Help diagnosing continuous beep on start up 250proxs

[SlumpGumpy]

S/n: 1B964392 250ProXS
i’m not sure if this is all connected

Problem:
Occasionally when I start my boat the continuous beep occurs and I have no throttle
I can kill it/start it/kill it start it/wait a couple minutes and the beep will go away
sometimes along with the continuous beep the rpms will creep up a bit to 11/1200 (while in neutral)
this happens every outing over the last month or so
-I’ve got a good stream of water coming out
-I’ve got plenty of oil in the reservoir under the cowling/and the main oil tank

now I’m not sure if its related but I switched from a Duracell 31AGM to a Lithium Ionic 125AH this year
The continuous beep occurred last year a time or two with the AGM but I attributed it to sucking up some muck or something given the fishing circumstances

I also noticed with the 125AH that upon start up I get the “low voltage” alarm on my lowrance graph—something I never experienced with the AGM
*side note I have 2 buddies with the same setup that have never experienced this low voltage alarm

I’m looking at the Codes in the manual and I’m leaning towards the “BAttery Voltage out of limits” error but I’m not exactly sure what that entails

thanks for any input

[SlumpGumpy]

This may be my last fishing weekend coming up so I think I’m going to throw the AGM in the boat for just in case and maybe that will help me eliminate

[kllr bee]

Lithium batteries have way more violtage, like 14.6. That could be the issue.
Richard aka Kllr Bee

[Bob G.]

I would not continually ignore the beeping. If you sucked up muck through the cooling system, that also needs to be addressed. Get the codes read and fix accordingly. I wouldn’t run the engine until getting everything fixed.

[basshole51]

It is battery voltage related. Check your connections. are they clean, tight, free of corrosion/dirt/grim/etc ? You will be recommended a post like this -

[EuropeanAM]

Lithium batteries have way more violtage, like 14.6. That could be the issue.
Richard aka Kllr Bee

They do have a different voltage curve... but they're still classified as (and treated as) a 12V battery. Provided that the right battery was used.

As of this time, Mercury has not approved the use of Lithiums on the Optimax engine lineup.

That being said- your problem could be a throttle cable or hotfoot adjustment, a "happy foot" that stays on the throttle when starting (never do that), a bad TPS, or even an improperly wired 5V Sensor (such as a fuel/oil harness or sending unit). STRONGLY recommend that you get PRINTOUTS of the Run History, Freeze Frame (Fault) History, and the Fault Seconds Counters (G3 Diagnostic System, or perhaps Diacom).

[SlumpGumpy]

Thanks all!

[lpugh]

Verifie that the Battery is in fact a Cranking Battery

[JOE54]

^^^^^+1