Sierra water pump impellar woes 15hp

[cool6string]

Any one out there had trouble getting omc water pumps to work effectively using the aftermarket water pump impellars by Sierra? I had a pump on my 15 Johnson that would not self prime. After no success (water dribbled out **** tube at mid speeds & not at all at idle. Re-ran engin with out lower unit with garden hose to water uplift tube & all passages are OK, pisses great & runs cool. Testing lower unit in a barrel running drive shaft by drill revealed pump would not self prime at all. Pump would sluggishly work when completely submerged (the pump itself). Dissassembled & compared old (omc)impellar to Sierra. Sierra was shorter by .020-.030". Resulted in a gap between impellar plate by .040. It seems the efficiency went to hell because the impellar is too short. Note: on this model they don't use a base gasket under impellar plate & have to rely on OMC "M" adhesive there. I'll test the motor Friday. I sanded the base of the impellar housing to achieve almost net height of the impellar. I still have about .000-.005 clearance in height (impellar to impellar cup cavity). I've done MANY outboard pumps before. Never saw one that wouldn't work. Should I have made a friction type fit in terms of height? I expect this one to **** like a racehorse now! The efficiency has to be much better. Any thoughts out there.

 

[Solittle]

Re: Sierra water pump impellar woes 15hp

cool6string - Even an OMC pump needs to be submerged to pump properly. I'm curious why you did not get the OMC pump & avoid the hastle???

 

[Hooty]

Re: Sierra water pump impellar woes 15hp

When replacing the waterpump, you're a lot better off if you replace the whole thing, housing and all, not just the impeller.<br /><br />c/6<br />Hooty

 

[cool6string]

Re: Sierra water pump impellar woes 15hp

SoLittle, My local OMC dealers were out of stock so tried a complete Sierra kit first & bought an extra impellar to use with my old omc housing on another motor (it was still like new). I went in to this motor to reseal the upper gear case seals initially & change the pump. Also I found a complete new OMC water pump kit hanging on the peg board last night. (I've got several 9.9 & 15's)I am normally a diehard OMC parts guy. Thought I'd try the aftermarket crap. Has any one seen a drop in efficiency on pump performance with these aftermarkets kits?<br /><br />Hooty, As mentioned above whole pump kit was my first attempt. The OMC pump housing was mine. I didn't want to sand the Sierra housing as I might still return the sierra kit. Besides the OMC housing gave the best fit. I'll test my alteration Friday. I'll let you know if it made a difference. P.S> all the fuss is to make my motors easy to sell. No one would buy it with poor water pump performance...

 

[Hooty]

Re: Sierra water pump impellar woes 15hp

Please do let us know. Like you, I use oem parts when available but I've used Sierra parts before and never had a problem. <br /><br />c/6<br />Hooty