Are you talking about Hose number 9 in this link?

http://www.perfprotech.com/store/ass...13832-180.aspx

If you are, Then that hose does not hook up to anything other then the impeller housing, The other end just goes up along the front of the engine and then aimed back down.

It may just be the drain tube you are refering to. If it is, I would maybe think a valve isn't closing completly. Allowing the air to escape and not build up pressure.

No it is not hose number 9. this hose is at the very back right side of the motor.

Its confusing to me too i didnt think there was anything else to the air system beside the green and white lines.

That whole system is confusing to me!

There are two hose #9's in that diagram. I bet it's the one hooked to #1 (actuator) in the diagram. That said, I don't know if that's really the problem. I swear when we had my friend's seawater pump out to replace the fitting for the white hose, I pumped up the line to make sure the new fitting was sealing. The new fitting was sealing but you could still feel some air coming out of the black drain line (#9) when I pumped it up. His system is working fine though.

i removed some of my system,,,because of stainless marine exhaust,,,,but when it was stock,,,i remember the water would come out of a quarter size rubber disc, when you pump it up,,,,the thump screw ( blue)type was to me used manually,,if the pump didnt work,,,so there must be a relive valve under there some where,,,youres rubber dics,,might be stuck open,,,the funny thing is i dont see listed on the merc parts sights,,,like bam,,,if your boat is in the water,,,and u pump air into the system,,,u will see where the water comes out,,,dont ask me how i know,,,lol,,,,just release the relief vales on top ,,,the one with the steel o ring on it,,,the water will stop filling up the bilge

Im thinking that the two #9 hoses connect somewhere. I know they need to be connected. On the top of the seapump where it connects there is a cylinder and a spring inside.Im thinking if im correct your motor drain's on both sides. I just did my sea pump and that line does connect to somewhere just not sure where. Runs along side the starbord side of the motor to the back. Can't get to my boat till Thursday. I can check then and let you know friday unless you fint it first.

thats what i remember seeing,,,its not on any parts manual???wonder why

That would be great, i wont be able to get mine until Sunday.

http://www.mercruiserparts.com/Show_...t%2C+863208A+3 it kinda looks like this,,,