Slabmaster
Mercury Alarm
2008 Mercury 4 stroke 115
This a new to me boat that I have recently purchased. I have an engine alarm going off in one continuous tone about two minutes after getting on plane. It first did it and i researched it and figured it sounded like an overheating issue, so i installed a new impeller just for peace of mind. Problem still existed so I removed the thermostat and tried it again. Well I use the boat a couple of times without a hitch so i figured the thermostat was bad. Then yesterday had the same alarm again. So.... I am gonna stick a new water temp sensor in this thing tomorrow and see how it acts then.
Now I know this thing has OBD but without a tool that isnt much good. There is a Crappie Tourney this weekend so i was gonna try and fix it myself before getting it in line at a garage.
Have any of you guys had any trouble out of these sensors? On the alarm symptoms from Mercury it lists this as a possible cause for the alarm.
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Crappie.com 2K Star General
Sand in the system might do that. The longer the water flows the more that gets moved to where it blocks flow. Try flushing the engine.
Temp sensor can be easily tested with an ohmmeter. Should be about 750 Ohms at room temperature and drop down to about 200 Ohms at 150 degrees.
Slabmaster
Will running it with the garden hose hooked up accomplish that?
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Crappie.com 2K Star General
Don't even need to power it up. Just measure across the wires and see if you get around 750. If not, it is probably suspect.Originally Posted by Snatch
Slabmaster
Thanks i will ck that
As far as flushing goes just do that with a garden hose?
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Crappie.com Legend
The dreaded mercury alarm!!! Hard to figure them out as they all have a similar sound and function.
Does it go in to "limp" mode when the alarm goes off? One thing to check on those motors. If memory serves me, there is a "pre-filter" screen in the water induction prior to the water hitting the impeller. Many boat mechanics with this model don't clean them. Pull the screens off your lower unit (where the water is sucked in). IF for any reason those are clogged, the system in these motors will sense low water pressure. The alarm you are more than likely getting is a low water pressure.
They also have a similar alarm for low oil and about 10 other things!
If memory serves me, I think that year of motor had a recall on all of the cylinder coils as well.
I have OCD "Obsessive Crappie Disorder"
Slabmaster
It takes it thirty seconds or so and then it reduces power so it may be going into limp mode. Would that be an intermittent problem though? It worked great for several trips where i drove it enough to sound the alarm but it didnt. Also it has only happened on the second drive cycle on a given trip. Never right off the trailer.
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Crappie.com Legend
I bet CatFan is right. Daddy's has done the same thing several times. Flushing should fix it.
Slabmaster
My local dealer had a sensor so I installed it and today for 2 drive cycles it worked great. The other sensor ohm tested at 10.03 at room temp. Im not sold that it is fixed yet but i will update this thread when it messes up again:/
Thanks for all the input!
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Slabmaster
Just to update this thread, the water temp sensor was the culprit. I have been 5 or 6 trips without a hitch! I am thoroughly enjoying my boat! Oh yeah, and the fishing has been great!
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