i have a 1988 carver santego with twin 4.3 vortecs new in 1996. last season for whatever reason the starboard motor, after about 3 minutes of cruise at @3500 rpm, the temp gauge would drop , not rise, from a normal 175 to almost nothing. after bringing it back to idle it would slowly rise back to normal, never overheating. i brought it to my boat mechanic for regular maintenance and told him about the problem. i replaced the outdrive waterpump, water circulator pump, risers and manifolds with riser gaskets with the cut outs on four sides, spark plugs and thermostats. also cleaned out all the fish eggs and other crap in the outdrive cavity. we started it up with the hoses disconnected at the bottom of the manifolds and saw it was getting plenty of water. took it for a ride and did an infared test and it was running normally. it was fine for the season. now its a new season and i'm having the same problem. i had replaced all the gauges with new ones, and replaced the tempurature sending units. i had water in the oil last year due to a waterheater hose spliting on top of the intake manifold and water getting sucked into the carb. we fixed that intime with no damage to the motor, oil has been water free. a pressure test on the motor was done and uneventful. i was told my gauges are off about plus ten degrees also, mabey a bad ground? any ideas?
