Combing over these forums, I haven't stumbled across anyone representing a similar problem.

First time out this year and having trouble with the Starboard side drive engaging, so before I really get a chance to add fresh gas or even run the boat I take it in to have have the drive looked at. The service center replaces the shifter fork and cable and I'm thinking this will be the cheapest start to my year.

Well I fill the tanks with some fresh petrol and head off to the lake and I'm immediately thinking the boat feels lazy and my top speed is off 6-8 MPH. I didn't think to much of it and just put it off to extra gear, flat water, driver error....the following weekend we set off for LOTO where I'm sure the rough water and ample space will allow me to find the sweet spot again.

So the first time out, I'm looking for those numbers and notice every time I pull out of the sticks fast, the Starboard motor goes into guardian mode. It will remain that way until I leave the Starboard throttle positioned at idle for a few seconds then I can hit it again.

Not knowing any mechanics there I feel I should get my finger nails dirty and have a look. All my fluids look normal then I recalled the shifter cable replacement...I think to myself, what are the odds a plug wire came off the #6 or #8 cylinder during the cable replacement? I lay on top of the engine cowl and sure enough, #8 wire was laying in the bilge. This has got to be the reason for the power loss and intermittent guardian issue right?

I plugged the cable back in, fire up and the motor sounds the same so I take it out for a spin expecting to see the numbers again...wrong. Zero difference and guardian still kicks in on that motor if I pull off the stick fast. Okay, well I'm thinking maybe the coil or wire was damaged from the shifter cable pulling it off...maybe the plug is fowled from days of use with no spark, so I changed plugs with one from the Port motor and checked for spark...all looks good.

So we finished our vacation working around these limitations and took it in immediately for service. The mechanic pulled the codes noting guardian mode had been activated but no smoking gun. He also checked fuel pump pressure and told me those were fine as well. So he cleared the codes, topped off the drive lube and asked me to run it again.

I ran it over the weekend with no change, but I did spend some more time looking at it. At idle, it sounds normal, but if I tack it up to 3,000 RPM in Neutral there is a notable vibration compared to the Port side under same conditions.

Anyone have any thoughts? Am I looking for a link between the plug wire, guardian and power loss that isn't there? Comments are appreciated, thanks.

just a couple of easy suggestions... pull the plug out of the hole where the wire was off , throw it away and put in a new one. i know its unlikely it was fouled to the point where it wouldn't clean up but for 2 bucks its an easy check.

second, check the firing order. that was quite a good piece of reasoning looking for the "off" wire but carry that to a logical extreme... maybe they knocked more than one off and put them back incorrectly...

One of the big points of using a scan tool to identify what trouble codes are is to look at the history file and see what the guardian event actually was or what registered the guardian event.
Question: what was the guardian event listed as??

Best Regards,
Ray @ Raylar

Thanks Steve and Ray.

@ Steve, Since I was in a pinch at the docks, I removed a plug from the Port side #2 cylinder and switched it with #8 from the Starboard, made no difference. Also while I was down there, I checked the wires from the coil overs to the plug, it appears only #8 came off.

@ Ray, it figures we have a crazy storm roll through here Monday morning. It has knocked out power and many forms of communication in Northern IL. so the service center has been shut down and I've been unable to get an update on what the guardian even is registered as.

oh well...sorry. at this point it would become a standard diagnostic exercise for me... scanner, codes, fuel pressures/ flow/ fiters strainers... chk and confirm all the easy stuff followed by the harder stuff. i am just really suspicious when it runs good and work is done and then it doesn't sort of thing... 99 out of a hundred its something somebody bumped or broke or leaned on and knocked off... but that's nothing more than guesswork and conjecture on my part... sorry no help here.

yup, I'm right there with you Steve which is why I typically like to do all the work myself.

Who is working on it???? GSC? the viberation is a dead miss which is most likely a bad or plugger injector and most likely # 8..check your oil for gas fumes,if the injector is working and the cylinder was not fireing you may have fuel in your oil which will tell you the injector is working..

if you need better dianostics done im not far from you,pm me

Thanks for the insight MrFixx. I have the boat with Water & Wheels, Keith is the only one I trust other than myself. Talked to him this morning and he finally got power back yesterday, should have some data this afternoon. Are you on the Chain?

lombard area,i have a friend on the chain (donovin's marine) i help him from time to time on the efi and performance stuff.I also boat their..

IAC valve, or a failing boost pump thinking outside the plug/wire box. If IAC you will get full alarm and guardian restricting rpm's to either 3k or 4k I forget, then full alarm won't go away until you back off below like 1100rpm. Then you get a beeps every two minutes. It's minor or soft guardian.

If you have a fuel pressure gauge with a shrader valve connector (if not buy one from auto store cause they're handy) connect it to the injector rail on top and see where it's at. Should be somehwere in the 38-42 range steady. If it goes there for a bit and slowly drops off, then your boost pump is crashing.

IAC's are very common problem with 496HO's. Follow the hose back from the intake to the rear of the to rear of the engine. That's the IAC (Idle Air Control). Retail they're like $120-150 or something like that. Since you have twins? you could swap out the two to check if the problem moves to the other.

If not, try what was suggested above....Re-trace your plug wires to ensure they are connected #1-8 in the proper firing order. I screwed that up a few times on my older carburated boats & cars with similar symptoms.

Otherwise guardian results from sensors. Water, fuel, ignition, IAC, MAP, etc. Then it's provess of elimination again, depdning upon the scantool code history. I bought a Rinda scantool after i bought my twins and it has paid for itself twice three times over.

Good luck.