Hi Lads,
Many thanks for advice,think Iwill disconnect ESC just to be on the safe side
Regards
JOE

Hi Joe
I would not have the ESC and charger attached at the same time.
You could use a heavy duty double pole two way switch or just unplug the ESC and plug in the charger, best option in my opinion.
Mains chargers for SLA batteries will limit the voltage and current but they are susceptible to transient surges from the mains which could produce a similar surge to the ESC if connected.
You should also be aware that Lead Acid batteries (includuing SLAs) can in certain circumstances give off highly explosive gas and in an enclosed space any spark could result in a big bang that would not be good for the model or anyone in close proximity.
If you really have to charge in the boat make sure there is plenty of air space and take care when attaching and removing the leads. This applies to the charger and the ESC leads...
Take care
Dave

Hi I have two boats both with 12 v 7 AH both battery's charged in side boats. Maintenance done twice a year removable on battery's and motors etc
Never had a problem as yet with ESC or anything else