[macojoe]

I think they are all 3", but as long as it fits your hose or you buy the hose to fit it will be fine!!

You want the blower to suck the fumes out!! The fumes are havier then air and sink to the bottom of the bildge, this is why you need to get them out!

You should have some vent holes in the transom with clam shells on them? one should face forward and one to the rear. This is to blow in good air while under way and out the back. There is a third for the blower.