oil pressure & closed cooling water capacity 1999 5.7L 350 cid, 260 hp

[rhodesrira]

'New" boat to me so still addressing "opportunities" The engine, a replacement engine, is a 1999 5.7L 350 cid, 260 HP. I've drained and flushed the closed cooling system (I did remove two plugs on the sides of the block) and bought the five gallons of antifreeze supposedly required per the engine tech manual (#24...which states capacity is 20 quarts). Needless to say I only got 3 gallons (12 quarts) in. I presume the tech info is wrong or it doesn't recognize the closed cooling system??? Additionally the oil pressure runs at about 80 psi. The tech manual basically states not less than 30 psi.(I think @1000 rpm) What oil pressure does this engine usually run at operating temp. New gauges are installed Faria and suspect that perhaps the sender is incorrect??? If the sender is for a dual station, could that explain it? Any thoughts ...oh I'm using 20-50 wgt oil. I don't know what was in the engine when I bought it , think it was 30 wgt.as there was a quart left on the baot....but whatever was in the engine it still ran ~80 psi.

Thanks for any insights.