SOS... Guardian issue

[Etzler]

2008 Mercruiser 350 Mag inboard. Serial no OW698323. Guardian alarm goes off at various Rpms. When the alarm goes off the engine loses power and won't reset until the power is retarded below 1000 rpm. Sometimes the alarm won't go off until your over 3500 rpms. Then another time out, as soon you hit 3100 the alarm goes off. Today the alarm went off at 3100 rpms. . We decided to find a cove and relax.. After about an hour or so we restarted, couldn't go above 2100 rpms. ( some sort of temp issue?). Had it at the shop to check for codes and none were found. There was a concern about the fuel pressure, it sits around 32 psi. Should the fuel pressure be 43 psi? I believe that's what the cool fuel regulator is. History. The boat sunk in 50 ft of fresh water. We replaced the 555 computer, injectors, and most of the sensors. Any help would greatly appreciated.

 

[achris]

"The boat sank in 50ft of fresh water"

Basically, all bets are off. The problem could be anything you didn't replace. Once submerged, ALL electrics need to be replaced, all engine sensors, starter motor, alternator, HVS (looks and performs like distributor), ignition coil, fuel pumps and, most importantly, the wiring harness.

You're also going to need the computer on the engine when it fails. Some faults don't get recorded, they just set guardian mode. Once the fault clears, there is no code to read.

And yes, your fuel pump pressure is too low. 43psi is what it should be.

Chris. ...

 

[alldodge]

I do believe your pressure should be above 32 psi and should be in the 43 range. Cannot say with 100 percent certainty because I don't have a manual for your motor, only 31 which is for 2001 and a bit higher.

Just for stinkers and giggles, go to the shift plate and find the gear switch. This switch tells the ECM if the boat is in gear and not in neutral. If it thinks its in neutral it will go into guardian mode. The pic below shows switch positions for Alpha and Bravo drives. Find the Gear switch and disconnect the switch, it will not change anything on the ECM. If it goes away then the switch needs replaced or readjusted, or leave disconnected

 

[Etzler]

Update. I think we may have fixed it. Replacement of the cool fuel pressure regulator appears to have restored fue pressure to 38 -41 psi. On the first test run we got the RPMs up to 4500-4800. Seems to run great. Hopefully this does it.

 

[alldodge]

cool :thumb:

 

[Etzler]

Well that didn't I do it. Very disappointing. Second trip out we are back to the 3200 rpm alarm. After it warms up and sits for awhile the alarm comes on at 2300. Changed high pressure pump again to confirm it wasn't getting hot and failing. No change. Changed the coil out, with a spare I had, nothing. When I put the boat in neutral I can run it all the up to 4500-4700 before I get an alarm. Not sure if the same thing is setting the alarm off, and if engine load is affecting the alarm, or they are separate alarms.

 

[alldodge]

Same alarm but may be sounding off for different reasons. Did you try the neutral switch?

 

[Etzler]

Same alarm but may be sounding off for different reasons. Did you try the neutral switch?

It's an inboard. No interrupter switch that I know of. Gong to test the water pressure. I have read that the pump housings can be worn. Temp world remain in the correct range, but psi can be low. I am just shot gunning this thing at this time..

 

[alldodge]

It's an inboard. No interrupter switch that I know of. Gong to test the water pressure. I have read that the pump housings can be worn. Temp world remain in the correct range, but psi can be low. I am just shot gunning this thing at this time..

In post 3 I wanted to know about the neutral safety switch, sorry but since you didn't tell us it was an inboard I'm sure most assumed it was a stern drive. But what do I know :noidea: Only know what you tell us. Even an inboard with your serial number has a "Neutral" safety switch and its on the transmission. See item 20 in the link below

http://www.mercruiserparts.com/bam/s...1606/12841/250

Hope you figure this one out, Think I'm done

 

[Etzler]

In post 3 I wanted to know about the neutral safety switch, sorry but since you didn't tell us it was an inboard I'm sure most assumed it was a stern drive. But what do I know :noidea: Only know what you tell us. Even an inboard with your serial number has a "Neutral" safety switch and its on the transmission. See item 20 in the link below

http://www.mercruiserparts.com/bam/s...1606/12841/250

Hope you figure this one out, Think I'm done

Thanks. Sorry for the confusion. I will check the the safety switch.

 

[Etzler]

Tonight I replaced the temp sensor for the ecu. Huge improvement. Able to run full throttle. Shut it down for half and hour to let the heat set in. Went in to gaurdian a time or two after sitting, but we were north of 4000 rpm. I checked the water pressure at 4000 rpm, it was registering 10psi. What is normal psi for a raw water pump?

 

[Etzler]

Hopefully this is the final post. After replacing most sensors, I think I figured it out. Defiantly seemed like a sensor or something malfunctioning with temperature. Final replaced the ECU oil pressure unit. Seems to have fixed the gaurdian issue. Even went as far to swap out the good sensor with the suspect one. After swaping, the guardian mode issue returned. Fingers crossed that 'tis is it..