288 intermittent alarm
 

Having an issue with our 03 288 w/ 496 HO.
Alarm went off so checked gear lube. It was a little low. Added lube. No alarm.
Later that day alarm goes off again., gear lube was down a hair. Thought it was a gear lube leak.
Had it pressure tested by boat shop. No issue. Thought reservoir float was bad. Replaced reservoir.

Next time out alarm goes off. Check gear lube and it's full.
Start up no alarm. It happens again.
Notice temp gauge is slightly higher than normal. Normal is 190, it was a hair above that..
So replace sea water impeller.
Go out yesterday and alarm goes off again. So frustrated.
Temp is up so prettty sure it is the over heating alarm.
Shop owner said the closed system antifreeze never needs changed.
I just read in the general forum on 496 overheating saying the pink AF can get dark and metallic and will not do it's job after 7 years or so.

But all 496's are not the same so hoping for some insights on what the heck might be going on. I want to boat.
Advise please..

Somebody needs to do some testing, need to put a scanner on it. The solid alarm can be ECT, oil pressure. lube, low water pressure, and if a sensor looses ground. The most common failure is the water pressure sensor

Are you getting any power reduction from the ECM when the alarm goes off? My guess if your like most , soon as it goes off the throttle is pulled back

Thanks for your reply AllDodge.
I had not noticed a loss of power until yesterday before the alarm went off I did feel the loss of power. It seemed like I might have spun the prop. It was the first I had this since I stop at first sign of the alarm. After sitting it would cool down and no alarm for a while. Obviously it has gotten worse. I could cruise 5 to 10 miles at 3500 rpm no issue. Then next time I would cruise a few more miles and it goes off. Stop, raise hatch check things out, by then I guess it cooled enough so it would not go off when I started up and cruised a little more.

Did notice steam coming out of thru hull exhaust when running quiet with captains call.
Also found this:
Constant tone alarms are for:
1.) engine coolant temp overheat,
2.) low engine oil pressure,
3.) engine overspeed,
4.) exhaust manifold cooling temp overheat
5.) sea pump PSI low.

I do think I have an engine coolant overheat issue since sea pump was just replaced. Old sea pump did not show signs of wear, and was completely intact so no loose pieces to get stuck anywhere. But ...that is my uneducated guess.

Maybe use an IR temp gun to measure temp at the thermostat housing. The gauge may or may not be correct but in any case, the ECM uses another sensor on the thermostat to tell it if its overheating.

Assuming B1 and hope it wasn't a coupler

I hope not also. I 'think' it was due to the alarm. Fingers crossed.

Thanks. Will do.

Ran into this on my old Dominator. Would run cool enough at idle but as soon as the boat was planed out, it would start to warm up. Like Crown said, backflush. And, when you think you've done it enough, do it again.lol

You need a new shop/mechanic.... 5yrs/1k hrs on engine coolant whichever comes first. Right out of Merc 496 FSM.

190*+ is not normal operating temp for a 496. That is too hot. Stock they should be 160-180* range. At 190* + ECT temps you are probably close or tripping the EMCT sensors. These trip at 212*.

As said, backflush complete seawater side of cooling system. Pull heat exchanger endcaps, flush internally, replace endcap gaskets. Endcap gaskets deform and will block water flow. Also could possibly be the "Bravoitis" tube corroded.

A techmate/scantool scan will pinpoint exactly what fault is being thrown.

Backflush and if that does not do it check to see if the brass sea pump housing has grooves in the housing. Has it every had a new sea pump housing?

Thanks all. I've had this boat since 2014 . Never had closed cooling system before. It has run at 190 4 years now ....just having problem this year. I should have asked about 190 as a normal running temp years ago. Crap. Sure has me worried now. Will post update when I know more as to the fix.

I do not know if it has had a new sea pump housing. Will find out.

Need a IR temp gun to measure the thermostat housing. Gauges may or may not be accurate

Agreed on IR Temp gun but with steam coming out of the thru hull pipes I'm pretty sure gauge and alarms are working as intended. Thanks for your thoughts on this issue.

you can watch real temp with the scan tool. alot temp gauges at the dash are off with the readings.

