Faulty sending/sensors?

[dmoccia]

How can I verify whether or not I have faulty alarm sensors? I have three on my 2005 Bayliner 185 Mercruser: oil pressure, temp, and gear oil level. My alarm goes off intermittently while driving the boat but temp (175deg) and oil pressure (around 40psi) are normal and my gear oil; reservoir is above the low fill mark.

 

[alldodge]

My guess is your running hot, you should be lower then 175*

What is your motor serial number and are you closed cool?

 

[poconojoe]

I'll follow...
My boat is basically the same, but it's a 2003.
I don't know which engine you have, but I have the 190 hp 4.3L Alpha 1 gen 2.

When was the last time you changed the impeller? How about the thermostat?

My temperature gauge reads a little under 175, but it's hard to trust those gauges. I should scrutinize it a bit more to give you an exact number.
The important thing in my mind is that it's steady. It has always read pretty much the same after an impeller and thermostat change a few years ago. So, change out the impeller and maybe your thermostat and see what the gauge reads. If you are satisfied it is truly running at the proper temperature, note where the gauge is. That's your benchmark. I almost ignore the numbers on the gauge. As long as the needle stays steady, I feel ok.

 

[Scott06]

How can I verify whether or not I have faulty alarm sensors? I have three on my 2005 Bayliner 185 Mercruser: oil pressure, temp, and gear oil level. My alarm goes off intermittently while driving the boat but temp (175deg) and oil pressure (around 40psi) are normal and my gear oil; reservoir is above the low fill mark.

use an IR gun to see how hot thermostat housing actually is , then unplug the temp switch see if it goes away. Just want to verify the temp is actually ok. if temp is ok and unplugging it doesnt make alarm go away unplug the lube bottle and separately the oil pressure alarm and see if it goes away.

you can test the pressure switch by heating it and seeing what temp it closes at

 

[Scott Danforth]

175 is running hot. Use an IR thermometer to verify

 

[poconojoe]

Adding to what previously I stated for reference.
I said my temp gauge usually reads a little under 175. Looking at it yesterday, I can estimate that it's reading around 160, which is great. The gauge increments are a bit strange, but that's what I figured.

So, as I suggested, start fresh by changing the impeller and thermostat to get a baseline on where your gauge reads.

 

[poconojoe]

IR thermometer is a great idea.
I gotta get one of those!
So many uses for one.
Exhaust, wheel bearing temperatures, etc...

 

[dmoccia]

I'll follow...
My boat is basically the same, but it's a 2003.
I don't know which engine you have, but I have the 190 hp 4.3L Alpha 1 gen 2.

When was the last time you changed the impeller? How about the thermostat?

My temperature gauge reads a little under 175, but it's hard to trust those gauges. I should scrutinize it a bit more to give you an exact number.
The important thing in my mind is that it's steady. It has always read pretty much the same after an impeller and thermostat change a few years ago. So, change out the impeller and maybe your thermostat and see what the gauge reads. If you are satisfied it is truly running at the proper temperature, note where the gauge is. That's your benchmark. I almost ignore the numbers on the gauge. As long as the needle stays steady, I feel ok.

 

[achris]

Adding to what previously I stated for reference.
I said my temp gauge usually reads a little under 175. Looking at it yesterday, I can estimate that it's reading around 160, which is great. The gauge increments are a bit strange, but that's what I figured.

You (and everyone else) needs to realise that the reading on a dash gauge is only an indication, not a calibrated accurate scientific instrument. It could easily be as much as 15 (or more) degrees out. Just like your dash tacho, it's not a precision instrument... It's designed for you to get an idea of where it is normally (not the actual reading, but the needle position), then if it's not 'normal', you know something is wrong...

Chris......
(I have no idea why they even bother to put the degrees on them. They didn't in the early days!)

 

[Earl Cordova]

There are actually a lot more than 3 sensors that are monitored by the ECM.
You either need to purchase a code reader or have a shop connect theirs.

 

[poconojoe]

You (and everyone else) needs to realise that the reading on a dash gauge is only an indication, not a calibrated accurate scientific instrument. It could easily be as much as 15 (or more) degrees out. Just like your dash tacho, it's not a precision instrument... It's designed for you to get an idea of where it is normally (not the actual reading, but the needle position), then if it's not 'normal', you know something is wrong...

Chris......
(I have no idea why they even bother to put the degrees on them. They didn't in the early days!)
View attachment 347795

That is exactly what I was trying to say Chris.
Maybe I didn't convey it clearly.

I only use the needle on the temp gauge as a reference. The numbers and the increments are pretty much useless. I did give a guesstimate that mine runs around 160.

After a new thermostat and impeller, I noted where the needle was and that's my baseline. As long as it doesn't go higher, I feel ok. I actually at one point thought about drawing a line with a sharpie where the needle sat, but it's easily recognizable at a glance.

We all know most of these gauges are grossly inaccurate, but at least a baseline gives you an idea that you are within an acceptable range.
And yes, that works if the gauge is sort of consistent, which you will determine by a constant glance.
You should be glancing at all your gauges anyway.

Cheers!