Normal Engine Temp Range for 4s 60hp Merc OB -vessel View ??

[Canufixit]

Hi all, 2 + season old 60 hp Merc 60hp 4 stroke Bigfoot on an 18' pontoon Fresh water Pond with minor weeds in New England. .Runs great but have had an over temp alarm twice - at high speed.


I Hooked up my vessel View and I'm getting a wide range of readings for temp. Idle 120F. Full throttle runs 138 to 150 - but "sometimes" climbs to 160 then drops down to 140 - 150F range. I do do a lot of low speed cruising. Hours on engine about 400. Checked for weeds on Lower unit - ok. And, I just hose flushed the engine.


For Reference - what is the "normal" range of temp 120F (therm opening) to what?? What is the Temp the engine triggers over temp alarm ??


I will today change the thermostat and I have a merc water pressure tester on order for delivery next week.


My experience thinks it's one of the following - blockage, thermostat, sensor or impeller. In my OB experience, over many years, tells me that the Impeller "should" be at least 3 years to 5 plus of service. And, I cannot see how a bad impeller can "sometimes" work fine at high speeds. IT is usually good, going bad, or crap - but not inconsistent. Sensor failure is possible but not probable. My clean flush indicates no blockage and I have not gone though mud or sand waters. That leave me thinking a possible sticking thermostat ?? .


So ... For Reference - what is the "normal" range of temp 120F (therm opening) to what?? What is the Temp the engine triggers over temp alarm ??


Any comments on the cause ???


Thanks All !!
SteveC

 

[Texasmark]

On 2 strokers of that HP, the stat ranges from 100-143F, engine and year dependent I'd assume, while the alarm is 195F.....both devices have their operating tolerances of probably <10%.

Inlet holes are deliberately small and numerous to aid in prevention of weed ingestion (assumption). Water pressures run up to 15# at high RPMs on 2 strokers which isn't all that much to flush out a weed that got in the wrong place....Tell Tale to name one. On a T stati it would be more apt to keep the stat valve cracked open rather than shut, course a lot of weeds might get caught in the supporting bracket of the stat and clog it.

 

[Canufixit]

On 2 strokers of that HP, the stat ranges from 100-143F, engine and year dependent I'd assume, while the alarm is 195F.....both devices have their operating tolerances of probably <10%.

Inlet holes are deliberately small and numerous to aid in prevention of weed ingestion (assumption). Water pressures run up to 15# at high RPMs on 2 strokers which isn't all that much to flush out a weed that got in the wrong place....Tell Tale to name one. On a T stati it would be more apt to keep the stat valve cracked open rather than shut, course a lot of weeds might get caught in the supporting bracket of the stat and clog it.

Thanks Tex! You eluded to specs .... I did find these for 4S 50/60 hp. For others should they need. You are pretty much on target.

From the Merc 4s service manual 2K+ ;

- Thermostat cracks opens at 118-123F.
At 145F the thermostat should open min .120" /3MM

Water Pressure
@1K RPM ~ 5.75 PSI .... MAx out at @6K RPM 20.25 approx.

SO I'm thinking as you stated ....

120f to 145F should be fine as the thermostat is ranged for this. Water Boils at 212F so ... " Theoretically "

above that ??? I'd assume getting close to 200 would be max for alarm. However, Merc may play it safe and trigger the alarm / Guardian mode well below ... Guess - 180f ??

But ... I'm still searching for the "Mercury" spec for the allowable normal range and alarm trigger ....

SteveC

 

[Canufixit]

Ok, Found something .... But the only location I can find this is in a Russian site?? But this looks like a great document .... ??

Outboard FourStroke IITechnician’s Guide

90-898313

Page 103 ...


Overheating ControlWhen the engine speed is less than 2,000 rpm, this control mode is delayed60 seconds after the engine is started. When the engine speed is 2,000 rpmor more, this control mode is delayed 20 seconds after the engine is started.The engine is considered to be over-heating if its temperature increases from167° F (75° C) to 185° F (85° C). If its temperature exceeds 194° F (90° C),this control mode begins. The overheat warning buzzer sounds, and theignition and injection are cut according to the misfiring rate.If the engine overheats, the ignition of both cylinders #1 and #4 is cut,however the ignition of cylinders #2 and #3 is not cut. After the enginetemperature decreases to less than 167°F (75°C) the overheat warning canbe cancelled by decreasing the throttle opening angle to less than 2° andturning the ignition key to the off position.


Comments ???

 

[Texasmark]

1st.... my Chevy Silverado sits on 210F and doesn't move regardless of conditions...electric therm. controlled fans...unless I just started it and it hasn't warmed up. Farm tractors run 190F give or take, temp moves around, belt driven fan but run hot. 4 stroke engines.......I guess 4 stroke OBs run hot too; different engine design, different requirements, and there are always the emission reduction reasons...hot burns cleaner. What you are describing is a "limp" mode that would allow you to limp back to the dock, under your own power if you had a thermal problem in the engine. Obviously lots more gadgets on 4 strokers.

 

[Canufixit]

1st.... my Chevy Silverado sits on 210F and doesn't move regardless of conditions...electric therm. controlled fans...unless I just started it and it hasn't warmed up. Farm tractors run 190F give or take, temp moves around, belt driven fan but run hot. 4 stroke engines.......I guess 4 stroke OBs run hot too; different engine design, different requirements, and there are always the emission reduction reasons...hot burns cleaner. What you are describing is a "limp" mode that would allow you to limp back to the dock, under your own power if you had a thermal problem in the engine. Obviously lots more gadgets on 4 strokers.

But ... 4 Cycle (auto, truck, etc.) have pressurized cooling systems (15 psi radiator caps?) - this raises the boiling point from 212F to Much higher (250F ish ?). Many Auto thermostats do not open until approx 200F - as that's the "non Cold" or min desired operating temp. The MErc thermostat opens at 120F. If Merc wanted the engine to run hotter - they would have increased the thermostat cracking temp .... Merc non pressurized cooling will boil around 212F.

And, My Guardian alarm sound off well under 200F. Multiple Blogs on 4S Mercs with Temp listed reading tend to agree,

SteveC

 

[Texasmark]

All I'm saying is via this discussion it seems that 4 strokers are designed to run hotter....maybe it's due to EPA clean air requirements. Just trying to justify the why 2's and 4's seem to have different ranges.

 

[Canufixit]

All I'm saying is via this discussion it seems that 4 strokers are designed to run hotter....maybe it's due to EPA clean air requirements. Just trying to justify the why 2's and 4's seem to have different ranges.

Thanks Tex! Did not mean you were shooting form the hip ! Just trying to justify my thoughts and leaving an info trail others can search for ....

Still looking for confirmation for actual temp reading from a 4s 40hp owner ...

SteveC

 

[Canufixit]

OK, I apparently have a solution .... I changed my Thermostat and it appears to be running fine. As for my original question ... What's normal Operating Temp for 4Stroke 2018 60 hp Bigfoot... Remembering that Local Temps, Water Temps, water flow from pump , and possible intake port interference (i.e. weed pick up) all vary - I found the below temps with my new Thermostat (My Impeller I consider Ok at 2.5 years old but I have not yet done a pressure test yet ...);

Warms to 120F. Under 3K RPM stays around 120 - 124F. 3k to 4k temp does rise into 130F range. 5600 RPM it ranges from 135F to 145f and tends to bounce a little - possibly due to weed pickup on lower unit ... Never went into 150F range.

IF possible next week I'll do an impeller pressure test and advise if my Impeller flow is acceptable.

Thanks All !!