What about these 430 degree "lake temps" on every report? Is there steam in cooling sytem where your supposed to have water? Smitty

ok,
Just wanted to add one thing. There is no doubt that it is going into Gaurdian Mode. You have a Gaurdian Mode Fault with multiple recent occurances.

The question is why, and why is it not generating a fault code. I still think the Sea Pump Pressure sensor needs to be checked. But there is one clue that I overlooked (GOODT touched on it) and that is that Sea Pump Pressure should only cause a reduction of Available Power to a minimum of 6%. But we see that the Available Power in the last two stored freezframe faults is at 0%.

There are only two things that should be able to cause a reduction to 0%, that is Low Gear Lube and Low Oil Pressure.

Could it be that the oil pressure sensor was damaged due to excessive boost? Just a WAG, and I still can't explain why no fault code.

Dave

Smitty,
I believe that is for Smartcraft lake temp sensor which this does not have.

Dave,
I will check that and I did forget to mention one occurance; A very loud backfire (exhaust) when first attempting start up on the hose.

Linnie,
I'll call you in the morning.

Thanks Guys and keep the thoughts coming. I need to do a data log while it's running and see what the sensors are doing when it dies. The cam sensor is 5 days out

Dave

The only thing that stands out to me may be the fuel flow. The cam/ Crank faults are generally something that occurs on start up if they are not active codes. It would appear to me this is not an electrical problem, but a fuel starvation problem. Not sure what year your boat is, but the older 496' had an issue with the boost pump inlet screens plugging up. The fix, to prevent this was the addition of an in-line filter. If you do not have this filter, I would check this out.

Thanks Island Hopper,
Again, I believe the fuel flow reading is a Smartcraft feature which is not installed on the motor. Also, the fuel system is a Whipple setup with all the other garbage removed.
When my personal stock 496HOs run dry (one time learning the tank system ) it sputters and craps out slowly. This occurance is like someone shuts off the key.

Thanks,
Dave

Something interesting direct from the Merc PCM555 manual….

“With software prior to level 091, a malfunction of the crankshaft position sensor or camshaft position sensor will not set a fault. With level 091 software, if the camshaft position sensor is bad and does not send a signal to the PCM, the engine will backfire and not start. Stop cranking the engine when this occurs and then try to start engine. Operate the engine for 20 seconds to set faults.”

Boy does this sound familiar ????

Dave

Well, Well, Well..............
Diacom was well worth the purchase.

Even with my deep skeptisism the tool proved itself worthy.

We pulled the old and in with the new cam sensor and she idles like new (except with a healthy cam ) and puts out no errors

Off to the lake for some testing.

BTW, the sensors can be bought from AC Delco for half the cost of Merc. Merc even leaves the AC Delco number on them

Thanks for all the input.
Dave

what is the AC Delco number ? Glad to hear your running

Yes, what is the AC Delco number? Did they just look it up from the truck motor parts book?

I don't recall right off hand but the GM numbers are physically on the cam and crank sensor.