Anyone else running a Victron Multiplus on a narrowboat with shore power hookups at marinas?

Been living aboard for two winters now and the Multiplus 12/3000/120 has been genuinely brilliant — handles the transition between shore power and inverter mode so smoothly I barely notice it. But I've started having a weird issue when I plug into some of the older marina hookups on the cut. The unit keeps throwing a low AC input voltage alarm and switching over to inverter mode, even when the shore power seems fine on my plug tester.

Wondering if it's the Multiplus being fussy about dirty or fluctuating grid power from ageing marina pedestals, or whether I need to tweak the AC input low threshold in VE.Configure. Currently set to the default 187V lower limit. I've read you can drop it further but I don't want to start pulling in genuinely dodgy power and stressing the battery bank — 200Ah of Fogstar Drift lithium that I'd rather not cook.

Has anyone had similar on a boat, or even in a shepherd's hut hooked up to a farm supply? Those rural single-phase feeds can be just as wobbly. Curious whether a voltage stabiliser upstream is even worth considering, or whether the Victron is actually protecting me from something real and I should just... trust it.

Not on a narrowboat myself — static caravan and cabin — but the seamless transfer on the Multiplus is something else isn't it. Same experience here when the grid dips or I'm switching sources, absolute zero noticeable crossover.

One thing worth flagging for marina hookups specifically: worth setting your shore input current limit conservatively. Some marina pedestals are genuinely flakey and can't deliver what they claim. Victron's PowerControl feature handles it well but you need to dial in realistic numbers or you'll be tripping the pedestal breaker constantly.

Also make sure your AC input assistant is configured properly in VE.Configure if you haven't already — makes a real difference in how it handles weak or fluctuating shore supplies.

Interesting thread — not on a narrowboat but running a Multiplus at my cabin and the seamless transfer is exactly what sold me on it too.

Quick question for @HazelDawn though: how are you finding the shore power input current limit when you're at marinas? I've read that some marina hookups are quite restricted — 6A or even less on older pedestals — and I'm wondering how the Multiplus handles that when your batteries also need charging simultaneously.

Reason I'm asking is I'm looking at adding EV charging to my cabin setup and the PowerAssist feature seems like it could be genuinely useful for managing limited incoming supply. Curious whether you've had it actually cut in during a restricted hookup, or whether marina supplies tend to be decent enough that it's not really needed day-to-day?

Really useful thread this. Running a Multiplus 12/3000/120 myself but in a tiny house setup rather than a boat — similar challenges though with variable shore power quality at different hookup points.

One thing worth mentioning: if you're not already using VE.Configure to set the shore current limit, it's worth doing. Some marina hookups are only rated to 10A or even 6A and the Multiplus will happily try to pull more if you let it. Set it conservatively and let the unit balance accordingly.

Also @HazelDawn — what's your battery bank? Curious whether you're on lithium or AGM for the winters. I found cold temps hit AGM capacity pretty hard. Swapped to Fogstar Drift cells last year and it made a noticeable difference for overnight loads.

Ran a Multiplus 12/3000/120 in my van for three years before moving it into the garden office, so I know that transfer switching well.

One thing worth knowing on marina hookups specifically — shore power quality varies wildly between marinas. Some older installations are genuinely rough. The Multiplus handles it, but I'd strongly suggest enabling the input voltage and frequency tolerances in VictronConnect if you haven't already. Narrowed mine down after noticing the unit falling back to inverter mode unnecessarily at one particular mooring.

Also worth checking your shore power lead's earth continuity regularly if you're on a steel hull — not strictly a Multiplus issue but it'll cause grief that looks like an inverter problem.

@HazelDawn what firmware version are you running? There were some noticeable improvements to transfer behaviour in later releases.

Been on a 57-footer for four years now with the same unit and I'd echo everything @HazelDawn says about the transfer. One thing worth mentioning that nobody's touched on yet — the PowerControl feature has been a godsend at marinas with stingy 16A hook-ups. Set the input current limit low enough and it'll top up from the batteries when demand spikes rather than tripping the marina's breaker. Saved me a few embarrassing moments running the kettle and microwave simultaneously! Worth having a play with that in VictronConnect if you haven't already. Also make sure your shore power lead polarity is correct at each new marina — I've come across a couple with wiring that's a bit... creative. The Multiplus handles it but it's not ideal.

Been on a 48-footer for three years with the same unit. One thing nobody's mentioned — the input current limiter is your best friend at marinas. Some of those 16A hook-ups are lying through their teeth, especially the older pontoons. Set it conservatively (I run mine at 10A) and let the Multiplus top up from the

Really glad this thread came up — been on my 62-footer for eighteen months with a Multiplus 2 (slight upgrade from the unit you lot are discussing) and one thing worth flagging is the PowerAssist feature when you're on a weak shore supply. Some of the older marina pedestals around the Midlands canals are genuinely terrible, and having the Multiplus supplement the mains with battery power when demand spikes has saved me from tripping the hookup more times than I can count. Definitely worth configuring properly in VEConfigure if you haven't already. @CotswoldNomad's point about the input limiter ties into this nicely.

Great thread — I've had the Multiplus 12/3000/120 on my 55-footer for about two years now and one thing worth flagging is how well it plays with VE.Bus Smart Dongle if you haven't already added one. Monitoring everything through the Victron Connect app while you're away from the boat gives real peace of mind — especially at unmanned marinas overnight. You can see exactly what's happening with your shore hookup remotely. @HazelDawn and @Finn1975 might already be across this, but for anyone newer to the system it's a relatively cheap addition that really unlocks the unit properly.

Really useful thread this. I've got the same unit on my 57-footer and one thing I'd add is keeping an eye on your shore power cable and connector condition at marinas. A dodgy 16A hookup plug can cause the Multiplus to hunt between shore and inverter mode repeatedly, which I initially thought was a settings issue. Took me ages to realise the marina's socket was the culprit. Worth carrying a spare quality 16A blue connector — I swapped mine out and the switching behaviour became rock solid. @HazelDawn sounds like yours is working a treat already though!

Really useful points all round. One thing I'd be curious about — has anyone actually measured the transfer time between shore and inverter mode with an oscilloscope or even just a UPS tester? The spec is around 20ms but I've seen reports of variation depending on AC input voltage quality, which matters if you're running anything sensitive.

Also, @RobRobinson78 — when you mention the shore power issue, are you using the input current limit feature in VictronConnect to throttle the charge rate at dodgy marina hookups? That's made a noticeable difference on my garden office setup with a weak grid feed.