mess

Hey OSO experts I need some trouble shooting on a problem I am having. I have checked all fluids and fuel. The boat runs fine until you go over 4500 rpm then go's into guardian mode.As soon as I throttle back to idle the engine is fine. The engine go's into guardian when the engine is hot or cold.All gauges are in normal ranges. My thought is a faulty sensor. I am schedule to have it checked out by my mechanic.Just thought I would get some thoughts from the OSO experts.

bowtie

What year and make and model. Sounds like a Volvo to have guardian mode. They have temp sensors on the risers that will do this, the older ones had a problem. You can just disconnect them and should come out of guardian mode if this is the problem.

mess

bowtie,
I have a 2006 sunsation 288. I know there is a guardian system on the 496HO. I tryed to remove a sensor wire on the manifold but the buzzer went off when I started the engine ,so I reconnected the sensor and decided to not try anything else.

Dave_N

There are several possible reasons for the alarm. Without a scan tool you just can't be sure what it is. There have been a few threads recently about IAC failures/alarms on the 496HO recently. It's a very common failure and may be the most likely cause.

Dave

mess

Thanks Dave for your input. I did have it scanned ,but he worked it in before I went on vacation and did not have the time to fix it. He did'nt act like the infomation from the scan tool was a big deal.I will sure let him know about IAC failures/alarms.

Dixie Doug

IAC means Idle air control.Not a problem at 4500.
Low water pressure(bad sea/pump) or low fuel pressure(plugged fuel strainer in the pump)

Reckless32

You have the 2 beep per minute "soft" alarm where it's only putting in partial guardian, or limiting your horsepower to 90% which puts you at 4500. Probably getting full alarm there too. You have to reduce rpm's below 1100 to get it to go away.

There are several non-critical faults that goes soft. Hard faults are for overheating, oil, and drive oil where it will reduce to 6% and enough rpm to idle back home (at driver's risk).

Nail down the scan faults and go from there. Make sure he checks the history where the last 10 detected faults are stored. Most likely one of the sensors.

If you disconnected a sensor and got an alarm and it went away, it most likely is working fine. Try the others as well.

mess

Thanks Guys,
I will have it checked out. I really appreciate the help.

mess

Hey Guys,
Just thought I would update you on my boat. I had my mechanic check it out.The boat would go into guardian at 4570 rpm. They hooked it up to the laptop,but there were no codes that came up. Call Mercruiser and they sent a crankshaft sensor and that fixed it.