Water Pump Sticking On

[Jbx5]

Advice please.

The water pump on our boat is sticking on 50% of the time. Do I take the easy option and buy a new one or is there a cheaper / easy fix ? 
 

John 

[dom]

When you say sticking on, do you mean running indefinitely, or just longer than normal?

If it eventually turns itself off, it could be low pressure or a leaking diaphragm in the accumulator.

If it's intermittent, it's probably going to be the pump though. Not sure if you can service a modern diaphragm pump these days.

[Smoggy]

You can fit an inline pressure switch in the pipework after the pump so it cuts out when the right pressure is built, I assume it is getting to the right pressure.

Edit to add: Is there a leak somewhere that you haven't found yet keeping the pressure just below par?

[Jbx5]

1 minute ago, Smoggy said:

You can fit an inline pressure switch in the pipework after the pump so it cuts out when the right pressure is built, I assume it is getting to the right pressure.

Yes pressure ok 

[BroadAmbition]

What do you mean by 'Sticking On'? - Running constantly?

Has the expansion tank got the correct air pressure in it?

Griff

[Jbx5]

Yes pump not turning off sometimes. Not sure about the pressure in the tank. 

[BroadAmbition]

Aha - then it could be that the air pressure in the tank is low, (Or the diaphragm is split) needs some wind in it matey.

As a rough rule of thumb the air pressure in the expansion tank should be around half that of what the pump is rated at.  Hope this helps

Griff

[Pinto]

There should be a schrader valve on the accumulated (expansion tank) somewhere and the pressure can be measured in the same way as you would on a car tyre. Usually the pressure should be set 3-4 psi below the pump cut in pressure. 
Water been released from the schrader valve would indicate a split in the diaphragm.