Oil Leak

[Vassago]

Good day folks, new to the forum and new to Mercury outboards. I'm 3 hrs into a new (to me) 4 stroke outboard, 2007 Mercury 75 hp. Great motor by all accounts, but today I got home and an oil leak greeted me on the garage floor. I snapped a photo of the source. Basically,its the seam where the lower unit disconnects, where the water pump probably is. Is this engine oil or bottom end oil at this height? It's fairly brown in color on the floor, making me suspect engine oil coming down.

I've just started my investigation and will look to the service manual for input, but thought I'd also cast this inquiry out to all you fine folks at the same time.

Any thoughts or input is welcomed and truly appreciated.

Thank you

 

[Texasmark]

Since you have a 4 stroke you can't say it's natural due to burning oil in the fuel as 2 strokes require. However, brown oil means water (homogenized) into the oil like would happen in the lower unit when it is leaking. Or, with the 4 stroker, if you are doing a lot of trolling, and slow speed operation where the engine doesn't get up to a high enough temp to burn the condensation out of the crankcase oil, you can "manufacture" oil and can overflow the sump and come out in the exhaust or wherever it can get out and yes it can be brown too.....since water is the culprit.

1. With the engine vertical (I presume) after the engine has been in that positon for half an hour or so, and not running, check the engine oil level with the dipstick. How full is it and what color is it. Then after sitting overnight, in the same position, slowly remove your lower unit drain screw (the one on the bottom of the gearcase) bulge in front of the prop) and check for water and check the color of the oil. If water comes out first there is your leak or if oil is brown or yellowish, rather than dark blue-black same thing.

Do the checks and come back

 

[Vassago]

My plot thickens.. I had a closer look at the source of the oil leak and it appeared to come from a small 1/8" port on the underside of the fin towards the transom, not the seam above it. I also examined the oil on the garage floor and it appeared to be bottom end fluid. So I dropped the bottom end to inspect the water pump and state of the gaskets. when I pulled off the bottom end off and slid the shaft out I noted some engine oil collecting on the top splines on the shaft. No engine oil rushed down the leg and when I peered up the cavity up the leg toward the motor nothing looked unusual, no evidence of any oil streaming down the inside where the long shaft goes..
When I disassembled the water pump on the workbench, I noted some greenish bottom end fluid around the pump casing which is likely the source of my leak. My plan tomorrow is to get a pump kit and fix that up.. ]

But here's where it gets interesting....

While tiding up, I noticed engine oil dripping from the drain holes on that litlle platform in front of the transom. when I looked closer there was approx 1/2 L of engine oil pooling against the transom and spilling out the drain. I traced the dripping oil from the socket on the underside of the motor where the the top of the splined shaft came out of the engine when I pulled the bottom end out. This explains the oil I observed on the splined end of the shaft. Now I'm trying to figure out what the hell's going on with all this leaking oil!!! ...When I pulled the bottom end, I had the motor in the full trim position (as high as it could go).. There is no mistaking it.. the engine is definintely engine oil and it appears to be coming from the area where the shaft came out of the bottom of the engine.

My wonder now if my engine has suffered some type of seal failure on the bottom side of the motor where the tall shaft connects in. Anyone have any thoughts or input? I just know i'm going to have a hard time sleeping tonight not knowing what's going on. My mind is racing with the idea the buy who sold me this boat knew there was a major issue...... ARGHH!!!!

 

[Texasmark]

That's what it looks like to me. Next question is why? I don't know. If none of the pro-mechanics on here don't jump on this, like Faztbullet for one and there are others, just answer your own post with the word Bump and hit return.

This will bump your question back to the top of the pile and someone will come in and help you.

I have an idea but can't get closure because I don't know if it's possible.......PO did a water pump repair and upon reinstalling the LU didn't get the splines lined up between the drive shaft and the crankshaft and forced the LU on up some distance and that ruptured the crankcase lower seal.