third time not a charm

[mmwest]

I've had three t-stat replacements since may from marine max,got boat out of shop and take it out today --temp reads 170 degrees for 20 min. then back down to 130 deg and thats the crap it's been doing since i've started w/this problem. Does any one know what could be going on. THANKS

 

[mmwest]

Oh yea,what is the worst that can wrong running at such low temp.

 

[JediJD]

Are you certain the temperature readings and gauge are accurate? Have you hit the manifolds with a laser temp gun ($15 or so on eBay) to see if the temps are in fact changing downward thirty degrees? Temp sensor perhaps?

 

[mmwest]

thanks ,i'll check it out like that.

 

[springer3]

Marine Max may have a bad batch of thermostats. Laser pyrometers are fine if there is no other way, but IR accuracy depends on the color and the surface condition of the target, and the errors are much larger than the small change you are attempting to measure (I work in a lab and do both IR and thermocouple temperature measurements).

The better way to check a thermostat is to put it in a pot on the stove and slowly bring up the temperature. A double-boiler type is best, because the heat from the burner does make the bottom hotter than the top. Hang the thermostat at the same level as the thermometer, and you will get an excellent read. BTY, the kitchen digital thermometers are very accurate, and much safer than glass thermometers.

Your problem does sound like the temperature gage is reading low. It is common to see the temperature drop right after the thermostat opens.

The harm in running too cold? Short-term you might get slightly less fuel economy. Long-term, more fuel and water vapor will accumulate in the crankcase because the oil does not get hot enough to drive off condensed liquids. Condensed liquids collect if the engine sits, and when the hot blow-by gases get into the cold crank case during cold stards. Especially if you use extended oil-change intervals or use the boat for short runs, you will see slightly more engine wear because of degraded oil. You could also see more internal corrosion in the engine.

I would make sure the engine is really getting up to temperature. If the gage reads low, but otherwise works, you can live with that as long as you remember that normal on the gage now means you are over-heating.

 

[mmwest]

thanks for the advice,what really upsets me is i've already paid these people and the've had my boat seems like ever other weekend, plus this is a warranty matter so i feel they need to do it right,i'll probably take it back in eary august. thanks again

 

[Slippery When Wet]

Are you certain the temperature readings and gauge are accurate? Have you hit the manifolds with a laser temp gun ($15 or so on eBay) to see if the temps are in fact changing downward thirty degrees? Temp sensor perhaps?

Any recommendations? I see them on eBay ranging from $18.99 to $48.99...and one is $150. I want to buy one of these,but don't want to waste $20 on a cheap POS,nor do I want to overspend either.

Sorry for the thread hijack.

 

[JediJD]

Marine Max may have a bad batch of thermostats. Laser pyrometers are fine if there is no other way, but IR accuracy depends on the color and the surface condition of the target, and the errors are much larger than the small change you are attempting to measure (I work in a lab and do both IR and thermocouple temperature measurements).

Springer is spot on. My suggestion with the IR gun was to "laser" the manifold when the gauge said 170 degrees, look at the reading, then laser it again when it said 130 degrees. I wasn't suggesting that you actually determine the temperature, but get a SWAG about the accuracy of the gauge and sender. If the thermostat isn't holding temperature it isn't the end of the world (lots of old school guys pull them and leave them out) and the consequences (as eloquently outlined by Springer) are insubstantial in the short run, but problematic in the long run. Later model engines require temperatures to be in a fairly controlled range for optimum operation, so the days of just throwing away the thermostats are over. It does sound statistically odd to me that you would get consecutive bad thermostats, though...even from MM.

By the way, I may get thrown out of the "really nice tool club" for this, but I am perfectly happy with my $10 Centech Harbor Freight IR model. It may not be perfectly accurate, but my guess is that it is within a couple of degrees and usually I am looking for substantial changes, or temperature ranges.

 

[mikebrown123]

Not to threadjack, but these are interesting thoughts which makes me have to ask what the 'normal' temp should be for my 2005 180 Sport?

From that little I have used it so far, it looks to normally be around 165f-170f.

Does this sound 'normal'?

 

[OldSkool]

Not to threadjack, but these are interesting thoughts which makes me have to ask what the 'normal' temp should be for my 2005 180 Sport?

From that little I have used it so far, it looks to normally be around 165f-170f.

Does this sound 'normal'?

You are in the zone. Nomal is between 165 and 195. Depending on the thermostat installed.

 

[OldSkool]

Any recommendations? I see them on eBay ranging from $18.99 to $48.99...and one is $150. I want to buy one of these,but don't want to waste $20 on a cheap POS,nor do I want to overspend either.

Sorry for the thread hijack.

Unless you are setting fan speeds on hydraulic pump drive coolers you don't need a $120.00 unit. Stay medium grade for dependability or go cheap for ball park reference. I use a $50.00 model for all around use.

 

[skibum]

Ask MM to swap the temperature sending unit(s) with known good unit(s) and take it for a ride. Senders fail, too...

 

[skolbe]

What started this issue? Did you get in some shallow water getting sand in the motor. If so, the engine needs to be flushed - otherwise you will keep getting thermostats stuck open. You do not want to run your motor cold for extended periods, you will build up carbon in the motor. My dock neighbor did this for 2 years. When he cleaned the carbs with carb cleaner, sheets of black came out of the exhaust. The entire marina looked like the gulf.

 

[mmwest]

thanks for the replies.currently waiting on response from MM---it's turned out to be a big issue now.

 

[OldSkool]

thanks for the replies.currently waiting on response from MM---it's turned out to be a big issue now.

We took the time to reply now tell us the rest of the story.:smt001

 

[fwebster]

Mercruisers used to have a bypass in the thermostat housing. If it stickes open the engine will run cool. I am not familiar with newer EFI engines, but this one may be being misdiagnosed.