70 water pump issue

[<jkent>]

I have a 1987 70 horse. I installed a new water pump. I mean everything including the alum. lower housing. At around 2000 rpm I have about 16 psi. At idle the psi quickly fades to 0. Get back on the gas and psi returns. The thermostat was removed a long time ago. This motor has no presure relief valve that I can tell. Can anyone please give me some advice?

[<boats.net>]

The 70HP is a low pressure high volume cooling system and if you are getting any pressure at all you are doing good.

[<jkent>]

At idle the pressure is Zero. I believe I have a bad seal at the top of the water tube.

[<jkent>]

What I mean by zero pressure at idle is that water stops coming out the tell-tale and the motor quickly over heats. If I increase the RPM's the water returns and quickly cools off.