Why is there 2 different Thermostats available for my Engine

[Westcoaster]

I have a 2013 DF90A and there is a 140f and a 160f thermostat available, now i read most raw water cooling systems typically have a lower temp thermostat than a closed (anitfreeze) system, but why would there be 2 different ones for the same engine ? My engine came with the 140°.

I trailer the boat, use in salt water and flush every day.
Just wondering if maybe the 160° may be the better choice since it will be more efficient, a little warmer, and maybe prolong engine life ?.

There seems to be different opinions on this, but does anyone know for sure why i have a choice ?

Thanks

[Moonlighter]

Good question!

FYI My DF115 runs consistently between 72-75C depending on how fast I run, so i assume that mine has a 70C thermostat. That is here in Queensland, Australia where water temps range from about 15C in winter to about 26C in summer, sometimes warmer in very shallow waters on hot days!

I have emailed my contacts at Suzuki HQ here in Australia and have asked the question. Will let you know what they say.

[Westcoaster]

Thanks Moonlighter
I already asked my small dealer here but they just said "hey look at that, there is 2 different ones"

[catacom225]

Temp

Its all about your geographical zones

[Westcoaster]

I've heard that one as well but nobody seems to know exactly where these zones are, also heard the cold water/warm water theory but what is considered cold vs warm and which thermostat is for where and WHY.

You would think Suzuki would inform dealers as to which thermostat to use and why, but NONE of the dealers i talked to know the answer, there are many comments on the internet on this but most are just theory's and i don't pay much attention to that.

[nelbur]

Back when my DF 140 was new there was only one thermostat for it, the cooler one. During the break in period, many of these engines including mine had a problem of "making oil" which was a build up of gas in the oil. I believe the higher temp. thermostat was to get these engines hot enough to evaporate the gas from the oil. I have recently installed the hotter thermostat in my engine even though it had stopped making oil some time back, because I think the higher temperature is better for engines.

[Moonlighter]

As i understand it, our 4 stroke marine engines generally operate at a fair bit cooler temps than their automotive ancestors.

And yes, the comments about making oil when running too cool have been widely reported. A Good reason to never leave the thermostat out of the engine!

Havent heard back from my Suzuki contacts yet. Be interesting to hear what they say. Will post here if/when i hear anything.

Westcoaster, where are you located?

[Westcoaster]

Vancouver B.C.
Canada

[Seaduck]

I replaced mine with the cooler stat. Might order the higher stat to see how the motor runs. Im in virginia

[redlowrey]

Back when my DF 140 was new there was only one thermostat for it, the cooler one. During the break in period, many of these engines including mine had a problem of "making oil" which was a build up of gas in the oil. I believe the higher temp. thermostat was to get these engines hot enough to evaporate the gas from the oil. I have recently installed the hotter thermostat in my engine even though it had stopped making oil some time back, because I think the higher temperature is better for engines.

Mate your way off the track, as I stated a couple of years ago on this forum the only way fuel can find it's way in the sump was through the low pressure fuel pump or the vst and most times it was the vst. The reason for different thermostat temperature's is obvious, the colder the water you would use higher temp opening thermostat.

[Westcoaster]

The reason for different thermostat temperature's is obvious, the colder the water you would use higher temp opening thermostat.

Would you care to elaborate on this please ?
To me it still doesn't make sense, the engine will warm the water up no matter if its 3° or 20° . Until thermostats opens they are all equal ( just sitting there closed) , its just a matter of when it opens to maintain a given temp, so my question is still the same one, WHY is there a 60° and a 71° ?

[Moonlighter]

Well, I have spoken to my local dealer. He told me that in Australia, our standard thermostat is usually the 60C version, but on some of the latest Lean burn engines, they have a 55C version as standard here.

Asked a mate of mine who is a professional performance engine builder, he said that you would use the 60c in hotter water temps, like in temperate areas such as we get here in Australia. He mentioned that its not all about operating temp, but also water flow - the 60c thermostat opens earlier and produces more water flow sooner ie. initial cooling for quick starts. He said that regardless of the thermostat fitted, the engines will probably still run at similar operating temp when they are at speed.

So there we have it.

[redlowrey]

I fish in the bottom southwest corner of Victoria Australia and the water temp ranges from 12c to 20c and I use 71degree thermostat and I use 15w40 not 10w40 in oil. If I was fishing in water 20c or more I would use the 60 degree thermostat and 20w50 in oil. When the water is warm it takes little effort to get to operating temperature, but when it is cold it takes a lot of effort to get to operating temperature and if the thermostat opens early it takes a lot more time to get to operating temperature. Remember the engines are fuel injected and the ecu is looking at water temp for iac and injector pulse width modulation. In your case 71 degree thermostat.

[Moonlighter]

I fish in the bottom southwest corner of Victoria Australia and the water temp ranges from 12c to 20c ....

On the same day?

[Westcoaster]

Well thanks for the feedback guys its much appreciated.
Interesting topic to say the least, i never found any info from Suzuki themselves, only what is listed in my service manual for thermostat operating temp (58c – 62c (136f – 144f), i would still be interested in hearing their take on all this. I did some probing around and found that a lot of newer Suzuki's offer a 50c or a 71c thermostat, and that the DF20A for example only has a 50c stat with an operating temp between 118f-125f, pretty cold i thought, so after seeing that many engines are running much cooler 140f doesn't sound so cold anymore.

I ran my engine (in the driveway) today for the first time in 3 weeks, i had my plotter hooked up as always so i could monitor things more accurately since my motor is interfaced. I have the 60c stat and on startup the temp climbed up to 147f then i believe the stat opened fully, after a few min's it stayed right at 138f just idling away the whole time, i sure love this engine so far, fuel burn dropped steadily from the initial .22 and eventually sat right at .16 gp\hr .

All this talk on the net about crystals forming in your engine while running hot or cold is complete bull, the salt deposits only begin to form after shutting down and the water drains out, whatever doesn't drain out evaporates for the most part and deposits are then left behind, so my interest is merely what is a better operating temp for my motor health wise ( and i don't know the answer to that), other fellows with the same boat and motor but with the 71f stat are getting roughly 160f at cruise ( mine runs 139-143 ish cruising 4500 rpm), so it seems there is a difference other than startup/warmup. Maybe at WOT the 2 stats wouldn't make as much of a difference but i don't run there hardly ever so...
For now i'm going to leave the current thermostat in there, maybe when its time to replace it i'll reconsider using the 71c stat.

redlowrey..i found it interesting the seasonal water temps where you live are only slightly warmer on average than mine here in Vancouver.

here is a global animation from from January 1985 - January 2007
https://www.youtube.com/watch?v=vTig9gKegQk

here is the temperature color scaling chart for the above video
might have to zoom in to read it.
http://www.ospo.noaa.gov/data/sst/co...l_small.cf.gif