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Mikes Mobile Marine LLC

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Tip #3 Water Pump Service

Hello, I’m Mike owner and operator of Mike’s Mobile Marine here in beautiful Brainerd MN.

Today on Mikes Mobile Minute I will be talking about the most important maintenance item on your marine engine short of its lubrication. This is an item that if not serviced regularly can cause major damage to your engine.

If you’ve ever been a boat owner I’m sure you have heard of the water pump impeller. The water pump impeller is the life blood of your engine and is responsible for the delivery of cooling water to the engine. Now while there are other items and reasons for engine overheat, the water pump impeller is most susceptible to abuse and needs regular servicing.

The water pump impeller is a rubber veined pump component that is designed to draw water in from the hose, lake, river or sea to your engine with the purpose of removing excess engine heat away.

Outboard engines have their water pumps located in the gear cases while I/O’s will have them either in the out drive or mounted to the front of the engine.

Most marine engine manufactures recommendations on servicing the water pump are similar at one to two years time.

The reason for this is the rubber impeller blades will get stiff and not be able to develop the proper water presure. When this happens parts of the engine block will start to heat up. You may look at the witness water trail (the pee stream) and think it looks good or feels cool but this is not an accurate test. You see low water pressure from the pump also provides less water to the engine leaving cooling cavities full of air (generally at the top of the block around the #1 cylinder) and hot spot in the engine. Over a short period of time, the overheated areas, generally the exhaust side of the piston, because this is where most the heat is, will grow and start the scoring process of aluminum transfer to the cylinder walls. This can take a little bit of time or can happen all at once.

A high percentage of the engine rebuilds I perform are because of the lack of water pump servicing.

My recommendation and a good rule of thumb is to service your water pump every two years unless the engine has had an issue with overheat, lack of water to the engine while cranking or running (like dry cranking/running, running in sand, weeds or other like obstructions to the gear case water pickups)as this can cause a premature failure of your water pumps. If any of these are a concern service before next use.

Remember that the rubber veined impeller needs water to lubricate and extend its life. I never recommend dry cranking or running even though there have been some manufactures stating with their product this can be done short term only. I wouldn’t take the chance.

I also recommend if at all possible, servicing the water pump in the spring time. This gives you the extra advantage of a fresh impeller without the added wear sitting six or more months before its first summers use.

Stop by for additional money saving tips.  
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