350 MAG Mercruiser Alarm on Startup

CaptianDan

Does anyone know if you should hear one or two beeps when you turn the ignition on from the audio alarm (I have no alarms when engines are running)?  I have read it should be one beep and two if there is a DTC fault present but wanted to check with you guys to see what you have.  I have a 2002 342 FV with 350 MAGs with engine serial numbers starting OM00xxxxx.  Both engines have the same issues.
I haven't got any fault codes from a scanner but I am experiencing some RPM restriction to approx 3000 RPM on both engines which leads me to think this might be a guardian issue.  Appreciate any help! 

Cableguy Greg

You should have one beep when you turn the ignition on. It should then go away. If you can't get over 3000RPM, they more than likely are going into guardian mode.

CaptianDan

Thanks Greg.  That was my train of thought with 2 beeps on startup but it's thrown me that I can't see any fault codes or have any further audio alarms when using either engine.  I was wondering whether the RPM limitation was something else.

reneechris14

If you turn the battery's off it should reset the code.

davidbrooks

Anything that prevents you from going over 3000 rpm will be stored in fault history.  Also when connected while engine is running you will see it as a active fault. 

CaptianDan

Thanks @reneechris14 I will try that.  @Alswagg It was scanned by my local mechanic using a Rinda MST scanner below.

@davidbrooks using the scanner we have there are no fault codes while the engines are underway and being restricted at around 3000 RPM.

Thanks guys.

CaptianDan

@Alswagg Thanks Al, I have had a run out with this scanner plugged in and see no faults and none in history while under power.  I have also tried to get to WOT but it still bogs at around 3000rpm on both engines with scanner plugged in.  Still no faults.  Would this scanner pickup everything?  I'm wondering if I'm missing a fault the diacom would pickup.  The mechanic and I are at a loss.

212rowboat

the scanner won't know about an air restriction.  what kind of condition is your flame arrestor in? 

CaptianDan

Flame arrestors are in good condition but that is a good point about air restriction. Is there any thing else that cause air restriction that would not trigger a fault? 

davidbrooks

Puzzling. Especially that it is on both engines. What did you have on  the "available power" setting? Really serious faults should be a constant tone.  But not understanding how it could be in guardian mode without an active fault.

CaptianDan

@davidbrooks That's what is puzzling me, unless it isn't in guardian mode and something else is restricting the RPM to 3000.  Let me see if I can get the report of the mechanic to post.  This has been driving me crazy for months now.

Liberty44140

Are both engines pulling from the same fuel tank? That would be one of the only constants for both engines. 

planesailing

I have a 5.7 efi Merc that also had 2 beeps when ignition is turned on and then 2 beeps once engine is started. No further beeps after start up but mine also seems to big down around 3000 rpm. Sometimes manage to get 3500rpm but thats a struggle. Could mine also be going into guardian mode? Is there a way to plug mine in to check for codes or is 2 beeps normal on my engine?

CaptianDan

@Liberty44140 Each engine has its own fuel tank.  @planesailing Sounds like the same symptoms as mine, could be a guardian issue. Plug a scanner in to check. Depends what ECM type you have as to what codes you receive.  Both mine are MEFI 3.
Thanks for the ideas so far guys. Any more please pass them my way. Cheers.

Lake_Bum

My 350 mag also has two beeps, only when key turned on, not after started. But I have no rpm issues. Boat seems to running great.....is 2 beeps always a red flag??

Willhound

Lake_Bum said:

My 350 mag also has two beeps, only when key turned on, not after started. But I have no rpm issues. Boat seems to running great.....is 2 beeps always a red flag??

Mine the same. I think maybe a previous fault from a leaking drive oil reservoir line that caused a low oil warning that never got properly cleared even though rhe problem is fixed.

Robs_232

Have you tried unhooking your battery cables for a while then reconnecting them? I think this will make your ECM's reset once powered back up. Al might shed more light on this. Just thinking outside the box.

Lake_Bum

That is the issue I had as well, some drive oil had leaked out, and the reservoir was low. I can't remember though, if I had one or two beeps before haha. 

CaptianDan

I'm going to try removing power today to both engines for 30 mins then powering up again and retrying.  I'll let you all know what happens.

captpaul

do you have cool fuel filters?

CaptianDan

I do have fuel coolers but I have stripped these and replaced both regulators.  Looking like good vacuum too.  I'm at the boat from tomorrow morning so I'm going to try and diagnose this from the start again. Wish me luck! :-)