why do the xp3000's say designed strictly for supplemental use and don't even list cranking amps. they have separate categories on their page. starting batteries and secondary batteries. on a smaller boat with two batteries do you need one for each and change the battery switch for what you are doing or what?

Best practice to use the same brand, age and size of battery in a bank. Example put the "Start" battery on engine 1. Stereo batteries on engine 2. All stereo batteries should be the same. Caution, with more than 3 full size batteries depleted, a 100amp alt will struggle, especially if idling much since the alt is probably putting out a quarter to third of its rating.
IF the stereo batteries are dead, that is when engine 2 switch can be changed to start off engine 1 battery then moved to 2 once started (in most cases. Use caution when changing the switch to not go all the way to OFF, that is when alt damage can occur)

I can assure you, there is no problem starting with multiple performance batteries. In fact, I bet you will LOVE it. Engine will turn over much faster with the greater amperage. I run two Optima blue 27s on one bank and 3 Kinetik 2400s on a separate bank. Old, cold, 454 spins like a 4 cylinder. Down side, if you can call it that, is you will not realize a starter is going bad until its real bad because the higher amperage can spin a very corroded armature.

Just bought two new mini starters also. Never used them in anything yet however looking forward to seeing how they function.

Btw do you have dimensions of those batteries by chance? The optima blue 27's.
Tks for the feed back.
John

I would not recommend Optima today unless you really crush waves hard. Vibration protection is their only benefit. They are not as good as they once were either in general quality or in relation to other products on the market, IMO. General large deep cycles like Interstate or Deka would be better choices on the basic side with performance batteries like Kinetik and XP on the higher side which are also able to address the vibration issue to most degrees.

Specs from website - http://d26maze4pb6to3.cloudfront.net...pecs_Sheet.pdf
As long as extreme vibration is not an issue, using a charger to full charge and maintain batteries as well as not running them down are the two best practices to long battery life. My optima are 9 years old and Kinetik 5 years old. All still tested close to spec last summer, have not had them out this year.

Another vote for Kinetik. I'm running a few of them that Waves&Wheels installed when they installed my whole new system. I can run 6+hrs at 90+db no problem.

That's good to know. I've also got several muscle cars I should consider the same for as well as keep them on those on demand trickle chargers. Due to very little use batteries never seem to last as they should however it's my fault. Just to any other things always going on.

For my stereo setup I use 2 Deka Group 31 house batteries wired parallel as a single bank. They are used for the stereo only. I have two separate batteries for cranking. The house batteries stay isolated from the rest of the electrical system (meaning they get used for stereo and do not get charged via the alternators). However, I can flip a switch to merge them into the whole electrical system if needed (if cranking batteries are dead for some reason). I have a 30 AMP charger that charges things up when at the docks/rack/trailer/etc. In my previous boat, I accidentally left the battery switch on all and started up the boat and ran home. The House batteries were pretty low (I had a similar set up). The strain form the house battery bank was too much for my alternator........ Since then I make sure the house batteries are isolated. A large deep cycle is tuff for an alternator to keep up with, then add two into the mix. Even if it didn't damage the alternator, you would have to run your engine for a long time in order to charge a bank of deep cycles.. I use Deka only because I have had really good luck with them. I abuse the hell out of them and they just keep going. I have heard good thinks about Kenitic as well, but they are a little more expensive when comparing similar batteries.