Onerheating Outboard Motor

See if we can all agree on this - overheating is caused by not enough volume of cold enough coolant (water) flowing over the heater (engine).

Causes for not enough flow:

#1) clogged water passages - scale, scum, mud, plastic bags, trash of all kinds may be clogging your water passages. This restricts the water pump ability to flow enough water through the engine. Higher RPM increases pump pressure and forces more water through the narrow passages.

#2) clogged water intakes - all of the above can clog the inlet to the pump and reduce or stop the pump lift/suction to pull water through the pump.

#3) worn water pump impeller. At low speed the impeller blades are designed to rub on the outside wall of the impeller housing. When the blades are worn, they do not press hard enough on the walls, or not on the walls at all, and the pump stalls against the head pressure of the engine.

#4) Combinations of above issues

When you slow from high to low engine speed do you see the telltale velocity fall off to just a trickle? This should not happen. The telltales on Suzikis are designed to spray off to one side so they can be seen from the helm position (if you don't have to high a transom). If you see a good spray at 2000 rpm and a trickle at idle, get the flow fixed before you end up with warped (insert name of expensive parts).

Or - just think and drive like the idiots at my marina - "No Wake Zone" to them means keep the hull out of the water. Who needs idle speed for that?