Not a repower, but wouldn't be surprised if the horn isn't functioning (if present). The hose on the right side in Torcan's pic is from the raw water pump, so I would think the switch/horn would be there to warn of failure in the raw water pumping system. That means to me it would function only with the engine running (grounded the lead with the engine running and got no response -- which might only prove the warning system is past its prime, or maybe disconnected elsewhere).
Anybody have a MerCruiser manual handy that identifies the switch?
unknown sensor
Moderators: BeaconMarineBob, Moderator, BeaconMarineDon
Just an info follow-up. I opened up the t.stat cover, and found a unit in there (from the 90s, based on the stamped info). It was in the closed postion. I expected to find it stuck open, as the engine was running cool. I replaced it with another 140 degree unit, but didn't see any changes to engine cooling. I then replaced the sending unit, with some difficulty in removing the old one without damage -- guessing it was the thirty year old original. The gauge immediately began to respond normally, and the engine registers a little under 150 degrees -- responds to engine speed (lower at high idle, higher at slow idle). I'm guessing there is a little more fluctuation related to speed of raw water pump than in a closed cooling system like I had in an earlier boat. I haven't taken the boat out and run it yet to test, and hope the temp stays in the 140 -150 range or so at operating speed.
The engine is warmer to the touch at the manifold and risers, so I'm thinking the t.stat was lazy in closing. Curiously, though, the t.stat cover doesn't seem to get into the 140 degree range (by touch test). I did a partial test on the old t.stat by immersing it in about 200 degree water to see if it opened -- which it immediately did. It may have been slow to close up when removed from the heat, but not really sure. I figure that the temperature issue should be resolved with the new t.stat and sender, and will just try to run it with the fixes.
"unknown sensor" remains disconnected, so I don't know if the warning horn is working. I might replace the warning switch/sensor, although I'm not sure yet it's worth the $68 for the switch.
Thanks for the input -- wish this stuff had been handled as routine maintenance by the prior owner, but think I'm getting things caught up.
The engine is warmer to the touch at the manifold and risers, so I'm thinking the t.stat was lazy in closing. Curiously, though, the t.stat cover doesn't seem to get into the 140 degree range (by touch test). I did a partial test on the old t.stat by immersing it in about 200 degree water to see if it opened -- which it immediately did. It may have been slow to close up when removed from the heat, but not really sure. I figure that the temperature issue should be resolved with the new t.stat and sender, and will just try to run it with the fixes.
"unknown sensor" remains disconnected, so I don't know if the warning horn is working. I might replace the warning switch/sensor, although I'm not sure yet it's worth the $68 for the switch.
Thanks for the input -- wish this stuff had been handled as routine maintenance by the prior owner, but think I'm getting things caught up.
Motors should run. People -- not so much.
1980 F26, Mercruiser 305
1979 14' Starcraft, 1957 18 hp Evinrude and '57 3hp Evinrude kicker
1980 F26, Mercruiser 305
1979 14' Starcraft, 1957 18 hp Evinrude and '57 3hp Evinrude kicker