kohler 7.3 impeller change

[mjk1040]

Would area of boating have a relative effect on these impellers? Here in my boating area I'm hearing a 5 year impeller change! Any preference in manufacture of these impellers? Don't get me wrong I'm all about preventative maintenance, but also a believer in, if it ain't broken, don't fix it too. When afloat I am always watching my temp and oil gauges no matter what rpm's I'm running. As a matter of fact I'm always checking the gauges even when the admiral is operating the helm, and bestowing on her to be mindful of these two gauges on each engine when she's piloting the boat. Mike

[Viper]

Qr BbpostWould area of boating have a relative effect on these impellers?...

Absolutely. Anything in the water passes through those impellers so murky sediment laden water wears the impeller a lot faster than clean water. Boating habits also contribute. If you do a lot of shallow water boating, your props will stir up sand that gets sucked into the intakes and blast the impellers.

Qr Bbpost....I'm all about preventative maintenance, but also a believer in, if it ain't broken, don't fix it too....

While this is acceptable for some systems, impellers is one that if you do wait until it's broken, you could be stranded. Also consider that by the time you see a change in temps at your engine gage due to an impeller failure, your exhaust temp has already shot through the roof. Typical cause of early exhaust hose failure. It only takes seconds before exhaust temps rise to critical levels without water. Engine temps on the other hand take much longer in comparison before alarms go off. In stern drive applications this means melted shutters right away. In applications with resonators, they'll be melted too before you realize there's an overheat. This is why exhaust temp alarm systems are gaining popularity and are on my bucket list.

[bud37]

Okay here is what I was thinking.....is it possible that the impellers in the plastic housings that are above the waterline are sticking to the housing while off and tearing apart on start-up.....one thing about brass, it has an ability to lubricate naturally.

The one I removed had no further damage than the two torn vanes.I guess if the genny in this boat was installed so the pump was easily accessible this would be an easy 10 minute job and that is if you close one eye, lol and this thread would not even be here. Maybe give Sherwood a shout to see if they have a retrofit for this application or see what they have to say engineering wise also. Imo easy maintenance is maintenance that gets done....

[Viper]

Your genny pump is plastic?

[bud37]

Yup, looks like it is made of the same stuff as the merc engine raw water pump spare that i have.

[bud37]

So to add.....I have an email in to Sherwood to see if they have any tech updates and to find out if there is a retro fit brass pump for this Kohler app....we will see I guess....it seems after searching the plastic pump housing is no longer made by them, maybe missing something, but I think I will change to the brass one if it is a straight change with no engineering of the generator shaft.

[mjk1040]

Thanks Viper, will take your words to the wiser and change them this lay up. Mike

[bud37]

So a little to add about the raw water pump saga....seems they stopped making the plastic pump a while back and it it has been replaced with a brass style retrofit, Kohler tech says straight change over.....so I will order one over the big sleep and fit in the spring, and there you have the rest of the story....

[Viper]

Thought that was kind of strange. Don't recall ever coming across a unit with a plastic pump, lucky me!. Kohler must have realized quick that they were problematic and made a change. Thanks for the post, I'll have to keep an eye out for that. I'm sure there are still some plastic units in service.

[CaptBob]

Does anyone have a sure fire way to bleed the antifreeze side of the thing? I know I had problems with it last time, and have forgotten what the trick was. This time I've removed the bleed plug, ran it till it came out solid (no bubbles) reinstalled the plug (ouch! Hot!) but still have a shut down for over heating. Anything I have read is it seems to be hit and miss to make sure you bleed it all out, some fill the plug, some fill the cap, I'm leaning to pulling a vacuum on the bleed plug, the closing it up. There has to be a trick!