Lake Grinnell (NJ): Motor and Boating Rules
Sussex County · near Sparta · managed by New Jersey State Police Marine Services Bureau
- Gas outboard YES
- Electric trolling YES
- PWC / jet ski NO
- Sussex County, NJ
- 40 hp cap
- New Jersey State Police Marine Services Bureau
Quick answer
Check your motor plate before hauling to Lake Grinnell: the limit is 40 hp. Lake Grinnell in NJ is limited to outboard motors of 40 horsepower or less under New Jersey State Police Marine Services Bureau regulations (verified July 26, 2026). Outboards rated above the cap are out. Electric trolling motors fit comfortably. Rules change and local ordinances may add restrictions — always confirm with New Jersey State Police Marine Services Bureau before you launch.
Rules at a glance
Plate rating counts — motors rated above 40 hp are over the cap even at idle.
What this means in practice
Why 9.9 hp motors exist: manufacturers build them precisely for lakes like Lake Grinnell, where a 10 hp cap is the line. If your plate is worn or missing, carry documentation — enforcement reads the rating, not your word for it.
The cap is about the motor, not your speed, on most waters: a 40 hp outboard at idle is still a 40 hp outboard. This lake has its own wrinkle worth knowing — see the note below.
Hours matter here too: the posted rule is "Waterskiing hours: weekdays 11:00 a.m.-6:00 p.m.; Saturdays, Sundays and holidays 10:00 a.m.-12:00 p.m. and 2:00-5:00 p.m. (N.J.A.C. 13:82-3.4(f))". Outside those hours, the stricter behavior applies — plan dawn and dusk trips around it on Lake Grinnell.
Worth knowing about Lake Grinnell: N.J.A.C. 13:82-3.4(h): vessels on Lake Grinnell shall not exceed 15 feet in length and shall not exceed 40 total horsepower. The rule also fixes a counterclockwise ski course with a two-boat limit and 65-foot maximum tow line; barefoot skiing, kite flying, para-sailing and ski jumping are prohibited..
Planning options around New Jersey? The neighboring pages in our database cover Grover's Mill Pond (HP limit, Mercer County) and Lake Marcia (No motors, Sussex County), and the state hub lists all verified New Jersey lake motor rules with the official source behind each.
Common mistakes on HP limit water
Rounding 9.9 up. A 9.9 hp motor is legal under a 10 hp cap — that is why it exists. Don't let a worn plate turn a legal motor into an argument; carry the manual or a photo.
Bringing the PWC. No production jet ski runs under a low horsepower cap, so the 40 hp limit on Lake Grinnell excludes them by arithmetic, no explicit ban needed.
Before you launch — verify
- The live rulebook is here: New Jersey State Police Marine Services Bureau
- For edge cases — mounted-but-unused motors, tournaments, temporary orders — phone the New Jersey State Police Marine Services Bureau office covering Sussex County.
- Our most recent source check for this page: .
Rules change and local ordinances may add restrictions — always confirm with New Jersey State Police Marine Services Bureau before you launch.
Frequently asked questions
Are gas motors allowed on Lake Grinnell?
Gas is fine here as long as the motor's plate reads 40 hp or less. Anything rated higher is outside the rule on Lake Grinnell. Verified July 26, 2026.
Can I use an electric trolling motor on Lake Grinnell?
You can. Electric propulsion is permitted on Lake Grinnell; most boats here run a 12 V transom-mount trolling motor. Pack a paddle as backup for when the battery fades.
Are jet skis (PWC) allowed on Lake Grinnell?
Jet skis are out on Lake Grinnell. No production PWC comes in under the 40 hp limit.
Who enforces boating rules on Lake Grinnell?
New Jersey State Police Marine Services Bureau (state department of natural resources) sets and enforces the motor rules on Lake Grinnell, with possible additional ordinances from Sussex County or local municipalities. State boating officers and local law enforcement both patrol restricted waters.
Where do I verify the current rules for Lake Grinnell?
Use the official document linked in the Sources section of this page — it is what this summary is based on — or go to New Jersey State Police Marine Services Bureau directly. We last verified this page against the source on July 26, 2026.