mobocracy
Active Member
I've been reading up on the process for impeller changes on Mercruiser engines. I am not an engineer or experienced with these things but it seems like a really dumb design.
If they're going to use a fast-wearing material for the impeller, why make replacing it involve so much disassembly? It looks to me like from posts here, youtube videos, etc, replacing it in the boat involves pulling out the entire pump assembly. Couldn't there have been a design with an easily accessible pump housing cover?
Better yet, why make the impeller out of rubber at all? Why not make it out of metal? Of course this might imply a more complex straining system if part of the purpose of the rubber impeller is to provide give if junk is ingested into the intake.
Which itself systems to be a system design problem -- how about some kind of intake filtering that prevents ingesting sand or other debris? I'd rather check and clean a sea strainer once a week than tear out the pump to replace the impeller, even if the filtering was necessarily limited to maintain water flow volume I'd rather replace an entire all-metal pump every 5-7 years vs. hours of labor ever 1-2 for a self-destroying impellers.
There seem to be other problems besides the impeller, the OEM pump impeller wears against the housing. It looks like a company called Hardin marine makes a replacement pump that fixes this, using replaceable wear plates that keep the impeller from destroying the housing. I just recently bought a 2007 310DA with 350 Mags and was having the impellers replaced as PM and of course got the call that one of the pump housings fell apart as it was being removed and needed to be replaced.
The Hardin pump actually looks like a significant upgrade over the factory pump. I have bookmarked that site so that I might even proactively replace both sea water pumps when its time to service the impellers.
OK, I'm sure I don't know what I'm talking about here and there are reasons for these designs that go beyond "it was the simplest way to make a GM block into a marine engine" and "mercury market dominance means we don't have to try harder".
If they're going to use a fast-wearing material for the impeller, why make replacing it involve so much disassembly? It looks to me like from posts here, youtube videos, etc, replacing it in the boat involves pulling out the entire pump assembly. Couldn't there have been a design with an easily accessible pump housing cover?
Better yet, why make the impeller out of rubber at all? Why not make it out of metal? Of course this might imply a more complex straining system if part of the purpose of the rubber impeller is to provide give if junk is ingested into the intake.
Which itself systems to be a system design problem -- how about some kind of intake filtering that prevents ingesting sand or other debris? I'd rather check and clean a sea strainer once a week than tear out the pump to replace the impeller, even if the filtering was necessarily limited to maintain water flow volume I'd rather replace an entire all-metal pump every 5-7 years vs. hours of labor ever 1-2 for a self-destroying impellers.
There seem to be other problems besides the impeller, the OEM pump impeller wears against the housing. It looks like a company called Hardin marine makes a replacement pump that fixes this, using replaceable wear plates that keep the impeller from destroying the housing. I just recently bought a 2007 310DA with 350 Mags and was having the impellers replaced as PM and of course got the call that one of the pump housings fell apart as it was being removed and needed to be replaced.
The Hardin pump actually looks like a significant upgrade over the factory pump. I have bookmarked that site so that I might even proactively replace both sea water pumps when its time to service the impellers.
OK, I'm sure I don't know what I'm talking about here and there are reasons for these designs that go beyond "it was the simplest way to make a GM block into a marine engine" and "mercury market dominance means we don't have to try harder".