Yamaha F15 Pee Hole Problem

[yamahaf15]

I am having a slight problem with the amount of water coming from my pee hole. The amount of water on idle has become weak but I am unable to find the cause. I have replaced the impeller and the internal anodes. When running at higher revs there is no issue but when I go from high revs to idle the flow will stop for 10-20 seconds and then start again but still weak. There still seems to be a good flow at the different weep holes on the lower housing. I have looked inside the engine and it just looks to be a bit of slime inside. Does anyone know why this is happening.

[rodbolt17]

carefully inspect the two tubes on the port side of the head.
if used check the fuel pump cooling lines.
not all had a pump cooler.
when was the last water pump job?

[yamahaf15]

The water pump was only done in August, it does have a water cooler on the fuel pump. What exactly am I looking for? blockage?

Is there some way of cleaning the slime build up from inside the water passages? Its not much but it is visible.

[HydroliftErik]

the easiest way is to check the way of the water from inlet to the "pee-hole".

you might find some corrosion between lower casing and powerhead that blocks the water channels.

[yamahaf15]

But how do you check the passages without ripping everything appart. That seems a little extreem considering I seem to be getting reasonable flow when the revs are up a little

[HydroliftErik]

Its an easy engine to disassemble,
If you don't want to do that, start checking the thermostat, mayby have a look under the cylinderhead.

[yamahaf15]

When I take the cylinder head off will I need to replace gaskets?

Where would you recomend to look first if you were inspecting the water passages?