Gas motors are restricted here but the rivers and about five larger lakes allow gas motors with a couple lakes having a 10hp limit. Only one of them is anywhere near me.
The contamination warnings are a bigger deterrent to fresh water fishing than anything else here.
Common practice is to buy a 9.9hp and convert it to a 15hp, it then allows you to have a boat that will be able to move well enough to use in the limited lakes and one that can actually get away with some backwater and river use on a smaller boat. The river has no HP limit but the rivers are as contaminated as the lakes, if not more so.
Most rivers have fecal bacteria or chemical issues. Many small ponds are affected by serious algae growth problems stemming from fertilizer runoff, septic system leakage, or road runoff.
The lack of boaters on the rivers and lakes is a new thing, and this year has been worse than any years prior but its been slowly declining over the past 3 years with the last peak being around 2000 or so. After 9/11 things slowed down, then there was a huge decrease in boat registrations and boat traffic around 2008, it started to return to normal, or at least increase by 2019, then when everything was shut down in 2020, it never really recovered and although it got a little better at first, its been dying out ever since.
I read somewhere that the number of boat registrations overall is way down in the state, but its not just NJ.
The first big drop was when they required everyone to take a coast guard course for $110 to keep your boat license, about 1/4 of boaters just quit bothering. Another big hit to the totals was when the saltwater registry started and the threat of a saltwater license began, and now with the high cost of everything its eliminated even more.
Personally I quit fishing freshwater because of the cost of the license, and the fact that the fish aren't really anything I'd want to eat. I'm not paying $30/yr to fish for something I can't eat. The saltwater registry is free but saltwater is a 40 minute ride from where I'm at and the best fishing is in the ocean, not the rivers and I refuse to pay to park or launch my boat to access the back bays or inland boat ramps. I do most of my fishing these days from bridges and piers and my boat gets used mostly for crabbing.
The lack of interest in small outboards is not a lack of interest here, its a lack of money. There's plenty of folks who want them, but none who want them have money to buy them. Those who can afford them, buy new and don't care about the money issues. The few boats I do see out are generally all brand new or close to it. Older boats and motors have disappeared from the water lately.