .pdf manual available for this engine?

Thanks,

Chris
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Re: 1993 2-stroke Yamaha - gear oil through weep holes?

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Originally Posted by ccolton View Post
Dear All,

It's been a long time since I worked on 2-strokes and it's showing!

This 1993 Yamaha 9.9 is new to me. When I examined the lower unit, I noticed that the housing just before the propeller was cracked. I replaced it, the bearings and all seals.

I then replaced the lower unit gear oil - when I did, not only did the oil come out of the top screw, but also out of two small holes, one on either side, just ahead of the top fill screw. So, after several attempts, I was able to get both top and bottom fill screws in and tight.

When I started the engine, gear oil was weeping from these holes. It has subsequently slowed, but it seems odd to me that any would come out.

So, is this a bad sign or is it normal? I am thinking that I may have to remove the entire lower unit and replace seals.

is there a .pdf manual available for this engine?

Thanks,

Chris
Not famalier with your particular motor but the two small holes are probably water drain holes from the exhaust passages. The gear case should not be open to the water passages or the oil will become contaminated. When you replaced the housing perhaps a gasket is not properly placed or it masy be the wrong gasket. Maybe the lower unit was cracked from freezing and there is damage inside. Perhaps a Google search on Yamaha mlotors might turn up the manual you are looking for. Let us know what you find.

Paul T
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Re: 1993 2-stroke Yamaha - gear oil through weep holes?

Hi Paul,

What you suggest is what I suspect!

The weep holes are well above the area where I worked and what I did was very easy - I doubt they are related. I think I will need to remove the lower uint and see what's up...unless someone else here gives me a better prgnosis on the problem!

Thanks,

Chris
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Re: 1993 2-stroke Yamaha - gear oil through weep holes?

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Hi Paul,

What you suggest is what I suspect!

The weep holes are well above the area where I worked and what I did was very easy - I doubt they are related. I think I will need to remove the lower uint and see what's up...unless someone else here gives me a better prgnosis on the problem!

Thanks,

Chris
Forgot this, I had a 35HP Evinrude 2 stroke. After trolling for a long time and sitting on the trailer at home the weep holes used to have a black thick oil discharge come out of them. Probably a result of unburnt 2 stroke oil accumulating in the exhaust passages. If I ran it for a few minutes at full throttle before pulling out there was no discharge. If the oil you see is clean and looks just like the gear oil then you may have a cracked lower unit. Some pictures would help.

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Re: 1993 2-stroke Yamaha - gear oil through weep holes?

Hi Paul,

Thanks for your reply!

Here are the pics: not pretty! The first shows the engine lower unit in the water and the milky green lube that has seeped out. The second, I was alone, shows the engine lower unit with the engine partially raised. You can see the weep hole toward the front of the engine with milky green fluid seeping out.

Chris
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Re: 1993 2-stroke Yamaha - gear oil through weep holes?

NORMALLY if you service a lower unit you would do a pressure and vacuum test with a small hand pump similar to a brake bleeding tool


The seal rubber gets hard as it ages and the shafts will also grove in the seal contact area at some amount of hours

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Re: 1993 2-stroke Yamaha - gear oil through weep holes?

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Hi Paul,

Thanks for your reply!

Here are the pics: not pretty! The first shows the engine lower unit in the water and the milky green lube that has seeped out. The second, I was alone, shows the engine lower unit with the engine partially raised. You can see the weep hole toward the front of the engine with milky green fluid seeping out.

Chris
Definitely looks like gear oil that has mixed with water. Kind of hard to tell from the pictures but the upper part with oil seeming to come out of the steering post is a puzzle, it would have to travel upwards from the gearcase, not sure how. Maybe there is an exhaust leak, with cooling water in it, that is pressurizing the gear case and forcing the gear oil/ cooling water mix back into the inside and out at the steering post connection? As Tommays suggested if you can pressurize the gear case a little and watch for the pressure to drop that will indicate a leak into or out of the gearcase. Finding the leak may be another matter? All in all, it appears that either gear oil is escaping out of the gear case or being blown out?

Paul T
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Re: 1993 2-stroke Yamaha - gear oil through weep holes?

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Definitely looks like gear oil that has mixed with water. Kind of hard to tell from the pictures but the upper part with oil seeming to come out of the steering post is a puzzle, it would have to travel upwards from the gearcase, not sure how. Maybe there is an exhaust leak, with cooling water in it, that is pressurizing the gear case and forcing the gear oil/ cooling water mix back into the inside and out at the steering post connection? As Tommays suggested if you can pressurize the gear case a little and watch for the pressure to drop that will indicate a leak into or out of the gearcase. Finding the leak may be another matter? All in all, it appears that either gear oil is escaping out of the gear case or being blown out?

Paul T
This may be a stretch but maybe the gearcase is vented through a tube or passage up into the upper part of the lower unit or power head? If the seal between the water pump and the prop shaft is bad water may be forced into the gearcase resulting in the oil to be forced up and out the breather if there is one. In the motors I have worked on I was never aware of a gearcase vent but that is not to say there wasn't one. If you pressurize the gearcase and the oil flows out the steering post or weep holes it is either from a vent or a crack somewhere.

Paul T
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Re: 1993 2-stroke Yamaha - gear oil through weep holes?

Maybe this helps,

When I squeezed the gear lube containier to fill the resevoir, the expected happened; i.e., the lube came out the upper screw hole. The the unexpected; it also came out of the weep holes! Further, after screwing in the upper screw, which I thought would create a little vacuum, the lube came streaming out. It took me many trys to fill the resevoir.

The engine has not been run in 2-3 years - could it just be the oil seals in the lower uint - there are two more that I did not replace.

Thanks for all help.

Maybe time to take the lower unit off.

That won't happen until I finish with the diesel! Beginning to hate engines. I bought a sailboat, right?

Chris
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Re: 1993 2-stroke Yamaha - gear oil through weep holes?

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Maybe this helps,

When I squeezed the gear lube containier to fill the resevoir, the expected happened; i.e., the lube came out the upper screw hole. The the unexpected; it also came out of the weep holes! Further, after screwing in the upper screw, which I thought would create a little vacuum, the lube came streaming out. It took me many trys to fill the resevoir.

The engine has not been run in 2-3 years - could it just be the oil seals in the lower uint - there are two more that I did not replace.

Thanks for all help.

Maybe time to take the lower unit off.

That won't happen until I finish with the diesel! Beginning to hate engines. I bought a sailboat, right?

Chris
I sure seems that the gearcase is open to the atmosphere, somewhere. You mentioned a crack in the housing forward of the prop, any thoughts as to why it cracked, frozen from cold weather, impact, or other reasons? A good parts schematic may help before you open it up? Let us know what you find.

Paul T
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