smile0784 wrote:skronkman wrote:It will not work. The impeller needs to be submerged to work correctly. It won't draw the water up the hose.
Is the impella near where the muffs go on?
The impeller sits on top of the gearbox, where the bottom section comes away from the mid section. In the picture above you can see the join between sections about 150mm above the muffs. When your boat is in the water at standstill the impeller is under water (should be!) and being lubricated by the water, when you start your engine the impeller forces water up into the motor. Now the pump (impeller) is primed it can continue to suck up water so that when you are on the plane the impeller is actually above the waterline but still working (if your motor height is setup correctly and trimmed properly the top of the water should be just coming over the top of the cav plate).
Having said that, I know my Mercury will self prime when launching from the trailer and I only just have the cav plate submerged, so a lift of about 100-150mm from dry but this is not good for the impeller as it starts up dry and unlubricated for a few seconds, shortening the life of it so it's not good practice.
The muffs would not form a very good seal to the lower section so as not to allow air in when trying to suck in the water that is not being forced in via a hose on a tap. The added length of the lift required for the hose length from an unprimed impeller would also unlikely work to start sucking up the water. Even if you did get a good seal and it did generate enough lift you would still be starting your impeller dry until it could bring the water up to itself which is not great.
In short, make sure your impeller is flooded before starting the engine, either by submerging it or forcing water into it under pressure (or using the dedicated washout port provided by the outboard according to the instructions provided with YOUR outboard motor as they are not all the same)