Overheat warning or "you're too late!..." warning

[arriva2001]

Hi
I am wondering if any of you Force outboard owners have any thoughts on the overheat warning sensor.


I have a 1994 Force 150 that I've owned since it was new. I use it several times a year and always have it serviced. I've never had any problems with this engine until the last time it was serviced.


It was getting water in the gear case, so the dealer replaced the seals and while they were at it, replaced the impeller. They also REMOVED the thermostat--with a note on the receipt that the thermostat is not necessary unless in cold water (not sure I agree with this, but I went along with it since it was a mercury/Force service shop)..


I've only used the boat three times since this repair, and I've found that it works fine...I can cruise and pull a tube around all day, but then if I decide to slowdown fior a ride at or around idle speed, the overheat warning goes off.


I immediately shut it down and remove the cowl to air cool so I can start it again. Then after waiting about 10 mins, I can start and run again at full high speed with no issues.

3 questions


1. Is it legit to run without a thermostat, and could this actually be causing the overheat at idle? I plan to replace it myself ( the problem seems too much of a coincidence to ignore) but wondering if the repair shop doesn't know what they are talking about.


2. Other than replacing the impeller and checking for blockages is there anything else I should check or replace to troubleshoot overheat at idle?


3. Does anyone know at what temperature the overheat warning goes off vs. what temperature you actually do engine damage? I'm hoping by shutting down immediately when that sensor went off that I'm going to be ok. I'd hate to think that the warning sensor is more like a "oops you are too late..." sensor. I can't find anything around this online.


The overheat sensor has gone off exactly three times. The first two I thought were due to seaweed clogging intake. But now thinking its impeller. I always immediately decelerated and powered down....so hoping I didn't cause any damage... it's been a good motor for a lot of years (even though I hear a lot of gripes about the Force brand--this ones not caused me any headaches).

Any help would be appreciated!

 

[Jiggz]

The overheat sensor is set to go off at 160 degrees. Yes, it is OK to remove the thermostat especially if you are just running the motor in warm waters, . . . 70 degrees or higher.

No, you should still be OK if you shut down immediately as soon as you hear the high temp buzzer.

You are correct, the first thing to check is the impeller and also if the water tube is correctly connected. To check for blockage while the LU is off, you can connect a water hose to the water inlet tube and you should see water coming off the exhaust plenum.

Check the impeller and post your findings.

 

[jerryjerry05]

IF??? the factory engineers and design engineers made it WITH a thermostat??
Is it really necessary??
Yes it's needed.
The motor was designed to operate at a certain temp.
​You have a 130d thermo in there.
​The thermo switch is set to go off somewhere around 150-160d
Your motor was designed to run at 130d.
It gets better fuel economy when running at that temp.

Put it back.

 

[dingbat]

Not sure about Force, but a faulty poppet valve (broken spring) played havoc on my 175 hp Mercury outboard cooling system until I figured out the problem.

I rely on my water pressure gauge for cooling feedback.

I can see pressure rise and falls as the thermostats open and close. Provides instant feedback if something clogs the water intake.

Also a great tool to confirm impeller condition. When idle pressure drops below 3psi it's time to change the impeller

 

[Jiggz]

Just to be sure I am reading the initial problem correctly, the crux of the problem is overheating and not overcooling as indicated by the hi temp buzzer going off. And this is with the t-stat being removed.

 

[ondarvr]

Sometimes the thermostat is needed to restrict flow and keep water in the block, without some restriction the block won't fill correctly at low RPMs and can overheat.

​I don't know if this motor is plumbed like that though, but either way, it should have a thermostat.

 

[Jiggz]

No Title

I guess one way to find out is to re-install the t-stat and see if that will solve the problem. And I fully understand the function of the t-stat especially if operating in cold waters/weather. But in warmer water I do not believe having no t-stat will cause high temp on the engine. Of course, this is all conjecture.

 

[jerryjerry05]

Dingbat, the 94 150 doesn't have a relief valve.
He said he had a new impeller.
Jiggz, that pic is of an OLD 4cyl. with a relief valve.
​None of my manuals show a diagram of the 150 cooling.

Put it back in and take it for a ride.

 

[arriva2001]

Thanks everyone for your responses. I have a new thermostat and impeller (just in case) on order and they will be in on Tuesday. I'm going to install the thermostat first to see if that addresses it. I'll post my results! I'm also considering buying an aftermarket water pressure gauge or rigging up a "tell-tale" stream. I ordered a temperature gauge and sending unit as well. Any opinions on which is the better way to monitor for good water pump functionality? This overheat situation has me spooked!

 

[pnwboat]

It's probably personal preference as to how you want to monitor the water cooling. When I first set up my motor I had no idea as to which was better so I installed both a water pressure and water temperature gauge.

