ok so this is a 90 omc 3.0 stern drive cobra, or how ever u feel like wording it. shes is not pulling water from the lower unit. the impeller in the rear is new, the timing is set, tune up is done. she just wont suck water up, i can flush water from inlet side of the impeller and push water from the engine side down but not the stern drive side up to the engine. is there a vavle somewhere on the transom that would prevent water from traveling if it were to get clogged