Kohler 5E Generator Raw Water Pump Impeller Removal and Installation
Changing the raw water pump impeller on a Kohler 5E marine generator is actually quite easy, as long as you can fit it in the small work area where the pump is. The generator is a closed system with a heat exchanger mounted on top of the generator. You will only need a few hand tools to do this job. A new impeller is available at your marina or local marine supply store.
You must first shut off the raw water supply at the hull fitting. Locate the pump, mine is mounted on the starboard side of the boat even with the waterline, yours might be on the opposite side. Remove the four 1/4″ bolts holding the pump to the generator. The only thing you really need to remove from the pump is the cover with the o-ring and then pull the old impeller out of the pump. You may have to slide to pump partially off the driveshaft and then back into position so the impeller sticks out a bit so you can grab it with your pliers.
If you have most of the impeller vanes on the old impeller, there’s no need to worry. If there are only a couple of vanes in the old impeller, it’s a good idea to flush the system with a garden hose to ensure there is good water flow and that most of the vanes are out of the system. Check the pump rotation by touching the start button on the generator control panel and note which direction the shaft has moved or if the impeller still has vanes, install the new impeller with the vanes rotating in the same direction.
The next thing to do is install the impeller in the pump. You should lubricate the impeller with petroleum jelly or liquid soap to facilitate installation and start-up. The easiest way to put the impeller on the pump is to pull the pump a little from the generator, place the impeller on top of the pump and rotate it in the correct direction to start (the tips of the vanes are dragging the rotation) and then align the impeller with the flat(s) on the impeller shaft and slide it into the pump body. After the impeller is installed, the O-ring should be placed in the groove of the pump casing with a little lubricant and the cover should be replaced with the bolts and tightened.
When the cap is in place and tight, it’s time to open the water inlet valve, checking for leaks. After everything looks good, it’s time to run the generator to make sure the whole system is working properly. There must be an ample supply of water coming from the exhaust port of the generator while the generator is running. This will become a normal annual maintenance job on your boat with normal use of the generator.
Sometimes these impellers will last a few years with just periodic use, but most will need to be changed annually if used frequently during the boating season. Different makes of boats will have the same type of system and are very close to this procedure. The only major difference might be the pump used in the generator, but it still shouldn’t be a big pump.
After first performing this maintenance item and becoming familiar with your boat, it should only take about 20 minutes to complete this task. The first time can be up to 90 minutes or so depending on what you will be studying, concentrating on, and observing.
This procedure was performed on a 2006 Searay 280DA with two Mercruiser 5.0 engines.