I am planing on getting some new lipos for my SV27 i was wondering if these battery links i am posting will fit first of all and which one would be best i am deciding between these 3http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=14072http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=20680http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=17269I am planing on buying them soon so any advice would be greatly appreciated.

I'd recommend not going with hardcase packs in boats. There isn't any air circulation inside the boat and hardcases tend to run slightly hotter inside a boat due to that. Also the 4mm plugs that are imbedded inside the battery are going to be the week part of that battery. Look up the turnigy 2s 5000mah 40c packs. The usa warehouse might have them. Cheaper and will perform very well in the SV. JMHO!

http://www.hobbyking.com/hobbyking/s...arehouse_.html

* Remember to grab a lipo shield for your SV as the stock esc is not lipo ready.

What about the zippy they say 8400 mah that would be really long run times is it worth it?

I don't think it's worth it. The extra weight in the hull and more importantly extended runtime isn't always good in boating. The electronics are abused much more then in land and air vehicles and the results is more heat. With a mild prop such as a graupner CF42 and those 5000mah turnigy packs you should see 4 or 5 minutes of good solid runtime.  I think that's plenty of runtime. Just remember to drive properly (constant wide open throttle, and long straights) and allow cooling in between battery packs.