Backflushing alone is not going to unrestrict cooling passages 100 fully. - alot of times you have pick out the blockage plus there is other forms of blockages in the cooling system. ie deformed gaskets, mineral deposits and aluminum oxide deposits especially in the cooling section of the cool fuel ( GEN 3 if applicable) also the check balls aka check valves cause cooling restrictions along with any kinked hoses.

You need describe the alarm, beeeeeeeeeeeeeeeep all the time

or beeeeeeep pause beeeeeeep pause

beeep beeep pause beeep beeep pause

the alarms all mean different things

It is so simple to rule out the gear oil bottle if that is your alarm - when the alarm is going off --- unplug the leads to the gear oil bottle - if alarm goes away then you found the problem, Just because the gear oil bottle is full of gear oil means nothing - the sensor / magnet pickup or float can be bad causing the alarm as well.

Mine are 2008 eight model HO with 400 hrs and just Sunday the port motor started the 2/3 second beep then pause then repeat beep. before shutting down i glanced at oil pressure and temp which were normal. we were at idle so water pressure was not really registering on the gauge. I had checked engine oil and drive lube the day before and checked engine oil and felt the risers after the alarm but no issues there. I failed to look at the drive lube bottle before taking it to the shop. I thought drive lube was a constant alarm??

Drive lube bottle horn is INTERMITTENT CONTINUOUS BEEPS. it is NOT a continuous horn. Those are more severe warning horns.

and again just because the bottle is full means nothing for producing a warning horn. Huge misconception by many.

is that what the warning sounds like for low drive lube or lube bottle senor? Or does that same alarm mean different things, I assume it will have stored a code?

bottle has the sensor in the bottom, it only has one alarm period.. You can set your own alarm off by pushing down the float all the way inside the bottle to test if it is working properly. Many boat owners drive lube sensor alarm do not work anyways because they never clean out the thick gel pudding of gear oil that has formed over the years .

Very easy to test the drive bottle alarm / sensor and the with just key on.

on scan tool it show under low drive lube strategy as a fault code

So I ll ask and I know as I am NOT asking to find out - so I will ask others --- what fault code number is this for pcm 555 ? Low drive lube strategy ??? Who will be the smart one here ?

fault 12

where did you come up with that fault 12 ? thats LOW OIL PRESSURE - motor oil ---- and that will set a guardian

I am going to stump the band here - or am I ??? PCM 555 - 496 low out drive lube warning is fault number what ???

Mine is a continuous beep. Ruled out gear lube by unplugging one of the leads. Seeing the temp gauge higher than normal and seeing steam come out of the thru transom exhaust when idling and after turning off points me to the overheat issue.

the solid horn non stop ruled out the drive lube bottle and like I said the solid non stop warning horn are more severve fault(s).

Would bet on ECT overheat and EMCT overheat are the mix here and they are both solid non stop warning horns. The heat exchanger needs complete clean out -- all new anti freeze totally --- all gaskets and grommets need to be changed for the heat exchanger and related parts to it.

The Impeller and housing is another issue on top of as it is always the norm for those 2 items. They are not just on the 496 either so I see the gen VII water pump fail all the time. Boating season almost a daily item for an issue.

Always post what warning horn(s) are going off because it will eliminate some of the dart throwing by the ones whom really know what they mean plus what goes on with PCM 555 and ECM 555. - Was it ever posted what warning horn it was going off ?

Thanks BUP.
The primary culprit was the heat exchanger. It had accumulated a good bit of trash. Plus the temp gauge is reading 12 degrees higher than the actual temp. Gauge now shows normal operating temp of 176. Minus 12 means I'm running about 164. Before cleaning the heat exchanger and replacing the antifreeze normal running them was 190, so in actuality I was running 178.

[QUOTE=BUP;4635794]you can watch real temp with the scan tool. alot temp gauges at the dash are off with the readings.

Could nt have spelled it out any better.

[QUOTE=BUP;4636003] the solid horn non stop ruled out the drive lube bottle and like I said the solid non stop warning horn are more severve fault(s).<br /><br />Would bet on ECT overheat and EMCT overheat are the mix here and they are both solid non stop warning horns. The heat exchanger needs complete clean out -- all new anti freeze totally --- all gaskets and grommets need to be changed for the heat exchanger and related parts to it.<br /><br />Post 22 ^^^^^^^^<br /><br /><br />Could nt have spelled this out any better as well.