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Guardian Mode/IgnitionSwitches Messing Up/Fuel Pump

wkebrdr72

New member
Thanks in advance for any help with this issue:

New to me 2003 Sea Ray 290 Amberjack with dual Mercruiser 5.0 MPI, about 500 hours on each. During sea trial, the port engine would not go over about 2400 RPMs for most of the trial - however, for a couple minutes, about 30 minutes into the trial, it DID go up to about 3100 RPMs for a few minutes, then came back down. The (seller’s) mechanic that ran the boat during the trial said that the boat was going into Guardian Mode and that he needed the Mercruiser computer to hook up to the engine to diagnose what exactly the problem is (he didn't have the computer/program for it). I bought the boat at a discount, knowing the issue needed to be addressed/fixed.

Found a mechanic to look at the boat once I got it to my home marina. He said he did not need the computer to diagnose the issue - said it was the high pressure fuel pump on port engine that was the culprit. I had him change that out, and he finished that job yesterday.
After the change, here is a synopsis of the issue the boat is currently giving me:

port engine high pressure fuel pump replaced

both engines started up fine on the work rack and ran for ~10 minutes in idle and slightly above

Moved boat to the water to run it to see if the RPM issue was now resolved; it wouldn’t start up (20 minutes after it had run fine on the work rack)

on dash - two separate gauges - port side and starboard side

when port ignition switched to ON position, the port side fuel pump does not activate (but DOES activate the starboard side fuel pump)

starboard ignition turned on, starboard fuel pump activates, engine turns on

port engine cranks but won’t turn all the way over and start

leave port switch in On position and turn starboard switch off, starboard engine still runs;
have to turn port switch to OFF position to get starboard engine to stop running

When port engine switch then put into ON position, the starboard fuel pump would activate (still took starboard switch to turn on starboard engine, though)

After running starboard engine for five or ten minutes up on work rack (with garden hose for cooling), then turn off, as soon as either ignition switch is then placed into ON position, I get the single (normal) beep as the fuel pump activates, then immediately get a long, solid non-stop beep until the switch is turned back off (engine is turned off)

Can still start starboard engine, but the solid beep continues until I turn the switch/engine back off (waited for 10-15 seconds, to see if continuous beep would stop - it didn’t).

When port ignition is switched to ON position, the port side gauges work, showing fuel level and battery charge (~12), and when trying to start port side engine, battery gauge goes down and Oil pressure gauge goes up (as is normal, I believe), but it won’t start. I also tried the EMERGENCY START switch with starboard engine running, to jump over port battery, in case the port side battery needed extra juice, but that didn’t work either).

Regarding the continuous beep upon putting the ignition switches into ON position - it does not sound the continuous alarm EVERY time, but intermittently does it (not an intermittent alarm, the solid beep/alarm comes on intermittently, at different times of putting the switches into ON position - hope that makes sense). On those times that the solid alarm does not start right off as soon as I put the switch into ON position, it does indeed come back on after a few seconds (10-20) of having the starboard engine running.

When i start starboard engine, the gauges on the port side (and starboard side) function, showing fuel, battery on port gauge, fuel, battery, engine temp, and oil pressure on starboard gauge.

If i start JUST the starboard engine and do not try to start the port engine, then the starboard engine switch does turn off the starboard engine. HOWEVER, if I start the starboard engine, then put the port switch into ON position (regardless of leaving it there or actually trying to start the engine), then the starboard switch does NOT turn off the starboard engine - i have to put the port switch back down into OFF position to turn off starboard engine.

The mechanic did not mess with the wiring around the switches at all - he merely changed out the high pressure fuel pump on the port engine. He said something about the solid alarm being an indicator of the engine going into Guardian Mode, if memory serves. He said that it seems like there is a short somewhere between the port/starboard switches and wherever they lead to (my words, not his - I’m sure he knows where they lead to). But it’s odd that nothing was messed with regarding wires, switches, etc.

Sure sounds like an electrical issue, but can anyone give any suggestions on where to start looking to try to diagnose exactly what is happening and the fix for this?

Any help is greatly appreciated.
 
Start with the batteries, disconnect 1 battery + cable. See what works and what dosent.
reconnect that cable and disconnect the other battery + lead, see what works.
Report findings
 
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