overheating at low idle

[LANALOU]

I have a 1997 johnson 15 hp mounted on a 12 ft smokercraft alaskan that i just purchased. at any rpm less than 1200 or 1300 after a short time in forward gear the hot alarm starts beeping intermittantly. i can increase the rpm to about 2000 plus and after a short time then it cools down and the alarm goes off. i am new to boating and would like to know if this is common or if the motor should be able to troll at 1000 rpm or less for any length of time. it doesn't seem to overheat when not in gear and just idleing

 

[12Footer]

Re: overheating at low idle

Welcome to iboats,Lanalou.<br /> This is a sign the impeller is probably starting to go.They wear out in two years or so normally.

 

[Boatist]

Re: overheating at low idle

Does that engine hav a PEE hole where the water squirts out the back. If it does should squirt any time motor is running. Water pumps last 10 years or longer unless you run motor out of water or in the mud or sand. Water pump works two ways on that motor. AT low RPM is a displacement pump at hig RPM is a centrifical pump. If someone has started it out of the water for ever 1 minute likely impeller ends melted off so will not work as a distplacement pump. Good Luck

 

[fireman 757]

Re: overheating at low idle

these guys have hit it on the head. Replace your impeller in the water pump. It's about 13 dollars.

 

[LANALOU]

Re: overheating at low idle

thanks for the feedback, will replace.<br /><br />great forum