496mag Guardian Mode - No Fault codes HELP!!!

We purchased a
2006 Laser Blade
496 Mag
Barvo 1 drive

Motor is putting itself in guardian mode and throwing no codes.
Boat ran fin for 1 run..... UGH

Now it will only go up to 3000rpm in guardian

Work Done so far....
At essex-
New Impeller
New impeller housing
New Plugs
Annual service
Compression test

Another shop...
Ran Computer no codes
New water pressure sensor
External water pick up tube installed

After this the motor was in guardian...Then would break free for a second and RPMs and speed would increase to a normal level!!

Don't have tons of money to put it in the shop to play chase... Anyone had this issue before??

Fuel related. No codes will show. Start at the pump. work your way up.

Also why the external pickup on this setup? Pointless.

Runs2rch said:

Fuel related. No codes will show. Start at the tanks. work your way up.

Also why the external pickup on this setup? Pointless.

Click to expand...

You misspelled a word .........

If it's actually going into Guardian mode, it WILL show in fault seconds with the Merc CDS. It may not throw a code but will be able to see when and why it happened. If they didn't use the CDS, it may not show up.

I guess what I'm saying is to have it looked at by a Certified Merc tech that has the CDS. It will save a lot of time.

"fault seconds" may not go into the memory, the 'fault event' may be so quick and short that it is not recorded by the ECM .

This was a big problem with 305 Mercruisers in pontoon boats . The 'harmonic vibrations' actually set off the 'shift interrupt' in high RPMs .

Merc changed the 'RPM limits of shift interupt' to cure this problem .

A water test with a CDS on board should reveal the problem and then the cure ...............

Runs2rch said:

Fuel related. No codes will show. Start at the pump. work your way up.

Also why the external pickup on this setup? Pointless.

Click to expand...

We did this because that is what the second person suggested to do

Husband just ran a fuel pressure gauge off the fuel rail...

Prime Pressure - 60psi
Idle - Bouncing between 50-60psi
Reed up - Dropped to 40psi

Is this normal range?

AzGeo said:

You misspelled a word .........

Click to expand...

Hahaha yes.

I assume too much. Which def should not. I figure even the most novice novice knows to to start with the tank(s).

christen63 said:

Husband just ran a fuel pressure gauge off the fuel rail...

Prime Pressure - 60psi
Idle - Bouncing between 50-60psi
Reed up - Dropped to 40psi

Is this normal range?

Click to expand...

Unfortunately no the fuel pressure is to high..Should be more of a steady 40 - 42ish psi.

Re-check your spark plugs for a fuel fouled condition.

Being the pressure is to high, chances are your fuel pressure regulator system is going to be clogged up by debris "possibly" paint from the gen 3 cool fuel system....Don't run the engine until you determine if that is the case or not. It could spread further upstream into the fuel rail, fuel damper & injectors if it's not there already.

Also inspect the bottom side of the Gen 3 cool fuel module "top cover" which is the lower side of the fuel regulator and of course both of the fuel filters all which are going to be item numbers 2, 10, 21, 26 in the following link for a starting point for you, http://www.mercruiserparts.com/bam/subassembly/31827/12826/60

If you decide you'd rather have/find a final resolution to your engine running issues, consider calling BDMar (Brian @ B & D Marine) as this is what he does day in day out.:thumbsup http://www.bdmarineperformance.com/

Hope this helps, good luck.

I don't know much about the merc ECU...but I can tell you it isn't going into guardian "just because it feels like it"....there is a fault code you just more than likely are not using the appropriate interface to see it.

this doesn't make sense either:

Prime Pressure - 60psi
Idle - Bouncing between 50-60psi
Reed up - Dropped to 40psi

Click to expand...

if your fuel pressure is 60 psi (key on prime) and drops at idle this is normal if you have a manifold referenced pressure regulator. "Reed up"?? do you mean SPEED the engine up? not enough info here....if you are driving the thing and under load and speed the engine up pressure should increase not decrease.

PCM crystal failure. Call whipple for repair. 620 dollars with shipping back to do it.

The engine needs to be plugged into CDS and see if it is actually going into Guardian mode. If the engine is going in Guardian mode it will reveal a trouble code.

Found this as I do not post very much up here. One thing that was not mentioned is AVAILABLE POWER from a scan. If the available power is showing 100 % on the scan --- IT IS NOT IN GUARDIAN MODE as you are running the down the water ways. If guardian mode is taking place - it will show a fault(s) and show a certain percentage of available power LESS than 100 %. Also look into history on the scan and it will show the faults as to what they are at per timeframe of engine hours.