Upper and Lower Drain Plug Merc Sterndrive Alpha 1 Gen 1 Question

[1985 Century Mustang]

I'm replacing my gear oil and noticed the bottom drain plug has a yellow gasket, but the top doesn't have anything. Do both drain plugs use this yellow gasket or is it just for the bottom?.
Does a Gasket or O ring go on the upper drain plug too?

 

[Scott06]

I'm replacing my gear oil and noticed the bottom drain plug has a yellow gasket, but the top doesn't have anything. Do both drain plugs use this yellow gasket or is it just for the bottom?.
Does a Gasket or O ring go on the upper drain plug too?

Yes each one takes a gasket they sometimes can stick in the housing. I think the OEM merc ones are yellow now but they used to be blue fiber paper ones back in the day.

without a gasket you will get water in the gear oil

 

[JASinIL2006]

Yes, both should have a gasket and the same gasket type can be used. I like the Sierra gaskets for this application.

 

[1985 Century Mustang]

Thanks, my upper plug didn't appear to have a gasket, as I was getting some water in the gear oil. To make sure I got all the water out, I did 2 separate gear oil changes. The Second one I used a 50% alcohol flush, and it appears that all the water is out of the lower section. The first oil change I did, still showed a lil milky gear oil after the 1st change. Looks good now ... I just ordered 10 gaskets for $4.59 with Amazon prime, no brainer. Appreciate the input guys.

 

[Scott06]

Thanks, my upper plug didn't appear to have a gasket, as I was getting some water in the gear oil. To make sure I got all the water out, I did 2 separate gear oil changes. The Second one I used a 50% alcohol flush, and it appears that all the water is out of the lower section. The first oil change I did, still showed a lil milky gear oil after the 1st change. Looks good now ... I just ordered 10 gaskets for $4.59 with Amazon prime, no brainer. Appreciate the input guys.

Can always flush with kerosene or diesel

pressure test it don’t just assume it was the missing washer

 

[nola mike]

As @Scott06 said, check for a stuck gasket. I'd guess that without that gasket you'd get much more than a bit of water in the oil

 

[1985 Century Mustang]

Can always flush with kerosene or diesel

pressure test it don’t just assume it was the missing washer

I ran the outdrive on ear muffs for 10 minutes or so. I didn't see any water in the gear oil. But I agree a pressure test will have to be performed. Thanks

 

[1985 Century Mustang]

As @Scott06 said, check for a stuck gasket. I'd guess that without that gasket you'd get much more than a bit of water in the oil

I did get a fair amount of water in the lower gear oil. It took me two flushes to finally get rid of the water. So I'll keep an eye on it with the new gasket plug. I did replace the upper and lower oil seals in the beginning of the year. But anything is possible I suppose. I'm gonna do a vacuum test at the end of the month. I only use my boat now maybe once a week here in the East Coast as temps are getting cooler for boating. So I'm definitely going to monitor the gear oil when I get back in from boating.

 

[brian3127]

I ran the outdrive on ear muffs for 10 minutes or so. I didn't see any water in the gear oil. But I agree a pressure test will have to be performed. Thanks

the gaskets on the screws seals the screws for when the outdrive is submerged in the water you wont get water in the outdrive through the screws using muffs

 

[1985 Century Mustang]

the gaskets on the screws seals the screws for when the outdrive is submerged in the water you wont get water in the outdrive through the screws using muffs

I agree. But if the oil and or shaft seals, etc were shot I would still get water with the muffs on? I'm just trying to isolate the water issue right now, so far no water in the lower unit with the muffs on.

 

[Scott06]

I agree. But if the oil and or shaft seals, etc were shot I would still get water with the muffs on? I'm just trying to isolate the water issue right now, so far no water in the lower unit with the muffs on.

No running on the muffs will not show if any of the oil seals are leaking water into the gear case.

Only way to tell is to take drive off , drain, and pressure test. There is a ton of info in the stickies and threads here on how to build a pressure tester and run the test.

 

[1985 Century Mustang]

No running on the muffs will not show if any of the oil seals are leaking water into the gear case.

Only way to tell is to take drive off , drain, and pressure test. There is a ton of info in the stickies and threads here on how to build a pressure tester and run the test.

Thanks. I'm gonna take the boat out for an hour or so and check for water in the top cap.. I really don't want to remove the outdrive, especially because I'll be closing it up for the winter soon. Next year I'll do the vacuum test and inspect/replace the seals etc if necessary.

 

[Scott06]

Thanks. I'm gonna take the boat out for an hour or so and check for water in the top cap.. I really don't want to remove the outdrive, especially because I'll be closing it up for the winter soon. Next year I'll do the vacuum test and inspect/replace the seals etc if necessary.

Don’t waste your time.take the outdrive off for the winter do the pressure test at your leisure over the winter.

last fall when i went up to take the boat out, put boat in water off the hoist, saw an oil slick. my boat have never lost any gear lube… gear lube Is an inch low. Had fishing line on propshaft seal.
when I saw that brought drive home with me and spent jan into feb resealing my drive. Had time to pressure test , get parts needed, pressure test, get more parts needed etc ready to go in spring