# 20hp merc not circulating water at low iddle when trolling



## Markwh (May 21, 2020)

Hi i have a 2009 20hp 4stroke merc and when trolling at lowest speed it doesn't piss water out but speed up a little or throw in neutral it will and at high speed it does too where do i start- impeller?


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## lemaymiami (Feb 9, 2007)

Your pee hole is just an indicator and may not tell you whether you actually have sufficient water flow... First check to see if it’s partially clogged ( a piece of weed trimmer mono shoved up into that indicator should clear out any debris).

If that doesn’t clear it then you probably need a new water pump. I won’t rig a skiff without a water pressure gauge by the way and it would tell exactly where you stand...


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## Markwh (May 21, 2020)

Thanks ill


lemaymiami said:


> Your pee hole is just an indicator and may not tell you whether you actually have sufficient water flow... First check to see if it’s partially clogged ( a piece of weed trimmer mono shoved up into that indicator should clear out any debris).
> 
> If that doesn’t clear it then you probably need a new water pump. I won’t rig a skiff without a water pressure gauge by the way and it would tell exactly where you stand...


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## Markwh (May 21, 2020)

Markwh said:


> Thanks ill


Thanks will try


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## lemaymiami (Feb 9, 2007)

For anyone with possible cooling/water pressure problems... Talk to your dealer or mechanic about installing a water pressure gauge so that you will know -- one way or the other just what's going on with your water pump... On some smaller engines, installing the water connection may take a bit of ingenuity but it's well worth doing.. Water pressure gauges are mechanical (a water line from your engine powers the gauge). The only wiring needed is for a light on the gauge so you can read it at night... 

When I'm running at night (I do a fair number of night charters each year) the only gauge I ever watch is that water pressure one... If I wrap a plastic bag around my lower unit (or weed) and shut off that cooling water I want to know about it - before my motor overheats...


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## Mako 181 (May 1, 2020)

View attachment 136148
The water pressure gauge is VERY important. I also like my cylinder head temp gauge. But you have to have room for the gauges. I would remove a trim gauge and replace it with a water pressure gauge if I needed the room.

For those with tiller steering and no gauges. I removed the pee tube hose from where the outlet fitting was on the motor and ran some clear aquarium air hose tubing extending it forward to just past where I sit on the bench seat in the jon boat. I then put a brass compression fitting on it thru the hull with a brass cap that I drilled a small hole in to let the water pass. This allowed me to see it peeing while running and without looking back at the motor. I could also place my finger on it and feel the temperature of the water coming out.


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## Brett (Jul 16, 2008)

10 year old outboard, time for a new pump.
Impeller tips are worn, top and bottom no longer seal tightly.
Oring is worn, top of tube seal is cooked, gaskets need replacing.
To be expected and part of normal maintenance.


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