I have a 1988 mercuriser 5.7 (carb) Alpha 1 equipeed boat and it
recently started running a little hot - not overheating but hotter than
normal. It normally runs at an indicated 130 degrees or so under any
conditions - idle, cruise, wide open, summer and winter. The other day
it started climbing up to 180-ish at low rpm's and went down to 150-ish
at cruise (3000 rpm). It ran at a steady temp for a while and then I
decided to try wide-open. The temperature started climbing pretty
quickly so I brought it back down. The temp came back down to less than
160 and stayed. This happened all of the sudden with no known causes.
The pump in the outdrive was replace in May (annual maintenence), the
recirculatiing pump on the front of the engine was replaced 2 years
ago. The manifolds have not been replaced since I bought the boat in
November of 2001. I'm in salt water (Chesapeake Bay) BTW. Oh I
forgot, I took out the thermostat and it seems to be working properly.
Both it and the temperature sender were replaced at the same time as the
circulating pump. So, what's up? Is it a clinker?