THERMOSTAT FOR M-25

[PAUL T.]

HELLO TO ALL!!!!  It's been a while since I've been on the Message Board.   Question????  A friend of mine has his CAT-34 down in LA PAZ mexico. He E-mailed me that he needs a thermostat, I think I read somewhere that you really don't need a thermostat, especially in warm water. Engine is M-25. THANX FOR THE FEEDBACK!!!!!!    PAUL

[Stu Jackson]

Paul, welcome back, we just discussed this:  See Reduced engine heat to hot water heater:  http://c34.org/bbs/index.php?topic=3133.0  Read the whole thread -- it's long.  Also, a search on thermostat gets you there.  Don't forget to order the gaskets.  You can call the Livermore dealer from anywhere in the country.  Buy him the thermostat, his engine will like you.

[Ron Hill]

Paul : If you go to a Kubota tractor dealer, you can order a 160 degree thermostat part# 19203-73010 for his M25 at 1/3 the cost of going to Universal!!
A thought!!   

[windrunr]

The Universal replacement thermostat is 180 degrees while the Kubota is 160 degrees.  Universal recommends that the engine have 180 degree thermostat. 

Is there any advantage to keep the 160 thermostat or repace and increase the operating temperature to 180? 

I know on my engine the heat exchanger stays cool to the touch and not worried about salt crystallizing.

[Stu Jackson]

windrnr

Suggest you read the referenced thread in my post #2 above, should answer your question.  Your engine, your choice   

[Ron Hill]

Wind : The Universal thermostat is 160 Degrees and that's what the engines originally come with.  A 180 degree is also available for engines that are used in a COLD area.   

[Mike Denest]

I needed a new thermostat pronto and went to the local Kubota dealer.  He didn't have the 160 degree but he did have the 180 degree.  I installed it and ran the engine, temperatures still looked good. 

[David Sanner]

I'm running the thermostat that starts to open at 180.  In the 50 degree SF waters
(with a clean 3" heat exchanger) my temperature never moves a degree above 180.

Seem to me that the operating temperature is the key number and 180 seems better
than 160.  If you're in warmer water maybe the 160 makes more sense as well
as the 'default' thermostat.

I was just reading this article http://www.oceannavigator.com/article.php?a=9610
which near the bottom the contributing editor makes some interesting comments.

"Regarding the thermostats used on some Universal diesels, nearly all of the units I service specify an operating temperature range of 165° to 195°"

&

"Salt will begin to precipitate out of seawater at approximately 148° F, forming deposits on engine cooling passages, which ultimately will lead to poor water circulation and overheating. Thus, nearly all raw-water-cooled gasoline and diesel marine engines have a 140° thermostat. As far as heat exchangers are concerned, I have never had occasion to find salt accumulation during disassembly. The reason for this is the raw water that leaves a heat exchanger is only heated by approximately 10° to 15° above the temperature of the water entering the heat exchanger (if it's too hot to hold your hand in the exhaust outlet, your engine is either overheating or on the verge of it). Therefore, the raw water should never be heated anywhere near its salt precipitation point as it passes through a heat exchanger."

[dave davis]

There sure has been lots of interesting talk about thermostats lately. so I checked the one on my 1988 vintage. All I could find is the thermostat said 14lbs and lots of other numbers that had nothing to do with temperature. I can't remember every changing the TS. My heat exchanger
runs about 160 with no apparent problem. Although, I have found more green/yellow over flow in my bilge lately. Yet the level seems OK for now. I filled the HX about ten years ago when I had my HX taken out and cleaned at a radiator shop.
Dave

[Ron Hill]

Dave : It sounds as though you need to add a coolant recovery system I like did to my 1988 (back in 1989).
BTW, the temperature of a thermostat is stamped on the edge in Centigrade.   

[Stu Jackson]

Dave

The reference link in the second post on this thread gives you the model numbers and temperatures, in both C and F for the thermostats, plus the phone number of the company in Livermore where we purchased our new stats for lots less than Sea Power.  Ron's right about the stampings, but they are incredibly hard to see which is why a friend gave me a great birthday gift last year - one of those huge magnifying glasses!