Have you ever heard of a mercuirser motor that has to be primed with water before the cooling system will work

Question

I have a mercuirser 80 hspr in my boat. It is an older motor and for the water to curculate I must prime the system with water through an inlet mounted to the thermostat housing. Is this common?

Answer 1

I never seen this. Maybe the Impeller in the Lower Unit is bad and someone rigged this up, not knowing how to replace the impeller. The impeller is a small rubber star that pump water up to the engine. If, this is an Inboard engine it will also have a water pump on the engine like a car.

Answer 2

Even those old Renault powered 80's from the 1960's used a drive similar to modern Mercruisers with the same water pump - the system is self priming by design, so something is not right on yours. Advice above about inspecting the w/p impeller is spot on.

Answer 3

if you have to prime the system you most likely have an air leak in it somewhere allowing it to lose prime. Check the system, tighten any clamps and look for leaks in hoses etc. The lower unit impeller should be replaced yearly.

Answer 4

can't say i've seen this, but with an antique like that i would go with the flow.  have you checked the impeller?  hoses for blockage or holes?