Water Pressure

[mibowman]

Greetings,

Have a yamaha 150 pro V . The water pressure was always between 20 and 23 running at 5000 rpm. Recently I have noticed the pressure moved to 25 at 5000 rpm. Yesterday the pressure was between 28 to 30 at 5000 rpm.

Could this be an issue relating to the impeller?

As always, Many thanks to all who help on this site.

Brian

 

[Turbojoe78]

Re: Water Pressure

Just a guess but, I would think that if the pressure was going up than your impeller is working good and you're getting some kind if restriction between the impeller and after where the pressure readings are taken from.

 

[mibowman]

Re: Water Pressure

Thank you for the reply. Can you expand on this reply please?

 

[Turbojoe78]

Re: Water Pressure

I know very little about the cooling water flow route of an outboard, (just got mine about a month ago) other than it enters through the lower unit, gets pumped through the cooling jackets of the engine by the water pump and is controlled by thermostats to keep the engine at a desired temp, then gets mixed with the exhaust and exits the drive through the prop.

I am however very interested in the system because the boat I have has a quicksilver water pressure gauge that looked to be plumbed to the motor (previous motor) by a plastic water line coming from the motor area.

My thought would be, that you would tie the pressure sending line in between the water pump and the thermostats, so that if the thermostats started to fail to open all the way you would notice a rise in water pressure after the motor was warmed up. (as you have noticed on yours)

As I started with ... I know very little about this stuff ... my GUESS would be your thermostats are not opening all the way, or you are getting a build up of something in the cooling jackets making your pressure go up.

With that I will step back and let someone with much more knowledge than I help you with a good place to start your troubleshooting.

Joe

 

[99yam40]

Re: Water Pressure

could have a PRV (Pressure Relief Valve)
Sticking and not relieving the pressure under high RPM