Mercruiser Gen 7 Sea Pumps - Possible Suction Issues

When replacing your stock Gen 7 raw water pump with a Hardin Marine stainless pump care must be taken to avoid air leaks. This is the same if you are rebuilding your existing Hardin pump as the same rules apply. An air leak in any of several spots will cause the pump to not prime on initial start up and cause possible damage to the new impeller. Here are some things to double check while upgrading to the Hardin marine Gen 7 sea pump.

  1. While installing the o-ring in the housing that it is greased per the instructions and fully seated in the groove. As a pinched o-ring will cause an air leak and the pump will not prime.
  2. That the gasket between the rear plate and the existing end cap has sealer on both sides and is aligned with the 6 bolt holes. The gasket and wear plate will only fit correctly one way so double check that the 6 bolt holes line up before sealing the gasket in place and tightening the bolt.
  3. Before installing the new or rebuilt Gen 7 pump if your old impeller is missing any blades check the outlet hose. These missing blades could be stuck in the hose, oil coolers, or other places in the cooling system. These broken impeller blades can cause overheating issues. 
  4. Check to make sure the hoses that connect to the sea pump are in good shape and show no signs of wear or cracking. A worn or cracked hose will not seal correctly to the pump and will cause an air leak. It is also a good idea to use a high tack sealer on the hose to barb as this will make for a air tight seal when tightened with the clamp. 
  5. It is a good idea to also check the blue drain fittings as they often crack or have the o-ring no longer seal causing a leak as well. They should be replaced with the Hardin stainless steel drain fitting 625-4289 to be safe. 
  6. Another source for an air leak can be the gasket for the water inlet on the inner transom assembly. The plastic water inlet connection for the hose can also crack and be the source of a air leak into the raw water line. So visually check this connection for any issues.  
  7. While hard to check the water inlet from the out drive and up thru the transom assembly can also be worn or cracked and can be the cause of a air leak or a cooling issue. 
  8. If all of the hoses and water line connections are good and sealed and the Gen 7 pump is assembled per the instructions you will many hours of trouble free use from your Hardin Marine Gen 7 pump.