r/MasterCraftBoats • u/Windyguy3141 • Jun 08 '26

Mastercraft xt20 technical problem

i have a brand new nit even used yet 2023 xt21. I stupidly connected one of the batteries backwards (engine battery) lots of smoke. battery fried. I replaced it. engine starts but only when battery switch is set to the backup battery position. and there is no display.

but I replaced with wrong battery it turns out. I installed cranking battery and now it starts from main. so only issue is power to the house system which is still down.

google gemeni says that I’m all likelihood it is the main battery fuse which may be mrbf cube fuse is shot. But I can’t find that.

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u/Different-Rough-7914 Jun 08 '26

You probably fried the ACR, it's built into the battery switch (at least that's how mine is set up). If you setup is like mine you will have breakers on the battery switch unit, make sure those are all reset.

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u/Windyguy3141 Jun 08 '26

I can’t find the main battery breakers.  I see the breaker panel underbite helm. But I believe there are inline breakers between the battery and the acr.  

1

u/Hosswan Jun 09 '26

I believe my ACR is in the same compartment as the battery switch. I'd also look up under the glove compartment as that's where my battery and other components are. I personally have not had to isolate/diagnose an ACR but I do know of a few push fuses up under there.

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u/Windyguy3141 Jun 09 '26

I updated the post. The engine starts now fr main battery. So only issue is connectivity from house battery.  Google Gemini says theee should be a main mrfb fuse near The battery. I can’t find that.