Minimum water pressure?

[VMS]

Hi everyone..

What is the minimum water pressure for a 2005 90hp 2 stroke? I'm in the process of raising the motor up for better performance and do not want to fry up my motor by going too low on pressure. I have a service manual, but I cannot seem to locate a minimum water pressure.

Thanks!!

Steve

[Ken]

Steve,
Your water pressure will vary from about 8 pounds at idle to about 20 WOT - assuming the intake to the pump is not sucking air.
If your water pump starts starving for water, then the pressure is going to fall - if the incoming water is cold enough, then you won't need a lot of volume - but in the summer when the water temp is high, then as soon as the water pump starts sucking air and the pressure drops, then you are probably going to overheat pretty quickly.
You say you are going to raise your motor for better performance - you want the cavitation plate of the outboard riding just on top of the water surface when you are trimmed out for max speed and no ventilation. You don't want it down in the water, just on top. You raise it anymore, then your water pump is going to start sucking air, and overheating will soon follow.
There is a thermoswitch mounted in the head of your 90 hp Yamaha - it will close at around 180 degrees f. to indicate an overheat condition - the alarm will sound, and a few seconds later, the motor will go into rpm reduction mode so that you will throttle back to neutral and fix the problem. At this point you have not done any damage.
Hope this helps [img]smile.gif[/img] ,
Ken K

[wellsc1]

2003 too?

Ken,

I just joined this forum and found what I was looking for, I think. Are the presure stats for 2003 90hp Yamaha 2-cycle, 3-cylinder. The same as you specified for 2005? If not, please specify for 2003 model. Carl W

[boats.net]

Yes they are.