More help with temp problem-gctid389741

[Guest]

My 98 2355 5.0 Chevy temp alarm chirps on and off all the time. When I disconnect the temp switch on the thermostat housing is stops.

I,ve changed the thermostat. the impeller and the switch No joy. My gage says 175 degrees but the thermostat is a 160. Is my engine running to hot? What is the set point of the switch? What should I do next?

Thank you

[Guest]

I'm going through a similar issue, posted today as well.

How are your manifolds/risers?

I would see the temp guage fluctuate when trolling and alarm at the 175ish..

I found water in my # 3 cylinder from a leaking manifold. Struggling w/my re-installing my outdrive presently, but I will post if my steps have corrected the intermittent alarm condition.

Do you have an Infrared temp guage? They are really handy in troubleshooting temp related issues ( and determining if your frying pan is at 350 :-) )

Good luc

[Guest]

After alittle research I Beleive that 175 is a little to hot so now i think that there is a flow problem. My engine temp stays at 175 all the tine ,slow or fast Any thoughts?

[Guest]

How do I back flush the engine?

[Guest]

If you have closed cooling, then 175 temp is right where you want to be. A 160 degree thermostat just means that it opens at 160, not that the temp should be 160. Again, if you have closed cooling, then it just sounds like a sensor issue - you're NOT overheating.

[Guest]

I have an open cooling system Does the engine have a water pump or is the impeller the only pump?

[Guest]

seasam wrote:
I have an open cooling system Does the engine have a water pump or is the impeller the only pump?

Your engine will have a circulating pump that moves water within the engine. Depending on the type of outdrive the impeller could be in the drive itself or mounted on the engine. An impeller or raw water pump pulls water from outside of the boat into the engine.

[Guest]

seasam wrote:
I have an open cooling system Does the engine have a water pump or is the impeller the only pump?

If by "open cooling" you mean raw water cooled, then yes you're overheating. You should only have a 160 degree thermostat if you have closed cooling... are you sure you know the difference between closed vs. raw water cooling?

You have two pumps: one is a circulating pump to run water through the block, and the other is either a drive-mounted (i.e., Alpha 1) or engine mounted (i.e., Bravo).

[Guest]

seasam wrote:
My gage says 175 degrees but the thermostat is a 160. Is my engine running to hot? ...

A 160 deg thermo starts to open at 160, no guaranteed to be fully open until 180. Check the specs on your engine - as the others allude, 160 sounds a little high if you don't have a heat exchanger closed cooling system.

[Guest]

My cooling system is a raw water cooling, takes water from the lake through the engine, no heat exchangers. So this will have two pumps, The Impeller in the lower unit and a circ. pump, belt drivin on the engine? The parts book said a 160 thermostat and when i changed it the old one was a 160.

[itsabowtime2]

Have you check the temp with a Infrared Temperature Gun? If not they can be had for about $30 from Harbor Freight.

http://www.harborfreight.com/catalogsearch/result?q=infrared

I check mine every so often vs. the gauges because gauges can be wrong. I check the manifolds, risers and blocks.

According to spec, 170 is not overheating. However, you first need to determine if that is indeed what your engines are running at. My engines are sea water cooled as well. Replaced the thermostats 3 years ago. I am 99% sure they are not 160 but 140 degree.

[Guest]

Let me restate the facts. 98 5.0L Chevy, Carb, Raw water coling Temp gage is at 175 all the time fast or slow. Replaced thermostat with a 160 that i bought from a marina and they looked up and said 160 was right. All info on line also says that a 160 is right. Old one was a 160. Replaced Impeller on lower unit. Replaced the temp switch. The alarm chirps on and off when this swich is connected. The sender to the gage is not the same as this switch and will not sound the alarm on an over heat ,that is what the switch is for. Others online with the same engine and thermostat tell my there temp are no higher than 170 therefor I think I'm a little to hot. I thank all who reply and please keep replying as all info helps my understand

[itsabowtime2]

Here is a thought, for what it is worth.

My boat has the 5.0L Carb engines as well. My engines run at about 155 each (based upon the gauges) and depending upon where I aim the gun, 148-160. I run the 140 thermostats. I suspect if you were to switch, you would see a drop in operating themerature. It may be worth the small investment in $$ to see.

As an FYI, it looks as if either thermostat is acceptable to run, as the engines are listed for both the 160 and 140 degree stats.

[Guest]

seasam wrote:
Let me restate the facts.... The alarm chirps on and off when this swich is connected. ....

The temperature alarm would probably not go off until your engine temp is over 200 degrees. If it is chirping then it is either a sensor or connection problem. Don't forget your oil sensor and outdrive oil reservoir sensor.

[Guest]

When you replaced the impeller in the lower unit was it coming apart or was it still all together? Has the boat primarily been used in salt water or fresh water? Assuming the gauge and the overheat alarm are reasonably accurate, the most likely cause for the high temperature is some form of blockage. If the impeller was coming apart the pieces from it can lodge in the risers. If used primarily in salt water, you may find the ports in the exhaust risers that exhaust the raw water into the bellows are partially blocked. Finally, there are rubber exhaust flappers just below each riser bellow which help prevent backwash of water into the engine. These get brittle with time and may have come apart and dropped into the exhaust horn the routes the exhaust overboard. Sometimes these problems can be found by determining how hot each exhaust bellow is below the risers.