2005 Optimax 115hp alarm

[justmagic]

My local Merc mechanics are booked out for a month so I've been attempting to locate the cause of a constant sounding alarm (IE solid continuous beep) that puts the motor into guardian mode until revs are backed off.

HISTORY: About 6 months ago the alarm came on at certain throttle positions and would go away if I moved the throttle quickly up to planing speeds. Noticed the throttle itself was loose and rattled a bit in the had. Dismantled and tightened everything up and alarm went away.

Two weeks ago the alarm returned whilst offshore. Throttle still tight. Again a constant, single, solid continuous beep. Plenty of oil, plenty of pressure in the tell tale and water exiting felt slightly warm. Friend in the boat googled other possible causes on his phone and found that someone had an alarm due to poor battery terminal connection. Sounded unlikely to me but checked just the same and yes negative terminal on one battery very loose. Tightened her up and ....no more alarm! Mind you we had been drifting in idle for the past 20 minutes.

Last week launched boat and after getting everything sorted to go fishing, motor had been idling for 5 mins when I put it into gear and pushed throttle forward alarm returned and guardian mode activated. So via the isolator I switched from one battery to both (still alarmed) and then to the other and surprisingly the alarm went away???Coincidence? Drove 20 mins to location at planing speed with no problems and backed off the throttle for the alarm to sound again. This time it would not go away and we limped home in guardian mode at 1100 RPM.

I have checked and replaced the impeller and gaskets. The gasket did look a little dodgy and one of the bolt holes for the bolts holding the impeller housing in place needed re-threading. Thought this would definitely be the culprit and the computer was reading lower than expected water pressure. I also attempted to remove the water strainer in lower block but felt like I was going to strip it or break it off so instead I reverse flushed it with garden hose and adapter while I had the leg off. When I took her for a test run the alarm still sounded. Just to be sure I disconnected the pressure sensor and still the alarm sounded. So, not a pressure problem?

Checked thermostat and poppet valve. All looked great with a nice clean gasket, no gunk or sand around poppet or thermostat and no leakage. Just to be sure it wasn't a cooling issue I disconnected both temperature sensors (one in lower compressor and the one in top of block) and gave her another test run....alarm still sounds! By the way the alarm will not sound unless the boat is actually being driven. At home whether in gear or out I cannot get the alarm to sound.

Researched more on the net including this site and found that the oil pump leaking can be a problem. Checked my oil pump and yes it was wet with oil around the lower bolts. Wiped off excess oil and returned in half an hour to find fresh oil there. Have seen how some people have replaced the O-Ring in the pump to fix this leak but I plan to simply replace the whole pump and see how it goes....Yes I will get the Merc mechanics to prime the thing correctly once I have done so (when they can find time for this apparently 2 min job).

HERE IS MY BIG QUESTION: To those of you that have had the leaking oil pump HAS it caused the alarm to sound and put the motor into guardian mode??? I can't find any reference to this. Obviously I need to (and WILL) replace the pump but I'm not sure if is the cause of my alarm????

Sorry for the length of post and thanks in advance

Daz

[JOE54]

leak will not cause horn to sound, find dealer to clear faults, restart when horn sounds read faults , will def show cause of horn , likely tank float in oil res

[justmagic]

Thanks Joe. From my manual however I don't think this motor has the float style of switch in the tank. It does have a "low oil sensor" in the lower part of the tank. So could this be the culprit? Faulty sensor?

[justmagic]

P.S If it is a low oil alarm (even if false, caused by a faulty sensor/switch) shouldn't the alarm be intermittent beeps every 2 seconds?

[JOE54]

deff has float in tank float is what tells sensor its low on oil ,correct it should have intermittent beeps, fault scan would be very helpful in this problem resolve

[Lowerider58]

You could buy yourself a Vesselview mobile unit that pairs to your phone and install it on your motor. It would give you accurate data on your engine when it's running and tell you what faults are occurring. They're on sale from Mercury right now for $150.00

[JOE54]

^^^^^^ good idea for sure

[SilverFox579]

Want to test and confirm? Simply unplug the bullet connectors from the tank sensor and short the boat side connectors together. Alarm stops, replace reserve tank, alarm continues - WARNING HORN "BEEPED".