One problem I encountered with the temp. gauge was that the motor ran at around 130? - 140?F under normal conditions. Most automotive type water temperature gauges start out at about 100?F-120?F and go up to 260?F. When the motor warmed up, the needle on the gauge barely moved. I found a gauge that started out a 60?F and went up to 200?F. It worked much better. The 130?-140? temp. reading put the needle on the gauge right about half-way through the range of the gauge. You can see the motor warm up to the normal operating temp. The other gauge was pretty much useless.

If I had to do it over again, a Water Pressure gauge is probably good enough, but it's your choice as to how you want to do it.

 

[Jiggz]

I went with the water pressure gauge 0-30 PSI. Normal cruising at 2/3 throttle it reads around ~10 psi. At wot around 12~15 psi. However, there is also a setback on this setup especially for me boating in seawater. The sensing line is a 1/8" black hose and tends to clog up with salt build up. Hence, I have to flush it with fresh water before putting the boat on layup for the winter or after each season. If you operate only in freshwater, I guess it'll be a perfect setup.

 

[jerryjerry05]

One thing I noticed about almost ALL outboards and their alarm systems.
IF?? it gets hot enough to make the buzzer go off, the buzzer isn't loud enough to be heard over the noise of the engine.
My neighbors 200 2005 Yam. the buzzer is in the console and can't be heard unless the console door is open.
​A car or motorcycle horn works great.

 

[dingbat]

However, there is also a setback on this setup especially for me boating in seawater. The sensing line is a 1/8" black hose and tends to clog up with salt build up. Hence, I have to flush it with fresh water before putting the boat on layup for the winter or after each season.

never heard of such a thing. Three boats, 25 years, never once clogged

 

[arriva2001]

JerryJerry05, I agree. The warning sensor is not very loud on mine either. It's annoying for sure, but not very loud, considering all of the wind noise and engine noise when crusing... However, luckily, mine has clearly started going off when I'm putzing around at very low speeds, so I definitely hear it. It's not like I'm slowing down and finding out it has been going off for awhile....it very clearly starts after a few minutes of idling around very slow.

I'm hoping replacing the thermostat will fix the issue by ensuring the cool water fills the block and stays in long enough to cool it.. I had not thought that might be an issue, but it sounds plausible to me.

My plan tomorrow (if the part is in) is I'm planning to replace the thermostat, and run the engine at idle in my driveway in a big bucket of lukewarm water and monitor it.

If the alarm goes off, or temp goes up...then I'm going to need to pull the lower unit to see if something is wrong with the new impeller or something is plugged up or not hooked up correctly.

 

[Jiggz]

Just to settle the discussion once and for all, stick with your plans on just replacing the t-stat. Thereafter test it on the driveway with muffs or even better on the lake or body of water. If the buzzer doesn't come one, then maybe the t-stat is critical in maintaining a cool engine. Personally though, I have serious doubts that a t-stat will keep a cooler engine compare to one that doesn't have one installed.

 

[jerryjerry05]

It's also in there to restrict/direct the flow to other areas of the motor.

Did you get the old parts when you got the boat back?
Compare the impeller to the old.
​And yes please post the results of you "after" tests

 

[arriva2001]

I'm sorry, I did not receive the old parts back, so couldn't compare impellers.

Hey, I need a little help here. Any idea which way the thermostat goes in? Also, there is a long spring inside the thermostat cover. Not sure how to put this back together since it was missing the thermostat to begin with. Also I'm wondering if there are any other pieces that might have been removed by the mechanic. Does anyone know how to put this together properly or better yet have a diagram of the 150 force for me to refer to? I couldnt find one online, and my clymer manual doesn't even mention a thermostat!!!

 

[arriva2001]

Never mind on my last question. I did find a diagram in the Clymer manual. The reason I wasn't seeing it was because they only show the four cylinder powerhead, and there is a note that says "the five cylinder model is just the same as the four cylinder, with one extra cylinder added to the middle..." So I was able to figure out which way it went in. It's getting too dark in my neighborhood, so tomorrow I'll give it the idle speed test and see if this resolved things. Fingers crossed.....

 

[jerryjerry05]

F664914 seal
F719902 spacer
therom
spring
​gasket
cover
That's the parts you need and the order they go in.

​Both parts#'s are still available.

 

[arriva2001]

....and the results are: the thermostat fixed the problem! I installed the thermostat, took it out to the lake this weekend, and NO overheat problem whatsoever! I'll save the water pump and gaskets for the fall when I winterize. Also I have a water pressure gauge on the way, and will install it when it arrives so I can keep an eye on the situation. I have a digital thermometer, and I pointed it at the engine while idling for awhile, and it didn't get any warmer than around 133F.

I was going to install a temperature gauge as well...but when the sending unit came in the mail, I can't figure out where it mounts on the motor. It's about 2 inches long, so either I got the wrong one, or I just can't find the mounting spot. Hopefully the water pressure gauge alone will be enough!

thanks everyone for all of your help/advice!

Adam