ok i have a 96 502 mag with a harden marine stainless sea water pump with a new impeller. i put a autometer water pressure gauge on coming off the thermostat housing. i have 0 psi idling. when i throttle up to get on plane i have about 6 psi. when i get on plane and throttle back to 3000 rpm i have about 3 psi pressure. this seems awlful low to me when i see guys putting water dumps on to lower the pressure. it does not overheat but i would feel better with a little more pressure say 10 to 15 psi. any suggestions? thanks

Pressure is no indicative of flow. Pressure is resistance to flow. Dunno what the right number should be but as long as there is enough volume to keep the temps right..... it's fine

thats true. i read where other guys are bleeding pressure off. i certainly dont have that problem.

Same numbers I have on a plain 'ol 7.4 mpi.

5-10 is plenty. Any more than that and its putting unwanted pressure on seals and gaskets

mine runs about 12-13at idle and around 25-30 at higher rpm's

Do you have a temp guage, what is it reading

that is close to waht it should be ...a little on the high side here.

But u need min pressure to get airpockets out flow also needs to be there but pressure is just as importent !

temp gauge reads fine. 160 170. it just seems like if it was feeding the motor enough water there would always be some pressure. dont like ever seeing the gauge sitting on 0 at idle. should at least be some pressure . i am thinking about switching back to a merc plastic pump to see what happens . other guy has same readings as me , and you seem to have high readings.

Well the temp seems fine are you sure the guage is good, hell mine could be way off now that i mention it be my temp is good. Do you have plenty of water coming out off exhaust