boat water pump problem: update

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waterman

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got a 15 hp 2001 mercury 2 stroke and put a new water pump kit in it. bought complete new housing and all. now when I run it it pees extremely hard then slows way off then pees very hard again. a definite rythym. took it back apart then reassembled and same thing. any ideas on whats up?..................................... after some research, this motor has a thermostat?? just like a car! after pulling it apart twice, checking impeller , seals etc, replaced thermostat and all good. live and learn. only worked on older outboards. had no idea newer outboards had thermostats. urban hunter you were on it! and buccaneer and double brow tine. thanks for the help!
 
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SAWDUST

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Re: boat water pump problem

u positive u got the rubber ears on the pump turned the right way? just a thought.
 
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Urban_Hunter

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Re: boat water pump problem

Thermostat opening and closing possibly?
 
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Buccaneer

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Re: boat water pump problem

What is happening is the motor is running on a bypass circuit until the power head gets to temp and the thermostat(s) open, then as it idles the thermostat(s) may close, putting it into a bypass condition. If this is happening at idle, no worries as power head temps will fluctuate. As long as steady stream is occurring, run it like you stole it.
 
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waterman

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Re: boat water pump problem

as I'm running at full throttle the stream increases and decreases from extremely hard to almost nothing
 
TRIGGER

TRIGGER

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Cunningham TN
Re: boat water pump problem

waterman":26agbjbf said:
as I'm running at full throttle the stream increases and decreases from extremely hard to almost nothing

What’s the time frame on the rhythmic fluctuation?
 
double browtine

double browtine

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Re: boat water pump problem

I would check your water intake screens on the lower unit. Also you could remove the thermostat and spring and run it to see how it acts then. With the thermostat out, it should never let up on flow. If the flow does let up, then you could have a pump issue, or an obstruction inside the engine, possibly a piece of rubber or trash from the old water pump.
 
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Smo

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Re: boat water pump problem

I’ve got a 40 hp Mercury that it takes sometimes 2 to 3 minutes for a full stream to start.

It pees hard when it starts but it just takes awhile too get going.

Kinda like an old man! Don’t ask me how I know these things....
 
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waterman

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Re: boat water pump problem

TRIGGER":3am8dny1 said:
waterman":3am8dny1 said:
as I'm running at full throttle the stream increases and decreases from extremely hard to almost nothing

What’s the time frame on the rhythmic fluctuation?
20 to 30 seconds
 

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