Newer era Mercury 4 stroke cooling temperatures

[QBhoy]

Hi…having had a few beers during a lovely first sail of the season today…I’m finding myself wondering around these new Mercury outboard running temperatures. Having had this Merc 115 CT 2.1l engine for a few years now…the first thing I noticed and continued to wonder around, is how cool it runs. It runs around 52 degrees C. About 125 Fahrenheit I think. Seems very cold running to me. But is exactly around what the manual says it should be.
Having been used to either old school outboards or GM inboards all my days…the latter of which, I also own…runs at 150-160 Fahrenheit…the outboard is significantly cooler running.
The thought around this came to mind more prominently again this week when I changed the oil on her. I’ve changed the oil on this many times now and even a couple of times a season too. Each time, there is a slight whiff of fuel in e oil. Nothing serious…but enough to make me wonder around the engine low running temps, perhaps having an effect on such a thing.
Anyone any similar thoughts ?

 

[Texasmark]

I wonder that too since non-marine applications of 4 strokers run around 200F in today's more efficient engines. My 2011 Silverado sits rock solid on 210 and has since new. It has electric fans behind the radiator and they will maintain that temp regardless of what I'm doing.

Other things engines tend to "sludge" up when not run hot enough to boil the water out of the oil and internal parts. Service literature specifies not running engines on short trips, or turning the engine on to move the vehicle and turning it back off, not allowing time for it to come up to temperature. Diesel farm tractors are particularly sensitive to this to the point where the deposits get so bad that they "slobber" carbon, fuel, and water all over you when first cranked after long sitting spells without running.

 

[Faztbullet]

Ya.. but you dont run your truck at 6000rpm down the road either like a outboard.

 

[Texasmark]

Ya.. but you dont run your truck at 6000rpm down the road either like a outboard.

No I don't but what difference does the temperature make if the engine tolerances are designed for thermal expansion at the higher temperatures?

 

[Texasmark]

No I don't but what difference does the temperature make if the engine tolerances are designed for thermal expansion at the higher temperatures?

I had another thought last night. It may be to reduce the accumulation of engine cooling chamber deposits especially from salt water. I live in a high alkaline environment. Great for showering but tea pot accumulates lots of mineral deposits.

 

[Lou C]

There is that issue (people think it’s salt dropping out of suspension but I think it’s actually calcium), and the fact that open or raw water cooling is not pressurized. Pressurizing your cooling system to 15 psi with 50/50 water/antifreeze keeps the coolant from boiling till approx 265* F. In a raw water cooled engine you could get boiling at temps as low as 200*F in the hotter parts of the engine like the cyl heads. This boiling can cause deterioration of metal especially aluminum over time. So it seems that is what they are trying to avoid by running such low temp stats. FWIW I have run a 160 in my old 4.3 raw water cooled and when I replaced the cyl heads I found the expected rust but didn’t find any passages clogged by any deposits; maybe the water here isn’t salty enough, Long Island Sound region, we still do have to replace exhaust systems every 5-7 years though. I actually tried a 140 stat last year and the engine took forever to warm up and I would up putting the 160 back in.

 

[Sea Rider]

QBhoy, if the motor heats up within its tech specs, relax and don't worry. Don't drink too many cold beers or will surely make you wonder again.

The only possible way to know if the motor is cooling right as when new out of the box is to take temp readings with an IR gun at different block's spots when new or fully restored to new condition, keep that info at hand. Will be useful when suspect the motor is not cooling right as used to do specially when runing in salt water scenarios for long years of use. Salt deposits, scale, layers, crusts whatever will reduce yes or yes all the water cooling passages diameters and motor will work much hotter than it should.

Will be amazed at the temp variations readings that will find when comparing new to used motor temp scenarios...

Happy Boating​

 

[QBhoy]

QBhoy, if the motor heats up within its tech specs, relax and don't worry. Don't drink too many cold beers or will surely make you wonder again.

The only possible way to know if the motor is cooling right as when new out of the box is to take temp readings with an IR gun at different block's spots when new or fully restored to new condition, keep that info at hand. Will be useful when suspect the motor is not cooling right as used to do specially when runing in salt water scenarios for long years of use. Salt deposits, scale, layers, crusts whatever will reduce yes or yes all the water cooling passages diameters and motor will work much hotter than it should.

Will be amazed at the temp variations readings that will find when comparing new to used motor temp scenarios...

Happy Boating​

Haha. Found advice on the beers.
The temps are still as they are when she had 18 hours on her and purchased. It’s dead on 52oC when cruising. Around. 53-56 when fast displacement speeds. Just always thought that was considerably cooler than the v8 mpi and all the others I’ve ever known. God curse the smart craft read outs. You become obsessed with watching them

 

[Lou C]

