496 Mag HO RPM issue
#11
Registered
You can try swapping the props from side to side(run shifter in reverse for test) and see if issue follows. That would take the props out if the mix.
#12
Registered
Thread Starter
Join Date: May 2021
Posts: 10
Likes: 0
Received 0 Likes
on
0 Posts
#13
Registered
Apologizes, should have taken more time to really read the issue
The does it IN THROTTLE ONLY MODE is the give away that it needs to be re-calibrated
The does it IN THROTTLE ONLY MODE is the give away that it needs to be re-calibrated
#14
Registered
Thread Starter
Join Date: May 2021
Posts: 10
Likes: 0
Received 0 Likes
on
0 Posts
I'm also wondering about the fuel trim. I know auto engines adjust but on these non-cat EFIs are there any fuel trim adjustments with no O2 sensors?...my understanding is there is no verification. The MAP along with everything else can provide the PCM with info to set the injectors but will it make adjustments based on burn? If there is a long term fuel trim adjustment I could see that being an issue. Trying to get a better understanding.
#15
Registered
Dealers and others with "I think" the Merc G3 computer can Cal. Do a search on line and there are several companies
With out )2 sensors, the PCM just uses the Fuel tables programmed into it. If the MAP, TPS, ECT or fuel pressure changes, then the PCM only works with what its provided
With out )2 sensors, the PCM just uses the Fuel tables programmed into it. If the MAP, TPS, ECT or fuel pressure changes, then the PCM only works with what its provided
#16
Registered
Thread Starter
Join Date: May 2021
Posts: 10
Likes: 0
Received 0 Likes
on
0 Posts
Dealers and others with "I think" the Merc G3 computer can Cal. Do a search on line and there are several companies
With out )2 sensors, the PCM just uses the Fuel tables programmed into it. If the MAP, TPS, ECT or fuel pressure changes, then the PCM only works with what its provided
With out )2 sensors, the PCM just uses the Fuel tables programmed into it. If the MAP, TPS, ECT or fuel pressure changes, then the PCM only works with what its provided
If anyone has any other ideas in the mean time I might be able to try I'm listening.
#17
Platinum Member
Platinum Member
Thanks. That's kinda what I thought about fuel trim. With no burn verification it can't adjust long term...or short for that matter. I will try and get a tech with Merc computer to the boat. I just wonder why it would go out of calibration all of the sudden? For the previous 3 plus years of owning the boat the RPM were dead on unitl the end of last season.
If anyone has any other ideas in the mean time I might be able to try I'm listening.
If anyone has any other ideas in the mean time I might be able to try I'm listening.
#18
Registered
Thread Starter
Join Date: May 2021
Posts: 10
Likes: 0
Received 0 Likes
on
0 Posts
I don't believe I have a MAT sensor. If I do could you please elaborate on where that would be. I did swap the MAP sensors which resulted in no change.
#19
Platinum Member
Platinum Member
Boat is located in Lorain, OH on Lake Erie. There are dealers/repair shops out west but probably would have to get the boat to them and who knows how long they would want if for. Sucks losing time during our short season. The boat does run and can be used so I'm trying to troubleshoot without having it at a shop for an extended period. Hopefully I can get someone with the Merc computer to come out to the dock.
I don't believe I have a MAT sensor. If I do could you please elaborate on where that would be. I did swap the MAP sensors which resulted in no change.
I don't believe I have a MAT sensor. If I do could you please elaborate on where that would be. I did swap the MAP sensors which resulted in no change.
#20
Registered
Believe its out of Cal from how its acting. Doing a re-Cal might show that one of the sensors is out of spec so its telling the PCM incorrect info. Drive by wire is great until it doesn't work as we all know, Hope there are others with more smarts then me