95% water 5% gear oil in lower unit Merc 1500

[Zac Penn]

As I move along with this motor I am slowly starting to replace everything now that it runs good, cools good, and is pretty much water ready. Today I went to replace the gear oil and I think I am being generous when I say 5% gear oil.

I have already replaced the water pump but I did not buy the gasket/housing set when I did it. This is a new to me motor and I know it had sat without running for at least a couple years before I got it. I am sure I have caused some damage to the gears and bearings by running this way a few times, but luckily the water looked clean with no metal shavings to be found.

I am waiting out a rainstorm and then I am going to refill the lower unit with cheap gear oil from the hardware store, hook up the ear muffs and let it idle in gear for a few minutes and then drain the oil to see how much water intrusion I get from just the ear muffs.

If the oils looks good then I am going to refill it and then drop it in the water for a quick water test and then drain the fluid again to see how bad it is.

Seeing as how I am going to do this in two different tests...Will it tell me where my water intrusion is most likely coming from?

 

[Zac Penn]

No Title

Okay so after new fluid and running the motor at idle in forward and reverse for about 5 minutes I drained the oil and it is obvious there is water intrusion. The first picture shows what I think is a drain hole but it was draining water the whole time the motor was running. I don't know if that is right or not.

The last picture shows the 5 minute old gear oil that is very milky. Anyone have a good suggestion as to what is needed?

 

[Jhoppy]

It could, check that you have good gaskets on your drain and vent screws first, I would recommend however to make yourself up a lower unit pressure tester and find your leak that way. Find a fitting that screws into your lower unit, its 3/8-16 (i uses my gear oil pump adapter with Teflon tape on it to seal it) and put 10 lbs of pressure in it (i use a hand pump with gauge) it should hold pressure for a reasonable amount of time about 10 min without dropping at all. Then you can put some soap and water on your prop seal, drive shaft seal, shift shaft seal, drain plug, and pressure adapter to find you leak. Whith that much water it will be a good sized leak.

 

[Jhoppy]

It dose not take much water in gear oil to make it look milky, the only way to really measure the amount of water in there is to let the water and oil settle out in a clear container for a day or two, then you will know how much water you are taking on for sure. I'm not sure what that screw in the starboard side of the lower unit is for but i don't think it goes into the gear oil.

 

[Chris1956]

Well, the spots that oil can leak into the gearcase are the driveshaft seal, water pump base gasket, gearcase plugs, propshaft seal and shift shaft seal. The gearcase plugs, waterpump base gasket and driveshaft seal are easy to replace. I would recommend you start with those....

 

[Zac Penn]

Thank you so much for the help. Just to be certain I have the correct parts I am going to include links to the items you said were easy to replace...
Magnetic Drain Plug...
http://www.iboats.com/Sierra-Drain-...uctInfoContainer__Customer_Questions__Answers
Fill Plug...
http://www.iboats.com/Mry-Oil-Fill-...2657999--session_id.652151597--view_id.172763
I can't find these on Iboats but here are the Mercury part numbers...
Base gasket? 32438 Oil seal?31489
Oil Seal?31507

 

[Chris1956]

You likely just need the fill and drain plug washers. The gaskets, impeller and wearplate may be found (along with the plug gaskets) in a standard waterpump rebuild kit. Those kits service multiple models of motors, so match the base gasket to the waterpump base, and the wearplate gaskets to the water pump cover and base, respectively. Usually I recommend you buy a new waterpump base, rather than try to install new driveshaft seals in an old base. The price is real close....

 

[Zac Penn]

I went ahead and got the two oil seals that are pressed ingot he water pump base, replaced the base o-ring, and lower gasket. I also purchased new drain plug/gasket, vent/fill plug/gasket, flush plug/gasket, and the two upper water pump gaskets to hopefully eliminate the water pump all together. I am running it on the ear muffs right now and will then let it sit and drain the oil again to see if this fixed the problem.

If so then I will take it for a water test and see if the external water pressure trying to get into the lower unit is a problem. If so that leaves me with the shift shaft seal, and then all the seals on the propeller shaft to deal with.

Finger crossed I don't have to do those!

 

[Sea Rider]

Better test engine at open waters at speed for some hours, one thing is testing on muffs at very slow speeds other at plane speeds. You could have all lower leg or'rings, seals, gaskets way dried out, craked letting water into gear box through prop shaft. For peace of mind, better change water pump and lower leg parts that deals with water. Milky to me is when you have a Cappuccino exiting from gear box. Yours is slightly milky.

Happy Boating

 

[MTboatguy]

When I drained my oil a couple of weeks ago, it had water in it and it was dark brown, so a little bit of milk look is really not that bad of a leak, I replaced the drain and vent screw gaskets and have not had a problem since, I have run it probably 30 hours since the change in the lakes around here and changed the oil again last weekend, pure oil, no milk look at all.

 

[Zac Penn]

So I may still have a problem. I haven't had a chance to drop it in the water yet, but with the motor tilted all the way up I am having an oil leak from the lower unit. It is coming out of the weep hole right next to where the shift shaft is located (the lowest part of the motor because it is tilted up.

I was hoping I wouldn't have to drop the lower unit again but I guess i might as well and see where the oil leak is coming from. Seeing as how it is tilted I should be able to trace the oil trail up to the highest part and that is my leak.

I will update later.

 

[Zac Penn]

Sure enough it was leaking from the shift shaft bushing. I have removed it and will swing by the dealer tomorrow morning for a new one. I kept downward pressure on the shift shaft so that it wouldn't come out of the gear case, but it seems as though I can rotate it slightly under 360 degrees before it stops freely spinning. I had the motor shifted into forward gear before I dropped the lower unit so hopefully that is correct.

 

[Mi duckdown]

Was year and serial number mentioned?

 

[pro-crastinator]

Just wanted to share that the Marine grade gear oil is designed to still provide benefit when water gets into the mix.
... to a point. I thought your "milkshake" looked like mine did before it was re sealed, no damage done.

 

[Zac Penn]

Serial # 3755746

I have replaced the oil seal inside the shift shaft bushing and with the motor fully tilted up I am not getting any more oil leaking from the weeping hole. For now my upper water intrusion should be fixed. I am heading out on the water this weekend with some friends and when I get back I will drain the fluid and see what I got. I am currently just using cheap 80W90 automotive gear oil because i have been troubleshooting. I will switch to "Marine Grade" oil if, when I drain the oil after this weekend trip it is nice an water free. However if I need to replace more seals on the prop shaft then I will keep using the cheap stuff until I get it all worked out.

 

[Zac Penn]

Oh what a wonderful Tuesday it is!!!!!!!!!!!!!!!!! After a good 5 hours in the water this weekend I finally got around to draining the lower unit and I have nothing but pretty gear oil draining out. So I guess my worries are over for right now. I am going to head up tot he store to buy some "Marine" gear oil, even though I am not totally convoked it even matters, to fill it back up.

Thanks again for all the help.
Zac

 

[Mi duckdown]

use marine grade oil.