Aluminum boat? There is no way I'd allow a wet lead acid battery on my aluminum boat.
never had a problem in any boat or other rigs,but I do take care of my stuff...
Then the Duracell SLI24MDC is a good, cheap, wet acid, marine deep cycle. It’s a group 24, 75ah. They are about 45lbs and run around $110 each. I believe Walmart carries them. They should last you 4 or 5 years if you treat them right. I have a set in my RV and they have served me well.
Next step up, I also own a set of SLI31AGM – Group 31, 100ah. They weight about 65lbs and go for about $250. Very good batteries and being AGM, you don’t have the acid spillage issue to worry about or contain.
The very best lead acid deep cycle I’ve ever owned is the GC2-XHD-UTL. I run my cabin on a pair of them, they are 7 years old and are just now starting to show their age. 232ah and they weigh a ton. I think they were somewhere around $200/each. But they are 6V so you would need 4 of them. Weight and volume probably make them impractical for a small boat.
Whatever you pick, you are going to get stuck with core charges unless you have a trade in. I think they run about $40 per battery.