Alarm-gctid382880

[Guest]

The Alarm on my 1998 2355 goes off sporadically all the time. I disconnected the wires from the gear lub reservoir so that not the problem. The temp is 175 and steady and the oil pressure is 42 at idle and also steady.Does the alarm system have a relay and could this be bad? Where can I find a wiring diagram so I can see what all brings on the alarm?

[Guest]

I don't know the engine type you have, however if its carbed mercruiser likely problem is the oil pressure switch. Check the wires for corrosion. On a mercruiser there a pressure sender that allows pressure readout on the gauge, and the pressure switch that trips the alarm if the oil pressure is critically low. Chances are the oil pressure switch is busted or something is wrong with the wiring.

[Guest]

Sorry My engine is a 5.0 chevy that is carbed. Can you tell where the oil switch is located?

[Guest]

seasam wrote:
Sorry My engine is a 5.0 chevy that is carbed. Can you tell where the oil switch is located?

On my 2005 5.0 Mercruiser it is located next to the oil pressure sender in the same general area as the oil filter. It has one wire coming out of it that goes in to a harness. When you locate it, it is good idea to disconnect the wire and simply try cleaning the contacts first. If you ground that wire it will act as if switch is engaged so it is easy way to check if a faulty oil pressure switch is causing your alarm issue. If you can run the engine with the grounded switch wire and no alarm, you need to replace the switch. Its about $25 and very easy to do.Here is what it looks like:

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[Guest]

Thanks Grindkore So with the wire to the switch grounded, no alarm should sound? Does 42 lbs of oil pressure at idle sound right? The boat is new to me and I don't know its history. If this doesn't work I will look at the temp switch next. Do you know if it works the same way ...grounding the wire will not sound the alarm? What else will sound the alarm?

[Guest]

These wiring schematics are available on the web, try the mercruiser site first. These various alarm switches are simple open & close type. Think of a light switch) They are referred to as normally open or normally closed. This would refer to what position the switch would normally be in as it were laying on the counter. IE no pressure or temprature applied to it.

So the basic alarm system is set up as follows. First, there are usually 2 oil switches. The first is used to allow power to the electric fuel pump, if equipped. (note that these can fail, your engine will start & run for abour 15-30 ceconds then die, if you restart, it will do the same again, over & over. This will leave you dead in the water. Simply disconnect the two wires & join them together to by pass this switch & get home. ** be sure to replace this asap after you get back to port. It is there so the fuel pump shuts off if your engine stalls) Your Low oil pressure alarm is normally closed (meaning there is continuity when the pressure is below the switch setting usually about 5-10 lbs) When the pressure drops, the switch closes & sets off the alarm. When you turn on the key to start the engine, the alarm should sound to indicate no oil pressure, then as you crank & start up, the pressure builds & passes the switch setting (5-10 lbs) & the switch opens & the alarm stops. Note that the oil switches are located on theport side, just ahead of the oil filter. The temp alarm is normally open, no continuity, when the temp reaches the switch setting (usually 195-205) the switch closes & sounds the alarm. Note that this switch is seperate from the gauge sender. The drive oil sensor switch is normally closed, when there is adequate drive oil the switch is open, when the oil level drops, the switch closes & sounds the alarm.

The temp gauge is on a seperate circuit from the alarms. It works on resistance. as the temp rises the resistance changes & the gauge reads higher. The gauge it self, usually works or not. The sender is usally the culprit for incorrect readings. Go to your auto supply & get yourself an infared digital thermometer (a heat gun or, temp gun) you can use this to check the surface temp of various things in the home or boat manifolds, water temp, alternator, bearings, tensioner, wheel bearings, brakes. girlfriend etc. 30-40 $$. simply point it at the spot (usually next to the sensor) & see if the readings agree. Check ALL of the connections for good contact, clean the terminals & apply a wipe of Dielectric grease (or even Vaseline) on the terminals. Be sure you also clean & check all the ground wires as well, most electrical problems are related to a poor ground.

[itsabowtime2]

That pressure seems "high" for idle. As others have said, check your connections to see if they are loose or need a good cleaning. Use some di-electric greese on them. Also, check temps with a thermal temp gun...gauges can be inaccurate.

[Guest]

itsabowtime2 wrote:
That pressure seems "high" for idle. As others have said, check your connections to see if they are loose or need a good cleaning. Use some di-electric greese on them. Also, check temps with a thermal temp gun...gauges can be inaccurate.

42 Psi is normal at idle. I see 45psi idle and 75 psi at above 2K rpm. Using standard Quicksilver 25W-40 oil and mercruiser brand filter, once the oil warms up it becomes less viscous and usually lose 5 psi or so on the high end.

[Guest]

Thanks to all who posted. Turned out to be the temp switch. I disconnected it and no more alarm. Ordered a new one. While checking other wires I found that the wire on the alt. was burned off. Everyone said to check all connections and everyone is right!!! Again Thanks to all. With out this info I would have had to pay for repairs and wait 3 weeks because they are backed up.

[Guest]

Installed the new temp switch and still the alarm goes off sporadically. The temp gage is at 175 And though I don't have a heat gun the engine doesn't feel very hot .Any thoughts?