What temp thermostat?

[Tony]

I'm switching the cooling system on my 302 back to a traditional thermostat setup. What temp should the t-stat be?

[Sam]

I'm think you have two choices either 140 or 160 degrees.

Sam

[MOP]

162 used to be the stock one for OMC.

[BigGrizzly]

use a 160 on a raw water system and 180 on a closed cooling system unless it is biown than a 170 t-sat. The reason is 140 is too cold for any system. a raw water system doesn't like hot exhausr because salts christalize in the exhausts manifolds. This not only applies to sea salts but fresh water salts and calcium depsits. This problem occures down here on Lale Lanier. It is especilly a problem on PWCs as they have a hot exhaust.

<small>[ March 30, 2003, 03:09 AM: Message edited by: BigGrizzly ]</small>

[Tony]

Thanks Randy and others for the replies. Looks like 160 it is!

[clayman]

I was running this weekend with the Boys (& Girls) on Lake Dora, and both times through the Dora Canal I began to run hot. I was runnning the 143 degree mercruiser recommended thermostat which ususaly has the boat running at about 160 degrees. half way back I stopped to make sure it was getting water, and the drive pump was pumping plenty, so I pulled the thermostat out, and made it back the ramp. It was then running about 130-135 without the themostat, but I figured it was better than 200-220 This problem has plaged me ever since I got this thing. any suggestions. Also, it always runs great temps here at our home lake, but has run hot almost everytime we hit bigger water with the long idle times through no wake zones.

[clayman]

I am running stainless marine exhaust with only 40 hours on them now, so I wouldn't think they are blocked, plus water is flowing nice out of the exhaust.

[MOP]

Have you checked the risers? May be the cause, you get a little more water through with the stat out. That may have helped you get back.

<small>[ March 31, 2003, 10:35 PM: Message edited by: M.O.P. ]</small>

[BigGrizzly]

Maybe you have a bad t-stat and a bad impeller in the lowerubit- You have the old 120 or Alpha don't you. Do you have a rew waterpump too.

[BUIZILLA]

Clayman, funny you bring this up...

When I was following you back thru the canals, I noticed your right exhaust had noticeably LESS water output than the left side did, Maybe half as much volume. When we got back to the beach and you and I were talking, I studied your engine/plumbing and I could see no reason for it, so I didn't say anything at that time.

Just a thought..

J

<small>[ April 01, 2003, 07:02 AM: Message edited by: BUIZILLA ]</small>

[MOP]

I know most people think the S/S will give you no trouble, this is true to a point. But I have seen them stuff up easier, I think the round holes not being as big as the cast type riser slots do catch more stuff. Even in fresh water you will get a little deterioation in the cast iron, just a few holes stopped up will slow the flow but can still look good. Why not try putting a 5 gallon bucket under each outlet run it on a flushete and see if the both fill about the same, they should be very close, if one side is a quart or two off I would pull the riser and check the holes.

[clayman]

That sounds good. I am going to pick up a new thermostat and the little brass ring that holds it in place on thursday, then I will try the bucket thing and check all my plumbing etc. Dose anyone run a sea strainer? I was thinking maybe I am sucking up seaweed or something and clogging it up ? Also, the impeller on the drive was replaced last summer (40 hours) is it time to replace already?
Jim
http://www.donzi.net/photos/jspiroff_dora_canal.jpg

<small>[ April 01, 2003, 10:04 AM: Message edited by: clayman ]</small>

[clayman]

Ok,I put in a new 140 thermostat, and ran the boat yesterday, it ran good for a while then jumped up again to 210. I ran it today on the hose for almost 30 minutes, at different rpms, and it stayed right at 160-170. I also had buckets to collect the water out of the exhaust (which doesn't work to well) and they seemed to flow the same. So I put it back in the water and ran it for about 2 hours through-out the day, and it ran great. So, the mystery continues.
Jim

<small>[ April 05, 2003, 10:31 PM: Message edited by: clayman ]</small>

[Cuda]

I'm betting on the impeller.

