hotter thermostat

[backdraft]

I have a 115 merc 4 stroke that is running a little cold. The thermostat opens at 122 and is totally open at 144, well within spec. It doesnt close until 114, which is too cold. No wonder these motors can get moisture in the oil. I fish is cold conditions ( 20 degrees)and the motor never does get very hot. (I use a infrared laser to measure temps). I was wondering if there is a thermostat that fits that bumps it up to 150 to 160. I realize the poppet valve takes over at higher rpms. Thanks for any advice. nevjb

 

[Silvertip]

Re: hotter thermostat

While what I'm about to suggest would very likely void any warranty you have, there is a possible solution to your dilema. Go to an auto store with your existing thermostat. 160 degree stats are available but not specifically for your engine (at least that I'm aware of). Check one for a 1992 Chev 4.3 V6 Astro or GMC Safari van. These are relatively small diameter units and perhaps you can grind the flange down sufficiently to fit the engine. Let us know if it works out.

 

[rodbolt]

Re: hotter thermostat

check all the tech bullitens from yamaha on the F115 and from merc on the F115, your 115 fourstroke merc is a yamaha with a black dress on. Yamaha has a hotter T-stat I believe.

 

[jimmbo]

Re: hotter thermostat

Stat temps are low because at temps above 140F disolved minerals in the water undesolve and deposit themselves in the cooling passages. In a closed cooling system like in an auto this only happens anytime fresh(new) water is added to the system. In a marine engine with raw water cooling it happens on a continous basis. Eventually the cooling passages will look like they were filled with cement.

 

[timmathis]

Re: hotter thermostat

Like said above. You mat can alter an automotive one to fit if you want to. I would stay in the 150-160 degrees range. Tim

 

[rodbolt]

Re: hotter thermostat

I know what they all say about scale and minerals above 140*F, however I will tell you that below 160* EFI fourstrokes make oil and I dont care who made it.<br /> its just a fact of life.the F200 and 225 yammies will run about 180 at planing speeds even though the tstats are set at 140. its just another fact of life. its also why some of the guys that like to troll for 4-5 hours have a few issues.<br /> I have watched the block temp go below 100*F after 2 hours of idle speed. its also why honda is playing with a dual tstat setup. one for cylhead and one for the block.

 

[Texasmark]

Re: hotter thermostat

So guys, did the EPA sell us a bucket of worms on this 4 stroke thing to clean up outboard motor emissions?<br /><br />Didn't know Yame'ha made Merc's. Merc must be scrambling for their own design. If they don't make their own powerheads, how can they compete in the marketplace?<br /><br />Hear you on the scale. I go thru a hot water heater every 7 years, regardless of how fancy it is and how much I pay for it. We are alkali here on deep wells here and the sacrificial anode just dissolves.....then your tank is dead meat.<br /><br />Temp is set to normal (140) and I flush them out every 6 months or so.<br /><br />Think I'll hang on to my '02 2 stroke with the thermostat removed, like the old days......so it can't stick and ruin a 3rd engine.<br /><br />Mark

 

[walleyehed]

Re: hotter thermostat

Mark, are you "really" running a 2-stroke with no Tstat???

 

[backdraft]

Re: hotter thermostat

Thanks to all. I will look into the 4.3 V6 thermostat. Mercury told me they didn't have a 142 to 150. I tried NAPA , got one and it fell right into the hole. Had to fish it out. First I will hit the Yamaha dealer then to Napa to see if I can talk them into going through the boxes for a match. Went fishing yesterday and the water was 42 degrees. Motor gauge barely got off the peg. It's a 60 to 200 degree gauge. Thanks again, I will let you know what I find. nevjb

 

[backdraft]

Re: hotter thermostat

Thermostat from V6 will not work I found. Did find that Yamaha does have a 144 degree thermostat that works . One is now on order from Yamaha. Pricey $35, Thanks nevjb

 

[Texasmark]

Re: hotter thermostat

Hey Walleyehead,<br /><br />Whadda you mean really? Health yes. the OB industry only did it for a hundred years (no stat). Why the current hooplah......EPA regs, but of course, grin.<br /><br />After 2 for 2 stuck therms on OB engines, one cost me a $1000 overhaul and 2 I caught early, I don't need one. At least with water going thru I'll take my chances with "carboning up". I never blew a powerhead on a non-statted engine.<br /><br />Besides, I don't know what I'm doing different, but I never had to decarbon any 2 cyle engine in my life. Will give you that in the days of leaded fuel there was some crud on the piston crown, but none since. And I run the surface gap plugs in my Mercs for years without having to change them. Matter of fact, I never do.<br />Maybe it's the Texas water. Grin.<br /><br />Later,<br /><br />Mark

 

[rodbolt]

Re: hotter thermostat

texas mark<br /> by removing the t-stats you have eliminated the water pressure control. that in itself can lead to hotspots. <br /> but on a properly maintained motor I have never seen a stuck Tstat nor a bad water pump and I tend to see a lot of motors.