All small gassers have aluminum cylinders, the head is part of the cylinder...
This one weighs 2 lbs 7 oz with a CM6 spark plug, Chinese ignition, no muffler...Almost exactly the same as a converted G26....If you do the work yourself you can save about $100 over the cost of a converted new G26.....Quality looks good, I have been told the Zenoah crank and cylinder is better in the long run....Zenoahs run up to 16,000 rpm in boats, don't know about CY cranks...
I think the QuickDraw water cooled boat engines run closer to 20,000 using Zenoah cranks...
Might be some information on Jim's Boat Dock website...