RE "I would use brushless, but avoid Lipos in less there was a good reason for them.
Quite true Doug, I still have the first Zippy Flightmax 5s 20c LiPo I bought (02.06.2010) and it still balances after all this time, (just pulled it out of the archive and it's reading 3.92-3.91- 3.92-3.90.3.92 in storage mode) Doesn't have much guts any more but is perfectly usable in a boat. I have a few newer 4s 40c
discharge batteries
which have puffed/gassed, but are still usable with care ( don't suck more than 40A for too long, cool them straight away - always have an Esky with bagged ice handy if running batteries at high drain and getting them hot)
At home and you're testing, if they get quite hot, just put them in the fridge to cool down. I have even forgotten and frozen them solid in the freezer, (takes a while to get power back while they warm up,- bit like frozen frogs!) If you have any that puff badly or get very hot constantly for no reason, ditch them.
Safest way to do this is to make up a bucket of very salty water outside and drop the battery in to discharge it (you will see the leads bubbling,) next day, (if all activity has stopped), take it out in the middle of the garden (making sure the wind is blowing towards open space- Not your neighbors just in case as if it does smoke,- it's nasty stuff!) and ram a large garden fork or 4"nail right through it to make sure all the charge has gone and it's safe to dispose of (I still leave them outside in a tin for a few months just to be extra sure)
Do Not Do This Without Discharging In The Bucket First !!! as once they start you can't put them out, as it's a chemical reaction, and you will have so much nasty smoke you won't believe it !!!), not to mention a few thousand degrees of heat and flames!.
Now go out and buy a new battery and look after it properly ie, using correct charging, discharging and storage charging, and it should last for years, - especially in boats, as unless used in racing boats, the discharge for the average brushed/ brushless scale boat is nothing compared to planes.
JB