Help. . . impeller replacement question.

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ccdjoe

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My boat has an Onan MDKAU diesel generator that recently started up and shut down along with blinking light that indicated "no sea water being pumped." Boat was in water and exhaust was clearly visible prior to shutdown. After checking filters, etc, I found that I could pour water freely through the intake hose indicating that the sea water intake was not blocked so decide problem has to be impeller. I'm not a great mechanic but have changed a water pump on an old car so I figure that I can do the replacement myself. The part no. is printed on top of the generator so no problem there. I don't have an operators manual so went through a maze of Onan web sites to try to get one or at least a photo/illust on how to replace the impeller. The water pump for the coolant system is perfectly obvious. . . but the location of the sea water impeller is not.
After an exasperating week of searching I have a regional dist. guy supposedly researching what it is that I need to do the job. He said he would call back so that we could complete the order. . . . . . . . He didn't say when. . . . another case of the NC syndrome. . . . subject for a new topic. Can any forum member help? Where do I look to begin?
 
You should be able to follow the hose from the raw water sea strainer that is fitted thru your hull, with a seacock that has a ball valve below the strainer.Follow the hose, the pump would seem to be the logical first pick up point on the generator.

Have you tried this ?

My pump is also belt driven from the engine v belt, so it was mounted on the front of motor.

I had to replace impeller on my Kholer and that is how I found the pump, Just followed the raw water pick up hose, no manual was needed in my case to find it.
 
Give you a hint, when putting impellers in, put a tie-wrap on it draw it up compressing the blades, put it half way in and take the tie-wrap off.
 
I dont remember our exact model number, MDK.... but it is a 17 kW diesel Onan generator about 2005 vintage. After removing the main side sound shield, the impeller is located upper front center and accessed by removing 4x 10 mm (head size) bolts from a plate about 3-4 inches in size. Impeller is easily removed and replaced with the plate removed. As I remember there were hoses going in and out of the seawater pump. Last time I had to dig out a few rubber blades, so I would never wait more than 200 hrs between services in the future. My manuals are on the boat in FL, will be there this weekend if it helps.

-Rick

Viking Sport Cruiser 50 FY
"Silver Lining"
 
Look here to find your pump....http://www.depcopump.com/catalog108/109.pdf............easiest is to take pump off (2 bolts/2 hoses). Simple as eating pie....
 
Good advice y'all. . . my unit has three pulleys, first starting from the drive shaft area to the internal water pump and then to a third pulley with lots of hoses, etc. By taking off the side panel, I followed the raw water intake hose to the third pulley cluster of hoses and shazam there it was. Naturally not easy to open because all four cover bolts faced into the engine necessitating loosing of the entire unit to remove the cover. Old impeller was bound up by two broken blades. Forgot to make a mental note of direction blades were bent when compressed but assume all pulleys rotate clockwise and will replace with that bend. . . ? ? ? ? ?. Also immediately discovered that Jim Pend's trick is a good idea. Thanks y'all.
 
I never paid attention when I replaced my impeller on vane direction. I believe they right themselves when starting up the motor or I just get lucky.
 
Yes, the impeller vanes will flop over to the correct position upon starting. Not an issue.
 
Remember to look upstream if your missing any blades.
 
quote:
Originally posted by rbmitchell

Yes, the impeller vanes will flop over to the correct position upon starting. Not an issue.
Click to expand...


They would have to eventually, but I believe the instructions tell you to install it the right way in the first place.
 
Coat the impellers with Pam, or equalivent, for ease in removing and replacing. Pam will not harm the "rubber".
 
After spending an hour wrestling with vice grips, needle nose and screwdrivers to no avail, called my diesel mechanic and asked the trick for getting the old impeller out. His answer was Dawn dish soap, poured liberally into the impeller housing and then turn the engine over a few times (without letting it actually start up). Impeller slipped right out!
 
quote:
Originally posted by Sandy

An impeller puller can make a PIA job really simple too. The 1st time i used mine I wondered why I waited so long to get one.
http://www.boatfix.com/catalog/593.pdf

Click to expand...
Some of the Sherwood Impellers are threaded, like mine and there is a simple bolt puller

Puller-1.jpg
 
I'm too late but was going to suggest buying a stainless impeller puller. I bought one about 4 years ago for about fifty bucks and its worth its weight in gold. Sometimes they will come right out without one, but now I never have to worry about trying to pry one out.

Second point is to re-assemble the old impeller to ensure that "all" of the impeller is accounted for. If not, you need to chase the missing stuff until you find it.

Third. Here is a bonus trick. Buy two replacements. That way you have a spare.....
http://mvghost.com/voyages/?p=90
 
quote:
Originally posted by giolic

Remember to look upstream if your missing any blades.

Click to expand...


Yours must be much better swimmers than mine as I always look downstream. :D
 
Abalmuth, by threaded do you mean they are threaded onto the pump spindle or pressed onto the spindle and the threads are just for removal?
 
Just looked at the picture of the Sherwood impeller again and answered my own question, haven't seen one like that before.
 
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