Numerous people have asked me why they have to have their Water Pumps changed at regular intervals.
Some of the things people say are things like "I've only done 20 or so hours since it was last done". Or "She's still pumping water from the tell tale, why do I need to change it?" When I ask when the last change was, it is generally more than 2 years ago.
There is nothing new about Water Pumps. They've been around ever since the first water cooled engine was designed and built. You've changed them when your engine overheated at speed and that was that.
Well, not any more...things have changed.
We all know the Water Pump is in there somewhere (right?) and we seem to think that as long as the tell tale is shooting water, all is well.
This is not the case.
Have you ever noticed how all of a sudden a tree you have had in your garden since it was a sapling, seems to have grown overnight? It has always been there, but because you see it all the time, you don't notice it getting bigger and bigger.
The same thing with the tell tale. You see it all the time and never notice it getting weaker and weaker, until one day you're running along and you get an alarm. How is this possible? The tell tale is still shooting water!
Somehow boat owners don't think it is necessary to go to the trouble (or expense) of replacing the water pumps on their engines at regular intervals.
Off course, there is the other scenario (as in the case of the impeller above) where you either run aground or pick up a plastic bag around the water intake, run the Water Pump dry and then just simply fry the impeller, and in a lot of cases, the housing too.
(See pictures here.) Whatever the case may be, I would like to share some information with you that would maybe make you think differently when next time you look at the water coming out of the tell tale hole.
Yamaha recommends replacing your Water Pump Every Year or 100 hours whichever comes first. Why is that? Do they just want to make money from selling parts? No, I don't think so.
Most people think that the tell tale is there to show that the water pump is working and that sufficient cooling water is running through the engine, keeping it at the temperature it is designed to run at. This off course is true as well, but in today's Electronic Fuel Injection (EFI) four strokes it goes deeper than that.
The water coming out of the tell tale hole runs through the fuel rail (from where the fuel goes into the injectors) in EFI Engines, cooling the fuel and minimizing vaporization.
In some engines the water is also used to cool the Regulator Rectifier, which converts AC current to DC to be stored in your batteries.
So, if your impeller has been working for 100 hours or been sitting in one position for a year (without you running the engine for a minute), it can not function the way it should. The amount of water flowing through the fuel rail and/or Regulator Rectifier is less than it should be and excessive heat is present in these parts.
If you look at an impeller that has been installed for a year, you will notice creases on the inside of the curved fins, much like the creases on the inside of your fingers if you curl them inwards. This means that the impeller is no longer pushing all the water it should as the mere shape of it allows the fins to spin without pumping. Makes sense?
Oh, and while I'm on the subject, when you do a Water Pump change, replace the complete Water Pump, not just the impeller. The other parts wear out as well.
If you have the work done by someone else, ask to see your old parts. Take a look at them and notice how much wear is on the plate or inside the cup, but mostly make sure that not only the impeller has been replaced.
I think this knowledge might make you look at the tell tale water a bit more carefully next time and I hope you will remember to have your Water Pump changed regularly.
If you have any questions please feel free to contact me on my email at johan@sandycovemarinesales.com or just stop here at Sandy Cove Marine Sales.
