Installing a new impellor on a Universal 12 engine......it's a Sherwood pump. Well, you guessed it, I removed the old impellor last fall and I've forgoten which direction the thing rotates which seems important as I scrunch the new one back in there. And yes, you guessed it again, that was stupid. But....with any luck, maybe it's the last stupid thing I'll do. Anyway, looking at the old impellor, I can't really be sure. Guessing from the design of the inlet/exit holes inside the pump itself, I'm thinking a clockwise rotation, but I'm only guessing. Anyone just go through this? Thanks. Brad
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Hit Starter Switch Momentarily
If you would still like to know, just hit the starter switch momentarily and see which way the crankshaft pully and all the belts turns. While I agree that what Bob said will probably work, for what it's worth, my Yanmar manual says to put the vanes in the proper direction. Suggest putting drawing an arrow (felt tip marker or ?) on the crankshaft pully to indicate the rotation direction for future use.
If you would still like to know, just hit the starter switch momentarily and see which way the crankshaft pully and all the belts turns. While I agree that what Bob said will probably work, for what it's worth, my Yanmar manual says to put the vanes in the proper direction. Suggest putting drawing an arrow (felt tip marker or ?) on the crankshaft pully to indicate the rotation direction for future use.
Thanks Bob and John
I appreciate the insight. And, the idea about drawing an arrow for the future is great. Thanks. Brad
I appreciate the insight. And, the idea about drawing an arrow for the future is great. Thanks. Brad
Right direction is important
cuz you have to bend the vanes to get the impeller into the housing, and if you guess wrong, the vanes will break when the pump tries to rotate 'em the other way.
cuz you have to bend the vanes to get the impeller into the housing, and if you guess wrong, the vanes will break when the pump tries to rotate 'em the other way.
Grease it up
I always put a good coating of white grease on the impellor and inside so the thing can slide into position without binding the first time the engine cranks. Remember, it will be dry the first time the engine starts.
I always put a good coating of white grease on the impellor and inside so the thing can slide into position without binding the first time the engine cranks. Remember, it will be dry the first time the engine starts.
Key Problems ... I was given a carbon steel key
the last time I changed the impellor and it didn't last 9 months ... what is the key? supposed to be made of? Vic
the last time I changed the impellor and it didn't last 9 months ... what is the key? supposed to be made of? Vic
Lube it up
After a few thousand impeller changes over the years, most impellers go on either way. Unless they have a key way they are a universal fit either way you put them on. There is no "right" or "wrong" direction for an impeller to be installed. As previously advised, you need to lube them up with some kind of high quality grease -- I use silcone grease available from most dive shops -- and generously glob it on the impeller and inside the impeller cavity for those brief moments when no lubrication, i.e., water is being pulled through it. If you don't lube it up, it will suffer a little heat damage until the water hits it and it could fail with a tab breaking off and possibly blocking the water line after being ingested into the cooling system.
After a few thousand impeller changes over the years, most impellers go on either way. Unless they have a key way they are a universal fit either way you put them on. There is no "right" or "wrong" direction for an impeller to be installed. As previously advised, you need to lube them up with some kind of high quality grease -- I use silcone grease available from most dive shops -- and generously glob it on the impeller and inside the impeller cavity for those brief moments when no lubrication, i.e., water is being pulled through it. If you don't lube it up, it will suffer a little heat damage until the water hits it and it could fail with a tab breaking off and possibly blocking the water line after being ingested into the cooling system.
Impellor basics
Some impellors have straight vanes, in which case it doesn't matter how the impellor is installed. Water is sort of "thrown-out" from center of rotation. Others have curved vanes. For those types, determine the outlet pipe direction. The curve vanes usually curve (as in to scoop water) toward the direction of the outlet pipe. Did I add to the confusion?
Some impellors have straight vanes, in which case it doesn't matter how the impellor is installed. Water is sort of "thrown-out" from center of rotation. Others have curved vanes. For those types, determine the outlet pipe direction. The curve vanes usually curve (as in to scoop water) toward the direction of the outlet pipe. Did I add to the confusion?
Not quite, Doug
ALL impeller vanes are straight when they come out of the package...they only become bent from use. An impeller has to be a very tight fit----such a tight fit that it's necessary to rotate it enough to bend the vanes to get it to go into the housing--in order for it to be able to impel (move) anything through the pump. If water were just "thrown out from the center of rotation" like a lawn sprinkler, there'd be no pumping action...that requires a combination of centrifugal force and a tight seal to create a vortex that impels (pump) liquid through the pump...without it, the pump can't prime. It's why impeller pumps fail if they're run dry--when friction heat wears off the edges of the vanes, there's no longer any seal to create the vortex. That's why it's important to know which way to bend the vanes when you install a new impeller...if you bend 'em one direction and the pump turns the other direction, neoprene isn't flexible enough to adjust and flip over in the right direction...the vanes crack. When that happens, if you're lucky all it'll cost you is another impeller. But if the pump manages to "swallow" a piece or two of neoprene before it quits, the pieces have to be retrieved--sometimes from places that are impossible TO retrieve 'em--or they can cause serious problems elsewhere in the system.
ALL impeller vanes are straight when they come out of the package...they only become bent from use. An impeller has to be a very tight fit----such a tight fit that it's necessary to rotate it enough to bend the vanes to get it to go into the housing--in order for it to be able to impel (move) anything through the pump. If water were just "thrown out from the center of rotation" like a lawn sprinkler, there'd be no pumping action...that requires a combination of centrifugal force and a tight seal to create a vortex that impels (pump) liquid through the pump...without it, the pump can't prime. It's why impeller pumps fail if they're run dry--when friction heat wears off the edges of the vanes, there's no longer any seal to create the vortex. That's why it's important to know which way to bend the vanes when you install a new impeller...if you bend 'em one direction and the pump turns the other direction, neoprene isn't flexible enough to adjust and flip over in the right direction...the vanes crack. When that happens, if you're lucky all it'll cost you is another impeller. But if the pump manages to "swallow" a piece or two of neoprene before it quits, the pieces have to be retrieved--sometimes from places that are impossible TO retrieve 'em--or they can cause serious problems elsewhere in the system.
wire ties
I forget where I read this, but here's what I have done. Before you take the old impeller out, make a note which way the vanes are bent. Then take the new one and wrap a plastic wire tie around it to put the vanes in the correct bend direction. Now put the new impeller in the hub and as it's going in, take off the wire tie. Now it's installed with the vanes pointed in the correct direction. rp.
I forget where I read this, but here's what I have done. Before you take the old impeller out, make a note which way the vanes are bent. Then take the new one and wrap a plastic wire tie around it to put the vanes in the correct bend direction. Now put the new impeller in the hub and as it's going in, take off the wire tie. Now it's installed with the vanes pointed in the correct direction. rp.
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