water pumps and impellers

[john-eh]

Alright I heard that there are 2 types of water pumps and impellers used in outboard motors? If so, what are the 2 types, and are there any differences??

 

[Silvertip]

Re: water pumps and impellers

If there are two types they must be different in some respect. However, every current outboard has a single rubber impeller built into the lower unit of the motor. Its driven by the drive shaft. When the engine runs, it runs. While size and type varies from manufacturer to manufacturer and by engine HP, they all operate basically the same. If you consider that to be different, then there are a couple hundred types. I/Os on the other hand have two pumps. One like I just described in the lower unit, and one on the engine. Again, they operate in similar fashion but a water pump is a water pump.

 

[john-eh]

Re: water pumps and impellers

alright thanks for that! So you are saying that impellers are any different except for the shapes and sizes, but the only difference in water pumps is that it can be located on the engine or the lower unit?

 

[TOHATSU GURU]

Re: water pumps and impellers

Outboards have one waterpump located in the lower unit. Inboard/Outboards have two. One in the lowerunit and one on the engine.

 

[Dunaruna]

Re: water pumps and impellers

Ecept for VP, no lower unit pump.

 

[saumon]

Re: water pumps and impellers

I've heard (at least on Merc. 40-60hp from the '90s) that some models had high volume w/p and others have high pressure w/p???<br /><br />Not sure of the difference...

 

[Silvertip]

Re: water pumps and impellers

Pouring water out of a bucket is "high volume". Getting hit with a stream of water from a fire hose is "High Pressure". Voume = gallons per minute. Pressure = PSI or pounds per square inch. Your home water system (city water) is probably in the range of 60 - 80 PSI. At that "pressure" and considering the pipe sizes, it will deliver "xx" gallons of water per minute. A big pipe at low pressure can deliver as much fluid as a smaller diameter pipe at higher pressure. Pretty basic physics.

 

[saumon]

Re: water pumps and impellers

Thanks a lot Upinsmoke, it's very kind of you to explain this! When i say i wasn't sure about the difference, i doesn't mean between pressure and volume, i meant how does it's applicable to waterpump...<br /><br />Maybe the high pressure type had smaller passageways and water is pushed to the powerhead with more pressure? Don't know...

 

[danie]

Re: water pumps and impellers

Hang on. Maybe john-eh is referring to different types of material. Like a rubber impeller vs a silicone/nylon/whatever impeller.

 

[Silvertip]

Re: water pumps and impellers

But that doesn't make it a high pressure pump. It merely means the system pressure is higher because of reduced cooling system size. In that example both impellers would have the same part number. I'm not aware of any outboard that does not use a rubber impeller style water pump so in my view, there is no difference. If you happen across the part numbers for these "high pressure" pumps let us know.