'00 Merc 50HP Tiller Oil Issue

[mtgrates]

Anyone have an idea why oil would be coming through the carbs(especially the lowest carb) while the boat has been sitting for a period of time? The boat has not been used recently and has been sitting outside. I've had it covered with the motor tilted slightly with the trailer motor support in place. I recently noticed oil coming out through the transom and running down the back of the boat. Because I couldn't take it, I removed the oil reservoir expecting to find a hose leaking. No such luck. Neither the sensor or the hose are leaking. After removing the air vent cap on the top of the reservoir, there was a rubber "nipple"(or 'duck bill') that shot out like a missle. Should that duck bill cause the pressure to release and not build? Could that pressure build up in the reservoir force the oil through the oil pump and carbs? Why would that pressure build like that? Any direction in this matter would be great appreciated!

[boats.net]

There is a check valve on most models where the oil line connects to fuel pump, check it.

[TMD]

You might try this.

Remove the oil pump and see if there is oil leaking from the seal where its shaft goes through.

http://www.themarinedoctor.com/cgi-bin/YaBB.pl
TMD