4.3 mercruiser overrev alarm

[Egoodwin]

I have a 2006 sea ray 290. Twin 4.3s w bravo 3s. It starts runs and isles fine. New oil change, battery’s and fuel water separator filters. In neutral or under load once my rpm’s reach 3500 I start getting an over speed alarm. It’s been this way since I got it a few years ago.

 

[dubs283]

Being a bravo I'd first suspect in/out gear switch. Similar to an alpha in appearance, but only tells the ecm (efi only) whether or not the shift plate/cables are actuated in gear or out gear (neutral)

Only true way to know for sure is connecting a diagnostic tool that can verify current/previous fault codes

FYI 3500 rpm is a bit high for neutral speed

 

[Egoodwin]

I only checked it in neutral bc I was struggling to get it to 3500 under load. Where would I go to find the in/out switch. The boat shifts into forward neutral or reverse fine.

 

[dubs283]

Where would I go to find the in/out switch.

Located on the shift plate assy, as stated it looks like the shift interrupt switch for an alpha setup. The switch allows the ecm to know if the drive/cables are in the "in gear" position. Alarm would be sounding for over rev in neutral.

FYI if the engine is struggling to achieve 3500 rpm under load you have other issues as well. Tune up, fuel supply/quality, etc.

Best to get/borrow a diagnostic tool to check fault codes/history

 

[alldodge]

Disconnect it

 

[Egoodwin]

I have a bravo 3 drives. Both motors give me the overrev alarm at 3500. If I disconnect the gear switch would that stop the alarm? What other problems could it be? I’m headed out to the boat in a few hours I’ll post a video of what it’s doing.

 

[dubs283]

If I disconnect the gear switch would that stop the alarm? What other problems could it be?

Maybe, if it is indeed the switch triggering the alarm.

If not, it could be any number of issues causing the alarm. This is why you need a diagnostic tool to verify exactly what is causing the fault. Otherwise you're just guessing, and that gets expensive quickly

Seeing as how both motors cause the alarm it may be something with anything that is shared between the two. Fuel is the main thing that comes to mind but 2006 ecm does not have a fuel related fault save for knock/misfire. When was the last full tune up performed?

 

[QBhoy]

Hi. I just responded to a similar post on a 350 mpi with bravo.
I’ll say similar for this post. Warning. Could be way off the mark…but here it is.
If you have your drives trimmed up into or near the trailer height, there might be a rpm limiter for the sake of mechanical sympathy. Certainly my modern merc outboard does.
Also now commonly known to cause issues if the trim limit or sender (one of them or both perhaps from memory) has problems. Meaning it can cause a limit of rpms under normal operating conditions.
But in your case and especially if you have the DTS controls…and reading that you are perhaps on the trailer and perhaps in a condition having the drives up a little, you are probably just getting what it’s supposed to do ?
Like I say…could be way off..but there is my two bob !

 

[dubs283]

Could be way off the mark…

Like I say…could be way off..

Agreed

Mercruiser trim faults aren't set according to engine rpm and given the vintage only occur with smartcraft.

 

[QBhoy]

Agreed

Mercruiser trim faults aren't set according to engine rpm and given the vintage only occur with smartcraft.

Is this for sure ? Il thought that these set ups have a rpm guardian in trailer mode set by the trim sender ? These have smart craft and DTS functionality. Worth a look into for sure.

 

[dubs283]

Is this for sure ?

Yes

Il thought that these set ups have a rpm guardian in trailer mode set by the trim sender ?

No. I've never seen, heard of, or read anything about a trim fault based on engine rpm/limit with 555 technology.

These have smart craft and DTS functionality.

You sure? OP hasn't posted much info regarding set up/serial number.

Unless there has been a massive upgrade it'd be odd for a twin 4.3 merc setup to have DTS given the vintage/brand

 

[QBhoy]

Agreed

Mercruiser trim faults aren't set according to engine rpm and given the vintage only occur with smartcraft.

So just as an additional and respectful reply…
For sure these engines have smart craft. My older 2003 mpi has the ability. But doesn’t have the rpm limiter in neutral or trailer/high trim mode, admittedly. But later mpi from the mid 2000’s certainly have the limiter in neutral.
With regards to the earlier off the top of my head and guessed assumption that it may have a limiter at a certain height of trim tilt, like the outboard I have certainly does, having glanced at a few things I have on the laptop here, it looks like these of a certain era around then (or close), that have bravo drives and especially with DTS (like I assumed), will have a rpm limiter in place at a certain trim tilt level. See what you think yourself, if you have any manuals that might confirm. All the best

 

[QBhoy]

Yes

No. I've never seen, heard of, or read anything about a trim fault based on engine rpm/limit with 555 technology. And I've seen a lot of mercs

You sure? OP hasn't posted much info regarding set up/serial number.

Unless there has been a massive upgrade it'd be odd for a twin 4.3 merc setup to have DTS given the vintage/brand

Just assuming the odds on the mention of 2006 4.3’s mated to bravos…likely being mpi engines. All 4.3 mpi engines are 100% smart craft compatible. I’m certain on that at least. Like I say. I have a 2003 mpi that currently uses smart craft. Honestly not sure about DTS in the late 2000’s. No idea if it would be a thing then or not.

 

[dubs283]

For sure these engines have smart craft.

Never said it didn't

it may have a limiter at a certain height of trim tilt, like the outboard I have certainly does

Far out, but we're talking sterndrives here

No doubt the engine is smartcraft capable but again, OP hasn't revealed much info on the setup. Many smartcraft enabled engines were installed in boats that did not utilize smart guages.

Sea Ray has and still does manufacture boats with smart guages, vessel view, gps/Bluetooth, etc...but we know not of OP's configuration. Shall we entertain other ideas or wait for confirmation?

 

[QBhoy]

Never said it didn't

Far out, but we're talking sterndrives here

No doubt the engine is smartcraft capable but again, OP hasn't revealed much info on the setup. Many smartcraft enabled engines were installed in boats that did not utilize smart guages.

Sea Ray has and still does manufacture boats with smart guages, vessel view, gps/Bluetooth, etc...but we know not of OP's configuration. Shall we entertain other ideas or wait for confirmation?

Fair comment. Just thought I’d add my thoughts on it. May not even be relevant, but looks like the DTS was available for the bravo and mpi from 2005 onwards. Even if he doesn’t have the DTS, if I’m anything like close on this…I think there is still a chance his set up could have a rpm limiter when in a higher state of outdrive tilt.

 

[Egoodwin]

Update: I changed the fuel water separator filters 3 weeks ago w new WIX filters. I swapped them out today w mercuiser filters and the issue is gone. Boat revved to 4200 at about 30mph. I don’t know if the wiz filters got bogged w water as they were the first set of filters after winterization. Fuel tank sat almost empty 15-20 gallons for the winter. Maybe condensation inside the tank?

 

[alldodge]

You got water in there for sure, the filter tried its best to keep it out of the motor. Just more then it could take. Maybe after a bit of running drain the new filter to see if there is any more found