Heads up:

Its Princess Auto, no sweat on the typo YHR. I've been trying to get some of their 750 motors for my Bruiser gearbox. May have to get 'em off eBay (taterbug39)

You sure they aren't gelcells YHR? Personally, I'd never put lead-acids in my tanks. A gel-cell, yea, NiCd, NiMh, or Li-Ion, sure... but never a lead acid. Why? Acid leakage. If it leaks, that acid will ruin your styrene casing. I put 3 layers of nitro-proof epoxy in my 52" boat before I dared run the lead acid motorcycle batteries in her, because I knew if they leaked, they'd ruin the wood. Luckily, I never had a leak, and used the batteries til they wouldn't take a charge any more. an acid leak is as bad as the non-styrene-safe lube on the Pershing tires warning we had a while back (it made the bearing sockets crumble)

I have a local store called Total Battery where I can get custom packs built, zap-assembled for a buck a cell, covering included (double the thickness of standard NiCd cell packs) and I supply the connectors. I had 'em build packs from old laptop batteries I had recovered (they were dumpster bait) and the four 10-cell packs went with my Graupner Portofino. Running her on a pair while the other pair charged, she went like a bat outa h*ll with her strudder outdrives.

JMHO.