Tohatsu M50D - oil leaking from water intake

[bertschb]

I have a 1995 Tohatsu M50D. I replaced the gear oil and a couple days later had the skeg replaced. When I got the boat home I thought I should open the top gearcase vent screw to let out pressure that built when the lower unit got hot from welding the skeg. The gear oil cavity was pressurized when I opened the drain plug. I should have cracked that plug open before the guy worked on the skeg. Oh well. <br /><br />Anyway, a couple days after the skeg was replaced I noticed oil leaking out the water intake "screens" on both sides of the lower unit. Not just a couple drips but more like a couple tablespoons.<br /><br />I thought maybe the heat from welding caused a gasket to fail? But, I was told there is no gasket to fail. Then I was told it might be 2 stroke oil leaking from the reservoir and running down inside the engine since I did top off the oil and had the motor tilted up. Another told me the gear case was cracked. I don't think it got cracked from the skeg repair.<br /><br />One more thing, the oil is no longer leaking. It dripped for a couple days and stopped. <br /><br />Any ideas on where the oil might be leaking from?

 

[pipe-Island-Chopes]

Re: Tohatsu M50D - oil leaking from water intake

I used to have that problem, i found that the only reason it dripped was because i have the fuel hose attatched onto the motor, is your fuel line attatched?

 

[bertschb]

Re: Tohatsu M50D - oil leaking from water intake

It's attached now. I don't think it was attached when it leaked though. Can't remember. How can that be related?

 

[pipe-Island-Chopes]

Re: Tohatsu M50D - oil leaking from water intake

It is probably normal,sarge. Two cycle engines just do that.The reason I say "probably normal" is you may want to check the lube. Get an oil dran pan,set it underneath the foot. Get 12oz tube of marine gear lube and two new screw gaskets (for the vent/fill screws).<br />Next, drain the contents into the pan. Observe the old lube's color and condition.It should be black or translucent green. If it looks like coffee with creamer, a gray milkshake, or visable water, it has a bad seal.<br />Run a finger thru the used oil in the pan,and feel for chunks of metal larger than a grain of sand.<br />If no chunks and the color is right,refill the lower unit,and use the new screw gaskets.<br />But otherwise, you are in good shape.

 

[TOHATSU GURU]

Re: Tohatsu M50D - oil leaking from water intake

There are two gaskets and lots of o-rings and seals that could fail due to heat. You need to pressure test the lower unit to determine if any of them are allowing oil out. It is unlikley that the two gaskets would fail as they would not normally be effected by welding on a fin. But, you also need to be aware that welding on a fin can cause the housing to warp and to "come out of round". That's why gear housings are always disassembled and placed in a cooling bath while they are welded.<br /><br />Gear oil is usually a golden amber and two-stroke oil is usually a blue, green or red. If what was dripping out was black that could be unburned two-stroke oil/carbon residue. If it was gear oil than the heat probably caused the driveshaft seals to fail.