Welcome! Need support, you got it. Or share you ideas and experiences.
I just bought a Tohatsu 8hp 2 stroke. I plan on putting this on the back of my Scanoe (flat bottomed square sterned canoe). I replaced it with a Nissan 4hp 4 stroke. The 8 and the 4 weighed the same. I don't know how much more speed I'll get out of this change, but it might be scary. Anyways, my boat is rated for a 5hp. Is this something water patrol will look for?
Spacelad, never mind the patrol, overpowering your boat is a bad idea. Your scanoe is rated at 5 hp because any more will make it dangerously unstable, especially in turns. And you will not see much increase in speed, as a scanoe will not plane properly, no matter what power you put on it.
I had to buy the 8hp because I couldn't pass up the deal. When using my 4hp It just seemed there was a lot of potential speed I was missing out on with this boat. The bottom of this boat is flat, just like a Jon (but in a different shape of course). I can't grasp as to why an 8hp wouldn't dramatically increase speed on a 110lbs boat properly weighted. The 5hp limit on this boat is because of the engine weight. Th Tohatsu 8hp engine is 57lbs, exactly what 5hp would weigh. The 4hp pushes me 8-10mph and I would expect the 8 to push me 15mph. I am really into the 8hp because it DO NOT have the internal fuel tank.
Who told you that the hp limitation had to do with engine weight? Was it the guy who sold you an 8 horse motor for a 5 horse boat? LOL.
The concern is safety. Hp limits are pretty well thought through by the US Coast Guard. And motor weights have nothing to do with it. The thrust of a higher hp motor can overwelm the stability of a boat. At the very least you will get wet, maybe seriously hurt.
And too much horsepower is not just dangerous, but wasteful. Higher displacement motors burn more fuel, even at rest.
That said, you may be fine. I suppose there may be models of scanoe that I've not seen, maybe wider and more stable. The ones I have seen were not true planing hulls. Not for nothing. Just out of curiousity, what is your transom width?
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