Mercruiser – Fresh Water Drive Pump

As I have stated before, the lack of maintenance that can easily be performed astounds me when I am sometimes called to help out with a problem. Simple procedures can and will avoid costly mistakes. On the water this can go beyond the failure of a crafts mechanical systems and involve human lives. Ironically failures due occur in even the best of maintained equipment, however having done due diligence will ensure that you have done your best to avoid such issues and statistically will ensure a long and useful service life of your unit. I have even in my own boat have observed sand and fine debris when the boat has been near such materials. Many who beach their boats have found themselves with high engine temperatures as a result of clogged cooling systems. Keep in mind that this falls true in all crafts with all types of cooling regardless of fresh or closed water systems. However one system over the other might be more forgiving than the other, in any event they are all susceptible.

Simple as it is, it’s always advisable to run your engine before docking or loading if you are in good water and not in shallow depths.  Towing your unit is an ideal situation to run your engine out of the water and utilize a flushing device. Boats taken out of the water however are susceptible to dry out and thereby allows the materials like sand to cake up in the cooling system.

 

An important note: Never run your boat out of the water for any period of time without a sufficient supply of water drive, damage occurs even if you’re just turning the engine over. I have replaced countless pumps for owners that were just simply turning over the engine.

 

The impeller in your unit turns over when you turn over the engine, thus it can and will get to the point where I have replaced the entire pump housings that had become distorted due to temperatures. Impellers can become distorted and destroyed in less than 30 seconds, housings can distort from heat in minutes and you stand a good chance of destroying the seals in your outdrive. It is also prudent to remove your prop while running your engine out of the water. I have seen some disastrous results even with experienced mechanics as a result of becoming too comfortable with their trade so to speak "complacent" and in too much of a hurry, basically "Lazy" In either case accidents can and will happen, however working safe is a mindset and not an excuse for disaster.

 

Fresh water pump (In Drive): An impeller change with gasket kit is about $35.00 Bucks; an entire kit is around $80.00. On my own boat I change out the impeller every 2 or 3 seasons, depending on conditions and usage. As to the pump housing, I change this out every 4 or 5 seasons. Remember to torque the pump housing properly this goes a long way in providing ample supply of water to the engine. Leaks will get worse over time and debris and such can get onto and into surfaces that are not condusive to such materials. The kits all come with an array of gaskets for various applications. Take time to disassemble your unit and lay it out accordingly in order, as each gasket and piece comes apart. I often instruct owners to layout the pieces accordingly from left to right in a row, and then I have them lay out the new pieces underneath the old, in a row, matching each piece and gasket accordingly. Thus when you reassemble your pump there will be no question as to its accuracy. Another trick with the impeller into the housing is to lube it up and twist it in carefully while the lower pump housing is out of the drive, make sure that the blades are in the right direction, center it over the shaft and insert the impeller key on to the shaft, work the impeller to center and align with your key.

 

As always, I cannot stress the importance of obtaining a manual on your unit, obviously the best manuals are from the manufacture; however some information can be obtained on the internet. Everybody including myself has an opinion, but the factory has the last word.

 

INSERT PIC of Pump Disassembled: