Re: Help? Brass square screw attached to rubber line
What you seem to be describing is the rubber hose and brass (sometimes steel) fitting for the fuel and oil recirculation system from the airbox. The rubber hose is short and comes from the bottom of the airbox. The fitting should screw into the manifold below the bottom carb on the port side of the manifold. (left side of the engine, right side when looking at it from inside the boat) Or, it may be a press fit that has fallen out.
If the fitting itself is not screwed into the manifold, then either the threads have stripped and/or it has fallen out or the previous owner removed it (for whatever misguided reason---you would be surprised at the things people do to Force engines)
It needs to be replaced. If it is stripped or has fallen out for any reason, use a little JB epoxy after cleaning the fitting and hole free of oil residue. Be sure to use little enough epoxy to not clog the hole.
Explanation: The fitting itself has a metered hole in it so it will not affect operation whether it is recycling oil or open to air. Since each carb services only one cylinder, pulses of air, not a steady flow course through them. Also, since the reeds don't close immediately, there is always a little blow back and spitting of fuel and oil through the carbs. This fuel and oil mix collects in the bottom of the airbox where manifold vacuum sucks it out and back into the manifold to be delivered to the cylinders and burned. This system is an attempt to keep the inside of the engine hood from getting too oily and dirty.
If the fitting is not screwed into the hole, there is no metered orifice. The hole in the manifold will bleed excess air. the engine may run rough at idle, may idle rough or fast, and may run slightly lean at speed. The hose may be disconnected with no ill results because the fitting is metered, but the fitting MUST be screwed into the manifold hole or the hole must be plugged.
