Lower unit Question

[MichaelMullis]

I have a 1959, 35hp. I changed oil in the lower unit a couple of weeks ago. Ran boat for about two hours at lake on CH. eve,drained oil on friday.When I loosend plug I was surprised to hear, and feel, pressurized air escaping.I have never noticed pressure here before so this has me wondering if I may have a problem that I don't know about. Also my oil had gone from clear looking to chocolate milk. I think that I may have gotten some water in here but the oil is not white/creamy looking so I don't think it was much, but any is to much in my thinking. I saved the oil in a bottle to take to a shop but thought that I would ask opinions here first.<br />1) pressurized lower unit<br />2) chocolate looking oil,not milky/creamy<br />Should there be any type of seal/gasket where lower unit bolts up?<br />Does this motor have a thermistat for cooling system? After I got home from lake I ran moter for about 30min. on muffs and at first when it was running it was not peeing out of top exhaust hole. I noticed this and kept checking head for heat. Just as head was getting to hot to touch, (and I was getting worried, about to shut off motor for fear of damage), water started coming out of pee hole and it seemed to cool down. When I shut motor off I saw a lot of watery oil coming out of lower unit drain hole under cavitation plate, this was like white milk.<br />Thanks for any advice.<br />Michael

 

[Joe Reeves]

Re: Lower unit Question

The surfaces where the lower unit meets the long exhaust housing is strictly a metal to metal surface. A bead of Sealer 1000 can be applied there if you prefer though but it's not necessary.<br /><br />It does sound like you have a leakage problem. Drain the unit, then apply 7 to 12 pounds of pressurized air to one of the screw holes (drain or oil level). If a leak exists, you should be able to see and hear it.

 

[R.Johnson]

Re: Lower unit Question

I'm confused here! That engine used a hose adapter that clamped around the exhaust outlet, that contained the water pick-up screen. Where were you able to use muff's, and run the engine for 30 minutes? Also it sounds like you have a upper drive shaft seal leaking. These older engines with there single seals are not the easyist thing to keep water tight.

 

[MichaelMullis]

Re: Lower unit Question

R. Johnson, this motor has a screen on the side of the lower unit that ties into the water pickup inlet/exhaust outlet that is above prop. I would like to have one of the types that hook onto the exhaust/intake stub. I think that that would allow more water to go to motor but I have not been able to find one. I had one years ago, but do not know what happened to it. I like them better then the muffs. But, you use what you have, and all I have now is the muffs.

 

[R.Johnson]

Re: Lower unit Question

Without the proper adapter, I would run the engine in some type of container, such as you might find at Wal-Mart. Your engine is up in age where it may be hard to seal again'st water intrusion. These engines only have one seal meant to hold the oil in. I would bet that on your engine you probably have quite a wear groove where the upper drive shaft seal rides. This depends on how many hours the engine has, and wether or not the gear case is bent. A bent gear case is not uncommon on these older engines. I live in the midwest where most engines are run on rivers, and rivers can give you a nasty surprize. Check your upper drive shaft seal, and check for wear. On this age engine, I would replace the seal, and keep an eye on the oil condition after every use.

 

[BillP]

Re: Lower unit Question

Water will separate out of the lower unit lube within a few hours. If your sample doesn't divide into water on the bottom and oil on the top (just like salad dressing!) you don't have water in the gearcase.<br /><br />If you have water, like posted already, the upper drive shaft seal (under the water pump) is a good place to look for leaks. Older omc motors had chrome on the drive shaft seal surface and the chrome can pit...expecially in saltwater. Water also sits on that seal and leaves hard mineral deposits on the seal. Those occurances wear seals and let the water pump push water down into the gearcase.