Actually, I am thinking of 9.8hp because many lakes in New Jersey
(where I live) have restriction to limit the engine to no more than
10-hp. And a 9.8hp 4-stroke engine is around 90-lb; two persons with a
carrier should be able to hoist it. I am currently leaning toward
getting a 9.8hp as long as it can push the 18-ft boat with 4 adult
males on it at 10 to 15 land-miles per hour. What do you think?

You are going to need at least a 15 to do what you intend to do, but I
believe that a 25 is going to be much more appropriate.

This is kind of disapponting to know this; I am hoping that a 9.8hp
will be good enough. Seem like I will need a 25hp outboard gas engine.
In this case, I need to get a very powerful electric trolling motor for
lakes that are electric only or limit to 10hp-or-less. Luckily, those
lakes that have restriction tend to be small lakes (with some
exceptions).

Oh well...

Thanks anyway.

Jay Chan