Optimax Oil Alarm

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
OptimaxM7
Posts: 4
Joined: Sun Jun 25, 2017 5:50 pm

Optimax Oil Alarm

Postby OptimaxM7 » Sun Jun 25, 2017 6:23 pm

Hi. I have a [1999 Mercury OptiMax] 225 DFI, serial number in 0G8xx, 365-hours runtime. The Smartcraft gauge oil sensor lights up 30 seconds after startup, with four beeps spaced every two minutes. If I disconnect one of the blue sensor wires, the alarm will not sound when restarting.

The remote tank is 3/4-FULL. I cleaned the slime off the cap dip tube screen. The under-cowling oil tank level is at the top.

I drained the [under-cowling oil] tank. The magnet donut is free sliding. The sensor measures open with donut at lower position. I filled the tank, and then the sensor measures 0.3-Ohms. Pushing the donut down one inch, the sensor measures open circuit. Releasing the donut, it floats up and I measure get 0.3-Ohms.

If I open the remote tank cap just after running, I can hear air hissing out. The brass check-valve-tee next to the [under-cowling] tank seems to work. I can suck through either 5/16-inch port, opening the small drain port poppet. There is no in-line oil filter leading to the [under-cowling] tank. The [under-cowling] tank cap and gasket look good with no leaks.

Is there any other oil sensor that would give the four-beep alarm?

If the oil pump were not rotating, would there be a continuous horn beep?

Or just the check engine light?

Thanks for any diagnostic help,
Mark

russellbailey
Posts: 99
Joined: Tue Nov 03, 2015 11:03 am

Re: Another Optimax oil alarm

Postby russellbailey » Sun Jun 25, 2017 10:13 pm

If the under-cowling oil tank is staying full, you could try jumpering that tank wiring connectors and seeing if that resolved the alarm. If so, the under-cowling oil tank sensor has failed.

I'd think you should measure zero resistance if the sensor worked right, or nearly zero - 0.3 sounds like a bit more than that.

I've replaced the under-cowling oil tanks on each of my 2006 Mercury 150 Optimax engines, one two years ago and one this year.
Last edited by russellbailey on Sun Jun 25, 2017 10:25 pm, edited 2 times in total.

jimh
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Location: Michigan, Lower Peninsula
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Re: Optimax Oil Alarm

Postby jimh » Sun Jun 25, 2017 10:22 pm

I don't understand what you mean by "onboard" tank. Do you mean the under-cowling oil tank? Or the external oil reservoir tank?

A resistance of 0.3-Ohms is what you often measure if you connect the probes of an Ohmmeter together. That is about as close to 0.000-Ohms as you can get with a meter using only two probes. To measure really low values of resistance, below 0.3-Ohms, you need to use a four-wire bridge-type Ohmmeter.

OptimaxM7
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Joined: Sun Jun 25, 2017 5:50 pm

Re: Optimax Oil Alarm

Postby OptimaxM7 » Sun Jun 25, 2017 10:36 pm

My 2.5-gallon external reservoir has no electrical sensor or piezo, just the twin oil tubing with blue stripe. The oil sensor (magnetic reed switch) on the cowling tank is reading "zero ohms" or shorted when the oil level is up. I did not subtract the DMM lead resistance.

I was reading up on the beep codes, and the other four-beep code is "water in fuel." The engine is idling smoothly, I just replaced the external water-fuel separator and under-cowling fuel filter, and I am running off of a one-gallon external tank with fresh gasoline at the moment.

jimh
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Location: Michigan, Lower Peninsula
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Re: Optimax Oil Alarm

Postby jimh » Sun Jun 25, 2017 11:07 pm

A sensor for water-in-fuel is often just a simple two-conductor probe that is inserted into a fuel filter so the contacts extend to the bottom of the filter bowl. Water has a different resistance than gasoline, and if water has separated from the gasoline and collected in the lower part of the bowl (due to its higher density) then the probe detects a change in resistance due to the water conductivity being different. If you disturb the probe contacts so they short together, you will set off a false alarm. Check that when you replaced one of the fuel-water separating filters or fuel filters that the fuel-in-water probes did not come into accidental contact.

OptimaxM7
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Joined: Sun Jun 25, 2017 5:50 pm

Re: Optimax Oil Alarm

Postby OptimaxM7 » Sun Jun 25, 2017 11:58 pm

The fuel filter came with a new sensor. I just tried unplugging that. Still got the four beeps and oil sensor light. I unplugged the oil tank sensor and put a 1-Kilohm resistor from the fuel filter sensor to ground. Restarted and got an immediate four beeps and the fuel sensor light came on.

Maybe I just unplug the oil tank sensor from the engine harness, and run a pair of wires up to my console, and use a relay (since the sensor is normally closed) to turn on another aural alert for a low oil tank alert. Then I can keep my Smartcraft gauge aural alert for any other alarms.

OptimaxM7
Posts: 4
Joined: Sun Jun 25, 2017 5:50 pm

Re: Optimax Oil Alarm

Postby OptimaxM7 » Mon Jun 26, 2017 12:12 am

I think I found something. I pulled the oil tank sensor and connected the wires to an ohmmeter. The sensor is about 2 in. long. When I run a pea-sized magnet along its length, the meter reads zero all along until midway. There is a deadband about 3/8 in. long in the center with no resistance. I bet thats right where the donut sits. I will get a new sensor and see what happens.

russellbailey
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Re: Optimax Oil Alarm

Postby russellbailey » Mon Jun 26, 2017 6:30 am

A more articulate description of the jumper is found at

http://continuouswave.com/ubb/Forum3/HTML/019894.html

Testing the tank and sensor can be tricky, so using a jumper avoids that - if the jumper fixes it, it is either the sensor or the tank. Replacing the tank fixes both.