Running hot 180 on a 160 thermostat??????

[sebas54]

Mercruiser v6 4.6l alpha 1. running 180 on muffs. New impeller & housing, new thermostat 160, new water pump circulator, new temp gauge and sending unit.

I have checked the wiring from the sender to the gauge and its good. The only part of the motor that is hot is the thermostat housing??? Once the motor is off for 30 seconds the temp goes down to 160 or less?

Please help??

 

[1ruralmailman]

Re: Running hot 180 on a 160 thermostat??????

sounds to me like you got a bad,or missmarked t-stat.did you put it in a pan of water and heat it while checking the temp before installing it?be the first place i would look.

 

[aldfaa]

Re: Running hot 180 on a 160 thermostat??????

I recently replaced my t-stat with a180 as well. With a digital gauge I am displaying 175 at idle on the muffs. Open it up to 1,000rpm it drops 165.

In the lake it runs about 165 unless at idle then it goes to 170. The higher the RPM the more water that will flow through the system.

under what conditions are you seeing the temp this high? On my 96 5.7 I once installed a plastic spacer and the t-stat in the wrong order which caused an overheat. Didn;t figure it ot untill I looked at the booked.

 

[lg260ss]

Re: Running hot 180 on a 160 thermostat??????

It is possible that you aren't getting enough water to the engine on the muffs. I've had that happen in the past. 180 isn't hot enough to hurt anything anyway. Put the boat in the water and it could be fine.

Why did you replace the thermostat? I have never seen a stat go bad in any vehicle or boat I have owned. It always ends up being something else that causes a high temp issue.

 

[joncrisler]

Re: Running hot 180 on a 160 thermostat??????

It is possible that you aren't getting enough water to the engine on the muffs. I've had that happen in the past. 180 isn't hot enough to hurt anything anyway. Put the boat in the water and it could be fine.

Why did you replace the thermostat? I have never seen a stat go bad in any vehicle or boat I have owned. It always ends up being something else that causes a high temp issue.

Interesting- I have had 2 thermostats go bad on my boat- the pin actually broke through the metal, so although the bimetal worked, the pin was not pushing against anything, so it stayed shut. Both Merc or Quicksilver brand. I also had a new car with a thermostat that was defective from the factory- it was stuck wide open. Car would never get up to temp. Under warranty, they replaced the gauge, sending unit, water pump and a few other things, but never tested the lowly thermostat. Eventually we gave up and kept driving it, then one day when the temp was over 100 F, the temp gauge actually moved above its lowest level (100), proving it all worked. I pulled out the thermostat and found it stuck open.

 

[Philster]

Re: Running hot 180 on a 160 thermostat??????

Using 160 T-stat doesn't mean the engine will run at 160. 180 isn't very 'hot'... given that 170-175 is pretty much an ideal range.

 

[boat1010]

Re: Running hot 180 on a 160 thermostat??????

160 is just the temp that it opens. It doesn't mean it will run at 160. 180 isn't a bad temp to run...

 

[Philster]

Re: Running hot 180 on a 160 thermostat??????

I know there is this debate over running salt water through a 180 degree engine. It can speed up scaling. However, a perfectly clean, perfectly new boat with no wear has a shot of running 160-170 all day and night. As a boat ages, 175 would seem normal. 180 is warm, but not hot, and no metal is being damaged per se. I know that on boats a few years old, 170-175 is well accepted. Then you've got gauge accuracy, etc.

I would want to see some results from actually running the boat on the water. 180 on muffs seems high.

 

[JWebber]

Re: Running hot 180 on a 160 thermostat??????

Yes this is true, thermostats are a passive control valve that maintains temp control. Pull it out and watch your gauges and see the diffrences.

 

[sebas54]

Re: Running hot 180 on a 160 thermostat??????

Thanks for all the info. The engine always ran at 160 until I replaced the impeller(burned it running the engine without the muffs). I just bought a temp. gun so i will see what that reads. I had this problem before and after extensive trouble shooting I replaced the thermo housing and it ran at 160 again. If there is no damage being caused, running at 170 -180 then I am a very happy man and will end this fiasco and let it be.

I also bought a 140 thermo and will install that tomorrow and check the old one.


Thanks again.

 

[sebas54]

Re: Running hot 180 on a 160 thermostat??????

Just finished removing 160 thermostat, tested it and it worked. Checked the temp with a temp gun/laser (on muffs), gauge says 170-180, temp guns says 160 but the hottest part was the "new" circulation pump. Changed the thermo for a 140 for the hell of it and now it runs at 160. Checked again with the temp gun and it reads 145- 150, again hottest part was the circulation pump??????? Any Ideas?

Thanks