85 Merc 140- normal operating temp?? or am i overheating??

[webnetxpress]

just trying to get a boat in the water for the first time in about 2 years. I've been going through it and replacing all rotted out or old components. I replaced the impeller this week. yesterday I started it up (in the driveway with the water muffs on) and began to set the timing, dwell, idle, mixture, etc. I finally got it running good but then it seemed to start to overheat. I'm not sure if it was because the overflow tank was empty to start with? or it was just plain old overheating...<br /><br />Anyway, what is the normal range of temp for this engine?<br /><br />I have plenty of oil pressure, a full coolant tank, a new impeller and no noticeable leaks anywhere. <br /><br />So, if it's overheating what would I look at- the thermostat?? <br /><br />Thanks, Dave

 

[denniz]

Re: 85 Merc 140- normal operating temp?? or am i overheating??

175-180 degrees is normal but I doubt youd get it that hot on a hose.

 

[J.J.W]

Re: 85 Merc 140- normal operating temp?? or am i overheating??

Dave,<br />It sounds like you might have what most people refer to as a 470 mercruiser. I don't belive the 140 came with closed cooling. If the heat exchanger is full of coolant, and the overflow resevoir is not, it should run fine temp wise. I believe they had a 160 degree thermostat in them from the factory. Most that i have seen run right around 170 degrees. If its running much hotter than that you need to look at the thermostat and also the heat exchanger. You can remove the endcaps from the heat exchanger to get a good idea what it looks like inside.<br />Good luck,<br />Justin<br />justin@sterndrive.cc<br />www.sterndrive.cc

 

[webnetxpress]

Re: 85 Merc 140- normal operating temp?? or am i overheating??

yes, sorry it was early when i typed it, it's a 170 (3.7l, aka "470") engine. It has the closed cooling circuit and the stern drive water cooling circuit.<br /><br />I'll put a new thermostat in it tonight (cheap enough for peace of mind) and then go from there. <br /><br />Thanks.