6.2 Mercruiser Temp

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Brian Suhl

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exMember
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May 9, 2001
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4517
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168
Just bought a 2006 Searay with a 6.2 Bravo III with only 63 hours. At an idle the temp gauge reads 110 and the Smartcraft digital display is the same. At 3200 rpm the temp will get to 125 but not higher. Water pump seems ok with 8psi at 3200. This is a fresh water boat always stored indoors and perfect condition. Should I replace the thermostat or are these temps ok?
 
Fresh water or raw water cooled? If it's raw water cooled, you may have a piece of sand or something keeping the thermostat open. 125 is not good. The engines need to get up to operating temperature.

You can take the thermostat out ans see if it's closed completely. Get a gasket before you open it up. If it's been on there for 8 years, you will likely damage it when you take it off. Assuming the temperature gauge is correct.
 
Thanks and yes it is raw water cooled. I seem to recall Mercruiser had some spring loaded ball valves in the thermostat area. This is from years ago but people refered to them as ping pong ball that did something for flow. I'll have to read more.

I think I'll order a thermostat today.
 
160 degree would be correct for raw water cooled, not slain salt water. If you were in salt, then 140 degree would be correct.
 
Agree with 160* which ours calls for even though it's RWC in salt water. With RWC but running in fresh, Brian should be in good shape. A 140* won't put the Electronic Engine Controls under full management.
 
You might try aiming an IR temp gun at the thermostat housing and temp sender area when the engine has run for a good while as a reality check against the gauge reading. If they still match , check to see if for some reason the t-stat was removed and not reinstalled.

Gregory - Are sure about the salt and 140*F t-sat for the injected FWC engine?
According to the parts list Merc RWC injected 6.2L apparently takes a 160*F .
Doesn't mention salt or 140*F like the old (pre-Vortec?) RWC carb engines had.
(The FWC version lists a 170*F t-stat.)

http://www.marineengine.com/parts/m...1a090000-thru-1a092168/thermostat-and-housing
http://www.marineengine.com/newparts/part_details.php?pnum=MER807252T+2
http://www.marineengine.com/newparts/part_details.php?pnum=MER864493
 
Sandy, I didn't say 140 degree in salt for FWC. He's RWC. I didn't say anything about FWC. I guess they don't worry about salt crystallization in the newer RWC engines with the higher temps.
 
quote:
Originally posted by Sandy

You might try aiming an IR temp gun at the thermostat housing and temp sender area when the engine has run for a good while as a reality check against the gauge reading.

Click to expand...


Absolutely.

My starboard gauge is way out of whack. IR readings show both engines to be in spec. There is a lot to be said for mechanical vs. electronics in this case.
 
I will try the IR gun. I suppose both the dash gauge and the Smartcraft digital readout likely use the same sensor.

Thanks for the help guys!
 
quote:
Originally posted by Gregory S

Sandy, I didn't say 140 degree in salt for FWC. He's RWC. I didn't say anything about FWC. I guess they don't worry about salt crystallization in the newer RWC engines with the higher temps.

Click to expand...


Very sorry, that was a typo mistake by a thick empty noggin . I intended to peck out "RWC" instead of that FWC.
For just the reason j-d explained, above I "think " the RWC 6.2 requires a 160* to keep the ECM sending out happy thoughts after getting ECT sensor temp-variable voltage input .
I don't know of any injected/ECM controlled engines that use the carb 140*, but that certainly doesn't mean there are none.
There just does not appear to be any 140* t-stat parts-listed for the 6.2L .
 
quote:
Originally posted by Brian Suhl

I will try the IR gun. I suppose both the dash gauge and the Smartcraft digital readout likely use the same sensor.

Thanks for the help guys!

Click to expand...


That may not be the case. The Smartcraft would copy some of the ECM (ECU)'s data stream and get coolant( engine RW in this case) temp from the ECT sensor. Not sure, but I think there is likely a separate gauge sender . Logic is, an ECT could not be used with dual station gauges, not the dual station sender( 1/2 resistance of std. sender) with the ECM.
 
In salt water raw water cooled this is more or less a chronic problem. I have replaced stats but after about 1-2 seasons they tend to get stuck open slightly. One thing you can do before replacing it is this: Run the boat up on plane so it gets up to temp (at least 160* on the gauge) and then throttle back, before the engine temp drops get a small hammer and tap on the thermo housing. This can dislodge a piece of rust in the thermo seat and it may close all the way when it needs to and restore your proper operating temp. I do this before replacing a stat. If it does not clear it up then replace the stat. The only cure for this issue is closed cooling LOL....
 
Gotcha Dave. HF hasn't had the under $20 IR gun for a while. Last sale price was $24.95[:P]
 
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