[KMLFAMILY]

Isn"t it at low speed you are primarly receiving flow from the drive impellar? Then as speed increase"s the engine pump volume takes over. 40 hrs. can be irrelvant if you have sucked up sand etc.or run dry.Also,do you have a transom flush by any chance? If so the internal plunger can hang-up causing a partial blockage.
Only trying to give you more ideas.

[Last Tango]

My 2001 C18 with MX6.2MPI is also equipped with EMI Thunder headers and risers. I also have a sea strainer kit because the B1 drive has low water pick-ups. Last year through the Dora Canal I still didn't pick up anything despite the very low water then. The strainer does pick up lots of stuff and is very easy to clean. I strongly recommend it for our vegatation and mud bottoms here in Florida.
No over heating problem, but the temp gauge stays pretty much in the 160 to 175 range.
I have also noticed that I "appear" to flow more water from the starboard side than the port when running the motor at around 1500 to 2000 RPM on the trailer with the "nose fob" and hose. I have many pictures of my boat running at higher speeds and the Corsa tips seem to be pushing the same amount of water, then.
I also notice that the upper unit of the drive get warm very quickly when I run the motor on the trailer. Is THIS normal? If the boat is not in gear, why would the upper unit heat up? In the water, I have a Halo drive shower to keep the upper unit cooler. Even at idle speed the upper unit is exposed above the water.
Mark (Supreme SEADOG)

[Stix Magill]

Replace the impeller just in case. If you have replaced it in the last year, it is probably fine.

My 350 mag has no thermostat at all. The previous owner said it ran best without it and my boat mechanic said it was fine to run without it. I didn't argue, but I am beginning to doubt this. After all, it is factory.....

Am I making a mistake to run without a thermostat?

Scott Smith

[MOP]

Being an old wrench I am a firm believer in using the right stat.

[Stix Magill]

MOP,
What would be the right stat? I asked my mechanic to install one, and he said something was missing... maybe a thermostat bracket? What could it have been that was missing? He said he could order it, but didn't seem concerned. As you can tell, I am not a engine guy...

Thanks,
Scott

[Walt. H.]

Hi Last Tango,Your stern drive unit still turn constantly as long as your engine is running, neutral or not. It's direct drive until you get to the gearing in the lower unit. That is where the shaft disengagement takes place for F-N-Rev. So yes it will warm up from the normal friction of the rotating gears warming your gear lube. The next question was= Missing part besides the thermostat.Stix's, Mostly likely might be the "brass sleeve" that sit's on top of the thermostat and holds it in place.Its the only thing that comes to my mind that could be left out and still be able to operate your engine. I hope this tid bit is of some help to you both. Walt.....

<small>[ April 07, 2003, 01:00 AM: Message edited by: Walt. H. ]</small>

[MOP]

Hi 160 for raw water, it is common on Mercs to get uneven flow to the risers at low speed if the regulator balls are shot. If you pull the riser hoses off at the thermostat housing you should find there is a ball on each side with a rod and a couple of springs, they control the flow at low speed, at high speed they compress the springs allowing full flow, hence one side getting hotter than the other at low speed. The balls wear after awhile and do not regulate the flow correctly at low speed anymore, if you take it apart and turn the balls around, they should seat better. when you take it apart measure the distance between the retainer nuts and put it back together at the same length. I tried to find a diagram but don't have one handy. Also if the prior owner removed the thermostat he may also have removed the ball assy. Though not critical I have seen people melt a hose when they wear bad. Merc out drive do get pretty warm on a flushette, I would not worry about it till you notice white residue, then you know its getting to hot. Contrary to what most people believe the drive pump supplies its highest pressure in relation to RPM at low RPM. Way back in tech school we hooked up pressure on the out hoses and vacuum gauges on the intake. We found that over about 3k all the readings dropped a little not a bunch. The instructor said the rubber impeller at speed did not contact the housing which caused it to loose some pressure. Even though I saw this test with my own eyes I still find it hard to believe. To this day I use both vacuum and pressure gauges in the water circuits when trouble shooting. You will pick up a bad riser in a heart beat or see that pump pressure is low. If you check your stuff when new and log the readings it only take a few minutes to hook up the gauges and recheck stuff. A tip use real long feeder hoses to the gauges off the tees that will keep the water out of the gauges, once they get wet inside they die!

