When we were racing the Extreme, we ran with a DMS technologies sealed battery, tiny thing, about the size of a motorcycle battery! never a problem starting, or running the 8.2 litre EFI mercruiser, and so small & light, it was easy to mount, didn't try to beat the boat, or battery location to bits, and generaly 'the way to go'. not cheap mind!
Here's their website.
http://www.dmstech.co.uk/varleyredtop.htm
If you're momentarily losing electrical power, which is causing problems, fix the feckin momentary fault!