We are all a bit obsessed with details aren't we lol. When I tried the 140*F stat on mine because I had heard for "years and years" that a higher temp stat was guaranteed more or less to cause clogged up cooling passages and resultant overheating, I was obsessed with the fact that it ran at 120* till I got up on plane then it never went over 140* Finally I had to remove the exhaust manifolds to do another job (replace the leaky steering actuator, hope you never had to do that one) and found that, the lower temp stat was causing condensation in the exhaust manifolds. So seeing no real benefit of it I went back to the 160*F stat.
Looking back at the pix of my block and old cyl heads taken apart 5 years ago after 29 years of use and half of that at least in salt water, I see no evidence of clogging, and the engine never ran hot, unless there was another problem causing it. So all the good advice we read take with a grain of salt (pun intended)....
the only thing that resembles a deposit of any kind, is seen on the water ports on the cyl heads, the ones that are at the rear of the engine, where there is little water circulation, show some kind of whitish deposit there. Nothing else to report. Not sure if filling the engine every season at winterization helped reduce corrosion but didn't have a rust through with the old heads, it was blown HGs from a severe overheat which also cracked the center cyls valve seat areas. However the cooling passages in the heads were getting eroded from years of salt water use, to the point where once resurfaced they might not have sealed well against the new head gasket. That and the cracks made it more sensible to replace rather than repair.
After replacing the cyl heads, I added a new center riser exhaust system to replace the NLA OMC one piece batwings and rebuilt the Quadrajet 4bbl and it ran even better than before. I think using a better rebuild kit and the center riser exhaust (less restriction, going from a 3.5" to a 4" outlet) helped.

 

[Sea Rider]

Don't have the least experience with IB motors, would you say that those rude heavier steel blocks which might have smoother water passages collects way less salt buildups in their water passages over the years compared to much lighter OB's alum blocks if had the opportunity to compare ?

Happy Boating​

 

[Lou C]

Could be, it also maybe that the salt/calcium doesn't bond to cast iron in the same way as it might to aluminum, since when cast iron corrodes it constantly flakes off small bits of iron, perhaps limiting deposits.

 

[QBhoy]

Could be, it also maybe that the salt/calcium doesn't bond to cast iron in the same way as it might to aluminum, since when cast iron corrodes it constantly flakes off small bits of iron, perhaps limiting deposits.

Could be right. My main concern is around her getting suitable enough temps to burn the fuel well perhaps. Although I’ll admit…most of the hours spent with this boat are mainly spent at slower speeds. Then again, at slower speeds not planing, she runs a few degrees warmer

 

[Sea Rider]

Then again, at slower speeds not planing, she runs a few degrees warmer

The water pump pumps better pressurized water thru the water passages accordingly to which rpm the motor is currently revving up to to achieve slight more or slight less temp readouts with a temp gauge. To graph that occurence...

At the back of my motor there's a thermo water port that's always exiting more or less amount of water at different temps, when at idle can collect hot watter to prepare a nice cup of Hot tea, whereas at full throttle nope. LOL!!

Happy Boating​

 

[QBhoy]

The water pump pumps better pressurized water thru the water passages accordingly to which rpm the motor is currently revving up to to achieve slight more or slight less temp readouts with a temp gauge. To graph that occurence...

At the back of my motor there's a thermo water port that's always exiting more or less amount of water at different temps, when at idle can collect hot watter to prepare a nice cup of Hot tea, whereas at full throttle nope. LOL!!

Happy Boating​

She’s actually at her coolest at planing speeds all the way up to full throttle. That’s when she runs at 52 degrees C steady. No change now at 1000 hours than she was at 18 hours and purchased.

The water pump pumps better pressurized water thru the water passages accordingly to which rpm the motor is currently revving up to to achieve slight more or slight less temp readouts with a temp gauge. To graph that occurence...

At the back of my motor there's a thermo water port that's always exiting more or less amount of water at different temps, when at idle can collect hot watter to prepare a nice cup of Hot tea, whereas at full throttle nope. LOL!!

Happy Boating​

She’s actually at her coolest at planing speeds all the way up to full throttle. That’s when she runs at 52 degrees C steady. No change now at 1000 hours than she was at 18 hours and purchased.
So about 125F. Compared to the v8 mpi running at 66C and 152F

 

[Lou C]

I think on some Suzuki motors they had the option of a higher temp thermostat for people in very cold regions like northern Canada & Alaska, that was set for about 140*F.
I just find it interesting how many times I read that 140* was the magic number to not exceed in salt water, yet I ran a 160 with normal temps from 160-175 for 20 years in salt water and really never had deposits to any significant extent. One of those marine mysteries I guess.

 

[QBhoy]

I think on some Suzuki motors they had the option of a higher temp thermostat for people in very cold regions like northern Canada & Alaska, that was set for about 140*F.
I just find it interesting how many times I read that 140* was the magic number to not exceed in salt water, yet I ran a 160 with normal temps from 160-175 for 20 years in salt water and really never had deposits to any significant extent. One of those marine mysteries I guess.

Interesting Lou. I’d never even given that notion any consideration. You’ve only got me more concerned now, haha. I live in Scotland and run in a fresh water, almost glacial Loch. Water temperatures range between close to freezing up to about 11-15 degrees C at its warmest.

 

[Sea Rider]

Hey QBhoy I thought that you were boating at open sea and not in a nice scenery Loch, that will account for your motor to be free having water passages obstructions issues as found in salt water, if extremely salty the worse according to my personal experience tearing powerheads on constant basis. Many motor brands have just one thermo factory installed to choose, those motor won't care if boating in warm or cold water environments as long are cooling properly...

Happy Boating​