Have a 2008 Yamaha 20hp four stroke on a jon boat that I use on the river. Put it in to go put out some catfish baskets, and I noticed it wasn't "peeing" as it should. Got a water pump impeller, replaced it, still no pee.

So here's what I've done:

1. Checked the intake screen on the foot for a blockage. Good there.
2. Fed water from the water pump housing to check to make sure the intake wasn't blocked before the water pump. Good there.
3. Run a wire through the "pee" hole. Couldn't get much there because there's a bend in it.
4. Run a wire up the pipe that goes from the water pump housing, up the foot, toward the base of the engine. At the top of it there is what feel like a spring loaded baffle of some kind. Was able to move it up and down fairly easily.

Some other observations that I've made:

1. When the engine runs on the flusher, there are puffs of air coming out of the "pee" hole, but no water.
2. If I force water into the "pee" hole, water runs back out of it for several seconds but finally ends.
3. If I force water up with the foot of the motor off, nothing comes out the "pee" hole.
4. I have a hose attached to the motor that will allow you to feed water into the engine without it having to be drawn up through the water pump. If I do that the water lines feeding the engine are getting water, but no "pee."

So I'm at a loss folks. Sense collectively you all know pretty much everything, any help on finding the problem would be appreciated.

I am guessing that you still have water coming out of the exhaust. My guess is that you have a hole corroded from the water jacket to the exhaust manifold side of the engine

Is it actually overheating, or is it running normally?

I haven’t ran it long enough to see if it would overheat.

Did you replace the impeller properly

Sanfo008,

Check the rubber tubing that connect the tube coming up from the lower unit to the tube that connect to the motor. You will have to pull the 2/3 bolts that hold the lower unit to the upper part of the motor shaft, and may have to disconnect the shift rod clamp. There's a short robber hose piece the connect the tubes together. Check if it's connected, as if you replaced the water pump, it's easy to either forget to replace it, or it slipped off.

Keep the shifter in neutral and make sure that the lower unit is in neutral also...prop will spin both ways by twirling the prop with your finger.

Hope this helps!

Run a wire into the tube that runs to the pee hole as far back as you can. It doesn't take much to plug that tube up. You may need to replace that water tube which is very simple to do

It is only an indicator.( the pee hole) Is water coming out the exhaust ports that’s the cooling water. I say the tubing is blocked. open it or replace it first. If no water coming out the exhaust then the impoeller could be faulty.

Small spiders will pack in bugs and debris and plug those pee holes and can be hard to get them cleaned out.

Last year I had a similar problem. I run in saltwater, and don't always flush with fresh. I had tiny salt build-up in the pee tube. Compressed air fixed the problem.

check if it has a thermostat. I had a 40hp that i thought had a bad water pump it ended up the thermostat was not letting enough water to get through.

If you've exhausted all the other suggestions then this is very likely the problem.

Checked the thermostat this morning. It was clean and functioning properly. Decided to start disconnecting hoses and clearing out fittings and connectors and whatever else I could find. Finally found the clog of mud in a 90 degree bend in a brass fitting. Of course it was the last one I checked!

This was certainly an educational experience. I thought it was going to whip me.

Thanks for the feedback everyone.

So, would the compressed air trick have cleaned it out?