[BigGrizzly]

There was an artical put out by GM on engine wear running a 140 t-stats up to 190. it clearly showes the wear increases dramitically below 160. This is one reason to put the t-stat back in. Any one telling you it runs better without any t-stat or restrictor is full crap. Unless of course the engine is broken to begin with. If your jetting is too fat, cold could be good because its like it is running on choke.

[Walt. H.]

Here is the other side or maybe now the third side. If your running raw water cooling in sea (salt) water the 160deg thermostat or above will cause the salt to crystallize and glog in your water passages do to heat.140* makes a big difference.I was running the 160* myself in fresh water and the shop where I get my parts from and borrow there speciality tools from still suggested to stay with the 140*! If you run high speed most of the time go by your engine oil temperature.You don't want that to thin out on you during high speed runs, that is where more wear will take place. I wanted to use the 160* thinking my performance and fuel mileage would be better.But i was told not so, 160 or higher is ok for a slow cruiser type boats. But not for a "Hot rod" to stick with a 140*thermo, and your engine oil temp will still be up close to 190-205 deg. I'm open for some good tech support here because i'm sort of caught in the middle agreeing with both theories.I do totally agree with the salt issue. I'm referring if the use is in raw fresh water cooling systems.I guess this may become a debate between "water temp" Vs "engine oil temp". I know there are plenty of "opinions" I've got my own too, What we need are "technical facts" Whats your inpute? Thanks :confused: :confused:

<small>[ April 08, 2003, 02:17 AM: Message edited by: Walt. H. ]</small>

[BigGrizzly]

Walt, we discussed the cristalization before in several other posts. Here are the facts. Merc and PCM now use 160 T-Stat because, in a water pump system or a crossover system with a bypass, the water is mixed with cold raw water before the exhaust. In my boat ,before the closed cooling system, my engine ran at 160 approx. but the exhaust was at 130-135. Exhaust is where the real problem is. In the block the water moves fast enough to actually prevent it. After talking with Thermo engineers from both Sen-Dur and one from Merc, That they wouls never use 140's agin. The newer Merc system with 4 hoes, from the water outlet, is designed to furthur reduce the outlet water temperature. In 1967 was the last time our 16 saw a 140 t-stat, I know because we still own it.

[Rootsy]

MOP,

merc no longer uses the spring loaded balls in the thermostat housing... i didn't know they had changed this until i started working on newer stuff quite a bit a few years back... i do not know exactly when they discontinued the use of them. Maybe when they did the change to the GEN II sterndrive about 1991 or so... On 80's and very early 90's merc motors i do know they still used them, ive had too many apart to know otherwise... and you are correct with the balls wearing a small flat in them where they contact the water outlets... then they get stuck. if you have ever gotten your motor really hot from loosing water supply you need to check them because i HAVE seen them bond to the water outlet and become stuck or in the worse case scenarios, melt and cause further headaches after a new impeller was installed...

i have to go with randy on the thermostat subject.. warmer is better but the reason you can't really go to a 180 or 190 in a raw water cooled motor is exhaust outlet temperature... So in this case run as warm as you can.. which would be a 160 or so... motors are more efficient when they are warmer... if this was not the case then every automotive manufacturer out there would run em as cold as possible.. but as we all see the trend has become to run em as warm as possible without burning em down... this aids atomization of the fuel and combustion efficiency, reduces friction and aids lubricity as well as burning off moisture and deposits. mercury marine and every automotive manufacturer out there knows exactly what they are doing.. nothing is done just for the heck of it...

<small>[ April 08, 2003, 08:33 AM: Message edited by: Rootsy ]</small>

[Walt. H.]

