200 optimax fun fun

[andrewddrennon]

Working on a 200 optimax. starting serial number 0g38 . New w/p and poppet valve. Anyway you run the boat say 1/4 mile trimmed out 5200 rpm and you will get a horn for maybe 1 second....then stop. Mercury cds shows no actual overheat counters. But low block water psi will cause a horn through the temperture switch. It is the first generation of optimax and they dont store much in the way of historic faults. It wont do it trimmed all the way in and the problem has arisen recently. Anyone had a scenario like this before? Need some good ideas.