I must be missing something, you guys keep saying Watts, not Amps.
My old school math tells me that 3 Watts is less than 1/2 an amp, which is maybe a reasonable trickle charge for a snowmobile/motorcycle battery if it has ZERO draw on it, but seems to me to amount to almost nothing for a boat charge.
I would guess that most boats suffer greater than 3 Watts to parasitic loss from the various marine electronics that have functions always running in the background, let alone if you were running any device which would put you at a significant net loss.
I personally have never had a trickle charger that was smaller than 1 full Amp and many are variable power up to several Amps as required due to the constant drain by some devices.
I guess everyone's needs are different, but it doesn't seem reasonable that anything under 1 Amp capability is going to really do much for you.
Sometimes paying a few dollars more for a more robust capability is a far better long term investment.
So with that said, and getting back to the original question, I wholeheartedly endorse upgrading to the larger 27 series battery. I have done this in every boat I had with a 24 series battery and never regretted the extra expense as it bought me a lot of peace of mind knowing I had that extra capacity and I believe it also bought me additional longevity, so in the end I feel the cost balanced out.
ATB
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