Hey! Big Grizzly & J. Rootsy,Thanks! Sounds good to me. When it comes time to put the thermostat back in.It will be the 160*. Currently everything is out, when I winterize the engine running with antifreeze mixture. I first remove the thermostat to insure everything gets circulated immediately with the green stuff. Limited run time with five gal mix and fogging it too at the same time. Also I too experience the same problem last season with a stuck left ball. eek! That didn't sound right? Maybe I should re-phrase that,Nah!!! It was but I didn't turn it around or replace it I re-dressed with a small file and polished it smooth with some 320,400,600 wet & dry paper. A real quickie job just a few wipes with each. Anyway, thanks guys, Walt..... Ps. The automotive industry runs 195 and higher thermostat's not for performance or longevity of the engine. On the contrary! Its to help meet governmental emission standards :mad: . Prior to that pre-70 it was the 180deg for stock and we used to put in a 160* for summer time use.Re-install the 180* for the heat in the winter.

<small>[ April 09, 2003, 01:46 AM: Message edited by: Walt. H. ]</small>

[BigGrizzly]

Actualy Walt I work for an automotive manufacturer. We did raise the thermostat to 190 to increase performance and engine Longevity. When you have a more complete combustion the more calories you make and the more horsepower per pound of fuel is made . In 1975 GM produced a graph on engine ware that shows it increases below 160. Todays optimum operating oil temp is between 190 and 210. With colder running temperatures you have a tendancy to get oil dilution. In the old days fuel would pass the rings and mix with the oil than would find its way back to the rings and carbon up and also cause sludg. Moat of this was due to too cold engine temperatures the rest was due to leaded fuels. Ther are atleast 50 SAE papers on the subject. Sludg is a thing of the past,in engines of to day. I learned the hard way and now I'm a real beleiver.

[Walt. H.]

Hi Grizz, Ah! Good old wonderful leaded high octane fuel. Ok. Question=Wasn't the higher temp for leaner fuel mixture burn to lower exh emissions? I know we are getting away from the boat topic of engine temps.But I'm enjoying this reminiscing stuff, and oil sludge was aliminated with the use of detergent oils, better engine clearances to stop blow-by etc?

[BillG]

Let me throw another log on the fire. I have a theory about raw water cooling. Having run the same engine for 20+ years before it rusted through one head. It never ran over 80 degrees, when I tore it down there was no cylinder ridge, no sludge, and no wear that you would call not normal. My theory is that the oil keeps the internal engine parts at what we would call normal temps because there is no air flowing over the oil pan to cool it as in a car. The valve covers always were to hot to touch so the engine did not run cold internally. Just a thought....BillG

[BigGrizzly]

Walt off the topic just once. You are close. Remember at the time the plug gaps went to .060. They did this to burn a leaner mixture, which caused more combustion chamber heat in low compression engines. Sombody discovered that higher oil temps acrually cause less wear. Two companies sent out information about this one was GM the other was Continental. They than ran a 3 stage cat which got real hot. This was a bandade to satisfy the powers to be. Mean while oils are getting better and better. The old High Detergent oils were no longer produced after the 1960. The oil companies kept the HD designation to satisfy the consumer, who assumed it ment high detergent, but in fact it ment heavy duty. Now enters the oil grading MS, (motor severe) now they went to SA,SD etc. I could go on for hours. I learned this because I was doing oil testing for my company and went to most of the makers for information for our testing. I discovered an interesting fact. The worst oil that any maker has is their 10w/40. In 1984 GM sent out a bulletin that stated they would void any warrant on a unit that used 10w/40. It is true that they have gone down to 5w/30 to increase their fleet average mpg.

BillG, could this lack of wear be due to more frequent oil changes per hours of use. I use my boat almost every weekend usually from April to October which is only about 160 hours per year average over the past 3 years. I change my oil twice a season. My car I put (according to the hour meter)14 hours a week which comes to over 700 hours a year and this gives about 350 hours between oil changes. Another strange thing I noticed is (generally speaking) people warm up their boats but rarely their cars except to get the heater going before going work in cold weather.

[BillG]

Griz,
I use my boat at least 4 or 5 days per week. I think the hours would come out to about 250-300 per year. I change oil once per season. I can't explain the reason it was not worn much. I have always used Quaker State 10-40. Don't the auto makers also use 5-30 to cut down on start-up wear in cold weather? It lets you build oil pressure more quickly.
Just a thought.
Bill G

[thriller]

bump..good reading

[joseph m. hahnl]

I'm betting on the impeller.




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