Water output per hour?

[Thompsoncustom]

I was wondering if anyone knew how much water a 64 johnson 6hp could pump an hour or minute. Or maybe a good way of testing it? Thinking about changing where the water is picked up on the motor using some welding, hoses, and a pump. The pump could pick up water right off the bottom or back of the boat to try in eliminate sucking so much sand in the really shallow river here. Just want to make sure the I don't use a pump that can't keep up with the impeller.

 

[oldboat1]

geez. You're not well, thompson. That's a good engineering question, and I'll bet somebody here knows specifically how much per minute, and will provide a citation.

great historical question too -- gave us those mudflats motors and air cooled outboards, presumably. Some air cooled motors also had an impeller that I think was used to cool the leg/exhaust housing -- idea (yours) would be to use a fabricated water cooled system instead of air cooling the powerhead.

I'm guessing a gallon a minute for a 6 hp (trying to picture how much would be pumped up through the water tube if left open). And maybe that's way off. I would think simplistically of cutting/disconnecting the water tube between the impeller and the powerhead, and installing an inlet in the water jacket or maybe in the exhaust housing cover on the powerhead, or both -- then running tubing from a pump mounted on the stern of the boat to the inlet. Let the plumbing otherwise stay in place for exhausting the water. Maybe the existing impeller could be used to cool the exhaust housing, but would have to be more hardy than the rubber ones or the sand would eat it up.

??

 

[Tim Frank]

Easier to just get an air cooled O/B.
This is a recipe for disaster....at least IMO.

 

[oldboat1]

Indeed. but a fortune to be made. Tough part now is to power the stern pump by the outboard -- maybe a generator system. Maybe just a battery powered pump with a high output alternator charging system on the motor. (don't see a charge rate keeping up offhand, with a high output pump -- but just another engineering question....)

 

[Scott Danforth]

while I have never looked at small impeller curves, guessing by size and RPM, about 3-4 GPM.

you will not be able to use the alternator on the motor to power an electric pump. just not enough current there to feed a motor to provide the proper amount of flow (every conversion from mechanical power to electrical power to mechanical power will simply loose efficiency)

I personnaly would make an air-cooled long-tail mud motor if you have that much problem sucking sand and mud because your lower is burried in it or get an air-cooled outboard.

 

[Thompsoncustom]

Thanks for the input guys, ya there are a couple around here with gator tails and jet jon boats but I figured I have this 6hp and it shouldn't be that hard to change the pickup location. There are quite a few 12volt pump that can put out 5gpm that I could just run off my battery but it might not even require a different pump. Seems like all I would have to do is remove the screen and plug and replace them with a solid plug than build a new inspection door or whatever it's called that was 100% sealed the gear case when tightened down. Now as long I put a 1/2 nipple on the new inspection door that should be the only place it can pull water through and all I would have to do is run the hose where I wanted.

Doesn't seem that hard but only one way to really find out.