Engine Temperature Warning Horn

[Bassinvan]

Hey guys, at what temperature should I get a warning horn from my 250 Pro XS?

I have a system monitor in the dash.

Ser.# 1B521097

Thanks Van

[Savage]

What temperature is your motor?
Is the motor currently alarming?

[Murph44]

My boat last year was a month old . My warning horn was going off.. took it back to the dealer , he plugged it it , ran the codes . Found that the cranking battery was not pulling enough amps for the oil pump to work at higher rpm.. horn would go off and turn down the rpms to save the motor.. changed the battery and no issue .good luck

[Bassinvan]

The boat is in the shop being checked out, I'm being told some temps that are "normal" I find hard to believe after running an Optimax for 14 years and a Pro XS for 2.

I'm referring to engine temp before the thermostats (130 degrees) open and the temp when the warning horn goes off.

I'd rather not quote the numbers I'm being told until I get some feedback from the members here.

Thanks Van

[Savage]

The motor will alarm if it doesn't come up to the proper temperature in a certain amount of time.
Alarm will sound if the compressor is overheating.
Alarm will sound if the motor is overheating.
Alarm will sound for a bunch of other reasons also.

Running temperatures will always vary.

Its best if you just explain what is happening with your motor!

[Bassinvan]

Ok guys I'm back, Savage here's the story behind the initial question.

My first three trips out this year were in January-February the lake water temperature was 40*, my starting routine once the boat is launched is to set my smartcraft gauge to water pressure, start the engine and visually confirm water coming out the tell tale, then check the gauge it usually shows 2.2 psi =/- (engine in neutral at idle).

Then I switch the gauge to engine temp and watch the temps climb, when the gauge shows 140* then the t'stats open and temps drop to 122-125.

At this point I put the engine in gear and idle away from the dock, once past the no wake zone I step on the gas and the boat planes off, engine temps drop to 118*.

That was the "normal" part.

Now the problem, after sitting in my garage for 3 weeks I head out for trip #4. I go thru the same start routine and get two key numbers quite different from trip #3. Water pressure doubles from 2.2 psi to 4.4 psi, I change the smartcaft over to engine temp and watch it climb past 140* all the way to 151* before the t'stats open and the temps drop to 122-125* (lake water temp still 40*).

Engine temp and psi still good while running on plane.

Trips 5&6 produced the same readings except engine start up temps increased to 157-159* before t'stats opened.

I have not heard any warning horns.

I've replaced the t'stats and the poppet valve, the water pump was replaced less than 6 months ago.

Everything else remains the same, I'm thinking I have a water passage partially blocked resulting in higher psi. No guess why engine temps changed so much and went so high before the stats (new 130*) opened.

Just to add a little more confusion, while riding up the lake one day with the smartcraft set for engine temp it changed itself to "trim", it's never done this before.

I checked my smartcraft gauge manual and found the "pop up trim" setting to be "on", but the trim setting has never been calibrated so the display has always shown "0.0"
so without the value ever changing why would the pop up trim decide after two years to "pop up"?

Could all of this stuff be an electrical problem?

Thanks for hanging in there and wading through all this.

Van, Lost in thought.

[Savage]

Do you have a good tell tale stream from the compressor cooling water? Has the compressor strainer been cleaned?

[Bassinvan]

Yes to both.

Van

[Savage]

Did you replace the thermostats with Genuine Mercury Marine thermostats?

[Bassinvan]

Yes, got them from Don.

[Bassinvan]

One of his techs water tested them, reported began to open at 119* fully open at 130*

[Savage]

Have a Dealer read each individual temperature sensor with a CDS.

[Bassinvan]

Hi all, I finally got in touch with the shop working on my boat and found out they're waiting on the new serpentine belt before any more diagnostic work. The service manager says the tech ran the boat(with the current belt, it's squeaking) and found the temps "within Mercury spec". The numbers he quoted to me were 157* before the t'stats(I installed new Mercury 130* t'stats previously) opened with a running temp of 175* before a warning horn sounds. These don't sound right to me.

I told him to check the engine temp sensors with their computer. We'll see..

They have no explanation for why the water pressure on initial startup doubled from 2.2 to 4.4 as shown on the smartcraft gauge. I told him to drop the lower unit and inspect the water pump, gaskets, and housing for damage, also check the water passages for obstructions.


When I was trying to fix this myself it felt it felt like I was pulling a wagon up a hill, now that a Mercury dealer has it I feel like I'm pushing the wagon up a hill.

Thanks Van

[Savage]

You should get print outs of the CDS testing.

[Bassinvan]

Thanks Savage, I'll relay that to the service manager.

Van

[jxb9723]

I'm interested in the results your mechanic gives you. I have the same exact problem for 5 years. It continues to run fine with no alarms. I just get an initial startup temp of 150-159 then it settles to 132. Prior to this issue it never got above 140. I've been told twice its fine but I still wonder.