350 MAG won't rev past 3400 rpm, sounds like rev limiter

[bortSanders]

Thanks for your input AllDodge.

O2 sensor A 180
O2 sensor B 102
O2 sensor C 76
O2 sensor D 728
- I'm not familiar with these numbers. Im guessing it is block learn of some sort higher numbers reflecting a rich mixture?
- Which letters are which, pre and post cat?

Ignition Parts-
-We were careful to order the correct cap because we got screwed by an aftermarket cap last year when an earlier vintage (2007 ish) 350 mag wouldnt restart after an ignition tune up. These are my notes from my service history- we ordered from land'n'sea.
wires 710-84-863656a or 863656A1 $91.26, rotor 710-8m6001222 or 898253013 $13.23, cap 555ecm 710-8M6001106
-no I didn't gap the plugs. My understanding is that iridiums shouldnt be gapped (for many reasons) based on info straight from NGK and Denso's website. I did carefully check them with a wire gauge to ensure the gap was uniform. I believe it was around some where around 041-.044".

I put the codes in order. I appreciate you transcribing them.

Fault
22 Exh Man overheat port - 13.0V 0.0hr
19 Guardian overspeed exceeded 5423rpm 14.3V 198.9hr
9 Guardian 14.7V 199hr
321 Port side fuel lean 1593 rpm 14.4V 204.8hr
314 Stbd Cat failed to run properly 14V 352.0hr
355 Stbd O2 fault 13.4V 360.3hr 360.3hr
390 Strb Stuck rich 1909 rpm 14.5V 370.6hr
3 Sea pump low 0.0 psi 14.4V 401.6hr
2 Bat voltage low 7.8V 470.3hr engine stall
12 Low oil pressure 2.9psi 951rpm 14.4V 611.8hr

That last low oil pressure was from the oil change I did. Had low oil pressure when it started til it pressurized.

We put a new starboard side post cat o2s in last year. Im curious if a cyl 8 misfire is sending hot raw fuel into cat causing those starboard side codes.

The low battery was one of our boneheaded renters. I put 2 new batts in around that time.

The sea pump code is probably from winterizing.

***That gaurdian overspeed is a little interesting. Rental boat. Then I have a port side lean code 5 hours later. Same side as my misfiring cyl 7. I wonder if the high rpm floated a valve or something. The owner told me this boat hasnt been totally right for a 2 or 3 seasons.***

Next step is definitely a compression test. I just gotta haul all my gear out there and do it when its not raining.

 

[alldodge]

I'm sure all parts replaced are in good shape, was just a comment if they were not replaced.

O2 sensor A 180
O2 sensor B 102
O2 sensor C 76
O2 sensor D 728
- I'm not familiar with these numbers. Im guessing it is block learn of some sort higher numbers reflecting a rich mixture?
- Which letters are which, pre and post cat?

Don't know which sensor is in which position. Do assume one is before and one after the CAT. No matter which way I look at it, something isn't right and do wonder why there is no code

when its not raining.

Sure could use some of that here

It is a puzzler, don't know if this method of timing would help

View attachment HVS clocking Bulletin 2011_11R2.pdf

 

[QBhoy]

Hi
every single time my diz cap has failed (5 times in 5 years, one of them out the box) it has recorded a misfire on a couple of cylinders. Every time. Honestly, check that cap. Never trust them. Even if they are recent.
The shift interrupt switch failure also caused a misfire error code too. But that’s on an alpha. Forget which drive you have and can’t go back to look whilst typing

 

[muc]

O2a=port-pre
O2b=stbd-pre
O2c=port-post
O2d=stbd-post

Unfortunately your test run didn't spend enough time in full PID (closed loop) to get enough info to troubleshoot.
Next time you run the boat. Hook up Diacom, start the engine cold, start Diacom, drive the boat out past minimum wake and once warmed up, accelerate to 2,000 RPM for 2 minutes,3,000 RPM for 5 minutes, 3,500 RPM for 5 minutes, 4,000 RPM for 5 minutes, then slowly increase to wide open and hold for 1 minute. Return to slip/trailer and stop Diacom. This should give enough info to determine your problem.


You posted this in your first post but I didn't see that during your run.
"Won't rev past about 3400 rpms. Won’t plane out, Sounds like the rev limiter kicks on and stumbles"
You got over 4,000 RPMs during the run?

You need it to act up during the recording, so you should figure out how to get it to act up.

 

[spunkyman]

I have the same problem on my 2014 350 MAG. I can't get past 3400-3500 RPM without complete limited power and backfiring. It's never run correctly. I have 8.4 hours on it and i was able to swindle a Merc guy to my house and he ran the scan tool with no errors.... told me I wasn't firing on #7 . . He said to change the plugs (but I only have 8.4 hours on the engine) OR it could be an injector. Did you test or change the injectors? I'm wondering if maybe it's my Rev limiter, because when I get to that point (3500 RPM) the engine tells me "that's all i have!".... frustrating to say the least ! I will follow the thread in hopes we both find relief. I'm believe my plugs are MR43LTS ... I was told to try NGK 5599.