Performance Boat Shop

Exceeding your boats maximum horse power rating?

I have a jon boat made of fiberglass and wood. The maximum hp rating is 30hp but i recently got a 40hp given to me. I can add to the rear transom with epoxy and wood and im fairly confident i can renforce the the transom alot. I also recently added a 100 pound platfourm to the bow. I was wondering if i can put the motor that is 10hp more than the rating if i renforce the rear transom. Now i know that i can always put a throtle stop on the motor but i was hoping to keep it at full power, with out breaking my boat.

Public Comments

1. the biggest problem is getting stopped by the water patrol. most boats can handle a bigger engine, but the manufactures don't want to take the risk. if you feel you want to take the risk find a cowl for a 30 horse and put it on your 40 horse. of course you would be illegal still but not "obviously" illegal.
2. It's not just a matter of horsepower, it's also a factor of hull speed, which is a function of your noat's hull shape and design. I'm not saying you won't get more speed, but if you do, you are risking damage to the vessel itself, from a structural integrity standpoint. If the hull is not designed to take anything over, say, 10 knots, then making it go faster through the water creates stress on the hull that the boat was not designed for.
3. A boat traveling faster than designed will slide on sharp turns till the speed slows to a point that the hull will again grip the water. It's sorta like Hydro-planing in a car going to fast for wet conditions. Not to mention structural questions as previously stated. Good luck
4. Yes! As long as you are confident with the transoms strength you will be fine. Hull speed is not a concern due to the fact that the john boat is flat bottomed. Don't be concerned with the coast guard or local legal issues either. Really, your only concern is insurance, and what they don't know wont hurt em. If you're really worried just take the 40 hp stickers off the outboard.