Raw water pump: rebuild or replace?

Stu Davies

PBO reader Clive Hathway has a leaking raw water pump. Should he buy a replacement or rebuild it? Stu Davies gives his advice

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I have a Moody 27 with a Volvo Penta MD2 engine. The raw water pump is leaking.

Where can I find a replacement pump?

Clive Hathway

Stu Davies replies:

This particular pump can be rebuilt quite easily – indeed it’s the norm to do so – so no need to spend lots of money on a new one.

There are two ways to do it.

Source a rebuild kit for around £65 from somewhere like www.coastalrides.co.uk. Or source just the bearings and seals from a firm like www.simplybearings.co.uk.

Measure the bearings or get the number off the side of the old ones and measure the size of the old seals and specify stainless steel springs for the seal lips.

Changing the parts in the pump is quite easy. You’ll need a pair of circlip pliers plus a few other hand tools.

With the pump off the engine, the circlip holding the plastic gear needs to be removed first. The circlip is all that holds the gear in place.

Once that is off there’s another circlip holding the bearings in the bronze housing. That needs removing.

Continues below…

Turning the pump over, the flat impeller plate needs to be removed along with the impeller.

Behind that is where you’ll find the offending leaking seal which can be CAREFULLY picked out with a small screwdriver or suchlike in between the edge of the seal and the bronze housing, so as not to damage the housing. The seal can then be flicked out.

Clive’s pump has two in the housing with the lips of one seal facing the impeller and the other facing the bearings.

The second one will need to be removed in a similar manner. Always remember that with lip seals, the spring and lips face the ‘pressure’ side.

The shaft and bearings can then be tapped out towards the gear side and the bearings carefully pulled off.

A two-legged puller might be needed but judicious use of a hammer to tap them off is also possible.

Mark the shaft before removing the bearings to show their position. The shaft can usually be polished up nicely with some very fine abrasive paper.

Reverse the order to re-assemble. Use silicone grease to prelube the seals.

The bearings are lubricated from the gear side by the engine oil.

Stu adds: In his original email, Clive says that his engine is an MD2. I struggled to find a parts diagram for the MD2 pump that matched his pictures, but we later found the part number for his pump which was actually for an MD2002 pump. However, the advice stands – it’s still better to rebuild a water pump than buy a new one if you can.

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