The extra 30 pounds comes from having at extra cylinder (2 cylinders vs. 1) and a bigger head. Most manufacturers use the same engine block for an 8 and 9.9, so IMHO if you're going to get an 8 you might as well go for the 9.9 at the same weight (no need to crank it wide open, and you have an engine that could be even better if you up-size your dinghy in the future).Well folks I ended up buying a brand new 2021 Zodiac Cadet 270AL from Defender. It’s 8’ 10” with aluminum floor and 17” tubes. They were having a sale so I got it for $1385 which I thought was a good price for that model. It was one of the three original models I was considering.
Which now brings up another issue. The max rating for the engine for that model is 8hp but Zodiac recommends 6hp. I would like to get the 8hp and max it out because I always hear people say they wish they had gotten a bigger engine for their tender. There is about a 30 pound difference between those engines which can be an issue with taking off & putting on the engine solo. Also I believe the new 6hp engines include the internal gas tank whereas the new 8hp engines do not. It’s not a huge deal but certainly worth considering those little factors. Curious what y’all think
OTOH ~100# is a LOT of weight to heft on and off a dinghy. Unless you live in a gym, you're going to need a crane or a strong friend to mount and dismount it. (A crane if you do it from the mother boat). It's certainly not one-hander. That's also going to overpower a 270 cm dinghy and add too much weight in the back.
I'd get a slower, lighter motor, 30-35 pounds and call it a day. You'll envy people who plane their dinghies, but they're envy you when they see you one-hand on and off the stern rail, using a lifting harness. I downsized from a 9.8 to a Torqeedo. The 2.x HP Honda and Suzuki are also about 30 pounds.
PS - read other threads about ethanol and outboards.