Yanmar 3YM30 fails to self prime

Jun 14, 2010
2,081
Robertson & Caine 2017 Leopard 40 CT
Has anyone else ever experienced this? Even after filling the raw water strainer it still had a problem priming. I’m assuming the raw water pump s just too worn, or impeller needs change out. Surveyor says all raw water pumps aren’t self priming. All in my experience are, until this. Have I just been lucky? Or dumb?
 
Oct 22, 2014
20,995
CAL 35 Cruiser #21 moored EVERETT WA
I have not had a problem with my Perkins.

Is the location of the strainer raised to high above the waterline and the pump?

Is there an issue with the impeller?
 
Oct 29, 2005
2,355
Hunter Marine 326 303 Singapore
Try turning the cover around. Sometime the cover (facing inside) is so wore that results in leaks between the vanes causing airlock/not pumping.

Ken Y
 
May 17, 2004
5,032
Beneteau Oceanis 37 Havre de Grace
I did have the problem once but filling the raw water strainer (by closing the seacock, pouring in water, closing the top, then opening the seacock) fixed it. Could be the impeller like you said but also be sure the strainer is fully sealed.
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
Check the strainer. Some of the old Perko and Groco strainers used cork gaskets between the glass bowl and the bronze pieces. Over time the cork deteriorates and no longer holds a vacuum. Air leaks in and breaks the prime.

Cheap fix, get some cork casketing at an auto parts store and cut new gaskets.
 
Jan 4, 2006
6,444
Hunter 310 West Vancouver, B.C.
All in my experience are, until this. Have I just been lucky?
Never given mine a second thought whether after doing a pump inspection, playing with the hoses or sitting on the hard for a few day. I've got a flow switch and it cancels the extremely annoying audible alarm the second the engine turns over.
 
Mar 3, 2003
710
Hunter 356 Grand Rivers
You might have an air leak - at the strainer, ,maybe at the pump gasket, or your impeller may be bad. All three can cause you not to flow. Also if the I,pellet is bad and has pieces missing, check the hoses up to and including the heat exchanger and remove amy blockages from the impeller.
 
Jul 8, 2005
512
Jeanneau 389 Grosse Pointe Farms, MI
Has anyone else ever experienced this? Even after filling the raw water strainer it still had a problem priming. I’m assuming the raw water pump s just too worn, or impeller needs change out. Surveyor says all raw water pumps aren’t self priming. All in my experience are, until this. Have I just been lucky? Or dumb?
Did you remember to open the fresh water valve?

I had this issue once years ago and it was the gasket on the fresh water strainer. Check it to be sure it is not broken. You can even put a small film of plumbers silicone grease on the gasket if it is dry.

I will be changing the impeller on our 3ym30 in a few weeks....
 
Mar 29, 2017
576
Hunter 30t 9805 littlecreek
Definitely sucking air. Will cause overheating you can close valve and shove water into pickup tube and look for leak
 
Jul 8, 2005
512
Jeanneau 389 Grosse Pointe Farms, MI
Has anyone else ever experienced this? Even after filling the raw water strainer it still had a problem priming. I’m assuming the raw water pump s just too worn, or impeller needs change out. Surveyor says all raw water pumps aren’t self priming. All in my experience are, until this. Have I just been lucky? Or dumb?
Check and make sure the belt that drives the water pump is correctly on the pulley. Years ago, I didn't put the drive belt in the right place and it didn't work well....