[justmagic]

Thanks for all the advice guys. Further research shows that (apparently) the alarm beeps intermittently when sensing LOW on oil and beeps continuously if NO OIL (everyone agree?). Couldn't locate the "bullet connectors" but these may have been removed during past work? I'm assuming however the attached image (taken from my motor of course) shows the connection to the oil sensor (can anyone confirm?). I had to loosen all the bolts to the lower cowl in order to move the oil tank up and aside far enough to get at it. It was trapped and hidden underneath the oil tank which was in fact rubbing on the electrical wires but there appears to be no damage or breaks in the outer coating of the wires. Soooo can I please get confirmation that this is in fact the connector to the oil sensor? And secondly now that it is disconnected should I expect to get no alarm if the sensor is the culprit or do I still have to put some kind of connecting wire between two of the terminals??? When you say "short the boatside" SilverFox579 do you mean the oil tank side or the motor side?
Once I hear back I will give a test drive tomorrow and see if we have no alarm. I'm still not 100% confident because if the sensor is faulty and registering falsely that my tank has no oil (IE the magnet is stuck at the bottom of the sensor and making contact) why does the alarm stop if I back off the RPMs? Shouldn't the magnet still be stuck? Any way thanks again in advance for any last minute advice before I give the boat a run tomorrow. Daz
IMG_6499.JPG

[JOE54]

appears to be correct connection if connected to sensor on bottom of tank, alarm will sound until jumpered between harness connection , don't think tank sensor is your problem should not change with rpm reduce

[SilverFox579]

appears to be correct connection if connected to sensor on bottom of tank, alarm will sound until jumpered between harness connection , don't think tank sensor is your problem should not change with rpm reduce

^^^^

Need to jumper the boat side harness, not tank side, to test. I agree with Joe on sensor not likely being your problem. There are several things that can cause the alarm condition you mention. Getting alarm codes read is the fastest and most economical way to identify the problem or at least focus your troubleshooting to the most likely cause/s.

[justmagic]

Yeah like I said the Merc mechanic is booked out for all of February otherwise I would be dropping it of o get the alarm codes.
So what are the "several things" that can cause the alarm condition I mention? Given that I've noted in the initial post I have cancelled out pressure (disconnected water pressure sensor and horn still alarms), cancelled out temperature (disconnected both temp sensors and horn still alarms)?

[justmagic]

So with the motor running and oil sensor disconnected the horn alarmed (as expected) intermittently with 4 beeps every two minutes. With the oil sensor connector shorted (bridged with wire) this intermittent beeping ceased (as expected). Took her for a test run but again as expected the solid, continuous alarm continued to sound at higher RPMs and would go away if I throttled down.
Anyone have any more ideas?

[SilverFox579]

A solid, continuous tone is a critical alarm. You can't find a dealer who will take 10mins to connect the computer to read codes? What is water pressure at idle and at point where alarm sounds?

Know you've been through the water pump take a look at this link and make sure you've done everything precisely as suggested - http://www.bbcboards.net/showthread.php?t=581149

[justmagic]

Thanks again for taking the time SilverFox579 and thanks for the link. Only thing I haven't done regarding any of my pump services is add a fresh bead of silicon to the exhaust bridge. Will definitely rectify this but......

As mentioned in my above posts, like you, I thought it would be a temp or pressure related problem/alarm SO (as mentioned above) I have done test runs with the temp sensors disconnected plus test runs with the pressure sensor disconnected and still the alarm persists. Pressure from tell tale looks good/strong and increases with RPMS
Motor is booked in for March 7th (I know it's only a quick job to do the diagnostics but I'm dealing with the shop assistant and not the workshop mechanics themselves). I really would have liked to get this fixed myself and be back on the water while there are Mahi Mahi and hungry marlin around!

Thanks for your time anyway. Daz

[SilverFox579]

Be sure to report back with what you find out. I still think you might have a cooling system problem. Would be helpful to know actual idle and WOT water pressures. Telltale is compressor outlet only, not cooling system.

[justmagic]

So the problem was the Water Pressure Sensor. Mechanic referred to it as the Block Pressure Sensor (same thing). Was blocked up with corrosion deposits throwing the pressure readings all over the place. I've had the boat out 3 times since replacement and no alarms at all as yet and considering the motor was originally alarming EVERYTIME I increased revs i'm pretty confident the problem has now been rectified. Charged AU$239 for the part, $250 for diagnosis and get this....$250!! for fitting and labour. Now, if you know the part i am talking about here you'll know it can be removed and replaced in the time it takes to type this letter. So I wasn't too happy about that labour charge but I later fitted a new oil pump myself and had them prime it with no charge so happy to let it go for now and keep a good relationship with the dealer. Mechanic was a nice, knowledgeable guy so happy to return to him in the future if need be.
As a side note I did tell the mechanic that I had originally disconnected the pressure sensor wiring harness and driven the boat but still had the alarm sound. He told me that the computer will still alarm in this instance so in attempting to self-diagnose the alarm disconnecting the sensor was not useful to me. Learned a bit more about my motor along the way so just happy to have the boat back in the water while we still have warm blue water around.

[JOE54]

OMG basically 500 for 30 mins work, I just cant do it ,glad its fixed though, I would probly put CROC DUNDEE on his arse,

[SilverFox579]

$239 for the part, $250 to diagnose, and $250 for labor.