It’s more than likely that your marine engine uses a raw water system to help keep itself cool. This system is simply a pump that pumps seawater to the engine to help diffuse some of the intense heat the engine generates.

A marine raw water pump is a very simple mechanism. So simple, in fact, that you probably won’t give it a second thought until it fails. This is an issue — if your engine overheats on the open water, it can create a very problematic situation.

For this reason, servicing the marine raw water pump at regular intervals is crucial. Fortunately, due to its simple design (all the pump really is a flexible impeller inside a housing), marine raw water pump maintenance is not that complicated. Here are the basic steps:

Marine Sea Water Pump Maintenance Steps

You should make a habit of checking the impeller on a regular basis. To do so, follow these steps:

1. With the thru-hull closed, unscrew the end cover screws and remove the cover and gasket. You can use a pair of needle-nose pliers to grab the hub of the impeller and pull it out.

2. If you’re struggling to free the impeller, remember that there’s also an impeller puller tool you can order for this purpose. Do not, under any circumstances, try to pry the impeller out with a screwdriver, as doing so will almost certainly damage the housing.

3. Carefully inspect the impeller. Look for any cracked vanes or vanes that are bent out of shape. They should be round. If any of the vanes are damaged, replace the impeller.

4. Assuming the impeller looks in good shape, return it to the housing. First, lubricate the inside of the housing with a light layer of petroleum jelly or some other lubricating grease. Then, lubricate the impeller with diluted dishwashing liquid before reinserting.

5. You may need to use a fresh gasket and/or cover when you’re reassembling.

6. If you’re replacing your impeller with a new one, be aware that different materials are used to make impellers. They can be made of neoprene, nitrile or polyurethane. For your purposes — a marine sea water engine cooling pump — you’ll want a neoprene impeller.

Contact Diesel Pro Power for Flexible Impellers and Other Vital Marine Engine Parts

Even with regular servicing, a marine sea water pump can fail, which is why it’s highly recommended that you keep an extra flexible impeller onboard your boat to swap in should your raw water pump fail at an inopportune time. If you need any parts for your marine water pump or any marine diesel engine component, you can order them directly from Hubei July.

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