I think a 9.8 might be a bit "lean" for that, although I Hear You about
the size. Here, "under 10hp" means you don't have to license it. Then
again, there's lots of 15hp engines around with 9.9 "tags" on them...

I forgot to respond to this in my last post. The 10hp limit has nothing
to do with license. Here in New Jersey, many lakes in state parks only
allow a boat that is electric only or has a small gas engine that
doesn't go beyond 10hp. If the gas engine in a boat is over 10hp, we
cannot run the boat in that lake. This significantly limits the number
of freshwater lakes that I can run the boat on (something like from 10
available lakes reduced to only 2). And two of the lakes that I really
want to fish have that 10-hp limit. If I want to use a large engine, I
will have to use it in sal****er or those two freshwater lakes
mentioned above.

Currently, my primary plan is to run the boat on freshwater lakes.
Running the boat in sal****er is only an afterthought ("that would be
nice" kind of thing). Therefore, outfitting the boat with a gas engine
that can run in most of the freshwater lakes is the first priority. And
I am glad to hear that a 7.5hp gas engine should be fine for a 18-ft
boat with 4 adult males on it as long as I am OK with running the boat
in displacement speed.

Two years from now, I may have explored enough of the freshwater lakes,
and I may start thinking of running the boat in sal****er. At that
time, I may decide to get a 25-hp or 40-hp outboard motor, and use the
7.5hp engine for trolling.

You have helped me to make the right selection. Thanks.

Jay Chan