How can I

[TONYPOGO]

Hi, my outboard start overheat after 5-10 min even on idle speed. And this is not a thermosensor foll because stem comes from nipple.I change water pump impeller, thermostat, NIPPLE has good stream of water.Wen I take the thermostat out a lot of water cam from hole on idle speed. what else I have to try?

[99yam40]

possibly have plugged cooling passages.
may need to that apart and clean them.

It normally helps to state what motor you are dealing with when asking questions

[TONYPOGO]

how to check water pressure in cooling system?

[boscoe99]

One way is to get a pressure gauge from Home Depot. Install it on the end of the garden hose flush fitting. Run the motor at speed and observe the reading on the pressure gauge.

[TONYPOGO]

sorry , my motor is 2002 F40MJHA Yamaha Jet Drive

[TONYPOGO]

I check already by home depot gauge and only 2-4 psi and not comes more pressure on medle idle

[TONYPOGO]

what is port to be apart and clean first in your opinion?

[TONYPOGO]

I meen part

[99yam40]

idle is not at speed

head and cover along with exhaust plate

[TONYPOGO]

you meen CYLINDER HEAD ASSY
67C-W009A-00-1S and 67C-41113-01-1S OUTER COVER, EXHAUST?

[TONYPOGO]

do you have diagram of the cooling system on F40 HP 2002?