Mercury 496 Bravo 3 Alarm/Guardian

R

ROSARIO PUGLISI

Member
Oct 30, 2020
37
Boat Info
2008 SeaRay 270 SLX
Engines
Mercury 496 W/Bravo lll
I have a 08 Searay 270 SLX . 400hrs . problem I’m having is . Boat running no issues running up to as much as 3200rpms Guages are all reading fine oil/temp/water psi. Etc.. also all level are normal drive lube an oil etc.
so when I idol down to as low as 1000rpm oil pressure drops between 30&40psi and sets off alarm . I shift to neutral alarm shuts off an oil pressure stays at the 30. I then idol back up and now issues . Murphy’s law I had mechanic put computer on it an everything was fine . Both at idols and taking boat on bay test with computer hooked up an what do you think nothing happens no alarms . Does anyone have any ideas .
 
If it only happened once I would not be concerned. It happens, clear code and it doesn't repeat More common than you think. Cars, trucks motorcycles all the same.
 
It’s happened quite a few time But not all the time . Like today i made a 25 min run up to 3k rpms and when i idoled down it happened. Now on return trip i did the same exact thing ran it at steady 3k rpm and idoled down and it didn’t happen.
 
Need more info...What kind of alarm, steady, 2 beeps a minute, does it quit after a while? Will it go WOT?
 
scoflaw said:
Need more info...What kind of alarm, steady, 2 beeps a minute, does it quit after a while? Will it go WOT?
Click to expand...

It’s a steady beep for about 20 seconds . During that time it alarms as pressure is dropping exactly at 40psi and stays steady beep as it gets down to 30psi and then alarm shuts off.
 
I would tend to go to the oil press alarm switch. Pressure doesn't sound super low, but not high. Screw a mechanical oil press gauge in and see what it actually is. Boat gauge may be off.
 
Or disconnect the lead to the oil alarm switch and see if it still alarms. If not, you know what you need to fix.
 
When you say oil alarm switch do you mean this ?

B07462DC-37AC-47D0-B972-4BDAE71FBC5F.jpeg
Bill Curtis said:
Or disconnect the lead to the oil alarm switch and see if it still alarms. If not, you know what you need to fix.
Click to expand...
 
ROSARIO PUGLISI said:
When you say oil alarm switch do you mean this ?


I’m hearing multiple part names ,
Oil Pressure Switch
Oil Pressor Sensor
Oil Pressure Sender

I’m also told that the newer 496 Mercury have combined them and there is only a single Switch , no sensor and no sender.
Click to expand...
 
I would suspect the sensor. If it alarms at 40, it should alarm all the way down past 30. I have 2 496mags with Br 3s, my oil pressure runs at 53 on port and 51 on stbd running at 3250-3300.
I did have issues when coming off plain of my engine temps going up to 178-182 and got alarms. Especially when the bay water temps were in the high 80s as they are now. Replaced manifolds, impellors, 1 raw water pump, and ran a loop through the raw water system using barnacle buster. Problem solved. It alarmed with long alarm until the engine temp dropped to below 178. No faults. This would make sense as if you engines are getting hot when coming off plain as the cast iron absorbs the heat, the oil would get hotter and thinner and could cause the drop you are seeing. Just thinking outside the box and trying to give you a differential diagnosis to think about.
 
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