Needs some ideas on this one guys. A 1999 Evinrude 15 4 stroke. engine over heats in neutral and reverse after 20 minuetes or so of idling. It has a new water pump complete with housing. The engine idle RPM are aove base idle spec. in forward it will run all day, but in rev and neutral it will tapper off on water flow and get hot. It is mounted plenty deep in the water. Engine is used as a kicker.