Researched here and found that the Sender for sea water pressure in a 525 is suppose to be in the water exchanger on the front of the motor, starboard side.
I find no such thing. Any ideas where else to look. The parts breakdown diagram also shows it to be on the exchanger.

oil cooler

here made it easy for you check out oil cooler and part # 42 in the parts diagram

http://www.boats.net/parts/search/Me...%29/parts.html

As Bup said, it's in the oil cooler on the rear of the engine. It's on the starboard side, near the end of the cooler, right in 5he top.
Eddie