Rabbitdawghunter
Petty Officer 2nd Class
- Joined
- Jun 20, 2003
- Messages
- 147
I am working on a Mercury 4 cylinder 40 HP on a Tracker aluminum bass boat. It is a 1995 model. I just finished rebuilding the engine and it has been run about 8 hours now so I know the issue is not truly overheat. The overheat horn comes on as soon as the key is turned to the on position. It is a steady horn not beep-beep-beep associated with the oil warning. I found out that the horn stops whenever the temp sender in the block is disconnected and comes back on again as soon as it is reconnected. The serial number on the engine is OG238825. I replaced the temp sender with new when I rebuilt the engine the current part number called for is Mercury #12415. I thought maybe the sender was bad out of the box so this is actually the second sender that is on the engine now. The original temp sender was a very tiny unit that was mounted in the hole beside the #1 spark plug and the new one is much larger and is in a different hole lower on the head. I would think since the horn sounds and goes off as I connect and disconnect the sender that the horn is definitely not part of the problem. I have also replaced the warning module with new Mercury part #14857a16.<br />I don't think the float in the tank would have anything to do with it since the horn goes on and off when disconnecting/reconnecting the temp sender lead. I'm about out of ideas and if anyone knows of any peculiar problems associated with this engine or if there are service bulletins regarding this I would appreciate your help.