Re: 50 hp mercury overheating horn
welcome to iboats, roots.<br />A mechanic will have to service your motor, or he will be replacing one instead.<br />The impeller must be changed-out, if it has not been changed-out in the past 2 seasons, or has sat for longer than a year without being turned over. This is to be considered 'normal' maintainance item.<br /><br />My best guess --the impeller is your problem ,because the water hose (under pressure), forces itself thru the cooling circuit, while the impeller must creat it's own pressure for that.<br />Any time the alarm sounds, the motor has overheated, and damage has occured. So do not run it with the alarm sounding..shut it down imediately,and after the problem has been fixed, have the compression tested. They melt-down quickly from overheating or lack of oil in the fuel.<br />Also, salt water quickly crystalizes inside the motor if it isn't flushed with fresh water after every use, and even then, it still can form. Salt water is also extremely corosive, and can cause the aluminum ports and manifolds to oxidize, forming white popcorn-like growth, that can restrict or completely block the cooling system.<br />Once this happens, the motor must be torn down pretty-much to overhaul state, to remove this stuff. Not to mention the condition it leaves the surfaces after removal.
