Curious, how does your cavitation plate line up with the bottom of your boat? Even, above or below?
Thanks for the pics, that helps a lot. I have a pretty basic Alumacraft 1648 flatbottom and an old 9.9hp Evinrude 2-stroke would push it about 15 mph with just me. It hardly drafts any water so it's very easy to get up on plane which helps a lot. I think I was using the factory 10" pitch prop at that point. With exact same boat setup and a 15hp with a 4 blade 9" pitch prop I was doing about 20mph. I think it's safe to say your boat is heavier than mine plus your hull design may be a little tougher to plane out (I dont know - not much experience with vhulls). If you have 10hp restrictions I think you would need to swap to a 9.9 2 stroke that can be converted to a 15hp like the Johnson/Evinrudes or the Nissan/Tohatsus. Ive heard you can put an 18hp powerhead onto the 9.9hp Nissan models. It's def skirting the rules but its still not going to make your rig a speed demon and in reality you will make less wake and burn less fuel that way which is better for the lake.
just about perfect, i stopped at a marine yesterday and did inquire about a prop and a hydrofoil, the employee came out and looked at the set up and said the boat is a deep and heavy hull, the 9.9 even with it propped and a hydrofoil will probably never get the boat on plane, so that's that, going to sell the motor or the boat. and get something to work
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If your boat is the one I'm thinking of, with full flooring and high freeboard, it weighs near 400 lb dry. Add rigging, battery (batteries?), trolling motor, tank of gas, your gear, and a couple of passengers and you're asking a lot for a 10hp class motor to get it up on plane.
I had an even heavier SmokerCraft 14' years ago, with a 25hp Johnson it flew. If you had problems getting your boat on plane with a 25, something wasn't right. If you're porpoising you have the wrong tilt setting for your weight distribution, or you're seriously stern-heavy.
With the 9.9 the fin might help you get a higher top speed while keeping the bow down, even if you can get up on plane. Good advice above on prop selection too. You might need a lower pitch prop to get the most out of the small engine. You want a prop that give the highest top speed with the engine in its standard top rpm range.
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Just for comparison. I have a 1648 Jon with a ‘74 Evinrude 15 and no fin. It almost gets on plane but not quite and runs about 14 mph with me and 11 or 12 with a passenger. I don’t think that the 10 four stroke will plane it, no matter what. If it was bare bones with no gear and just you it would improve some but I don’t think it will do what you want. I came out of a bass boat with a 150 so this small boat is a change for me but the lack of speed doesn’t bother me at all. It is just my mindset, this is what I’ve wanted for near four years and it does what I ask very well, and it’s paid for. Sorry to hear that your plans aren’t fitting the bill that you were after. Another thought is to keep the motor and get a smaller boat for the low hp lakes. Not what you planned but it’s an option. If you really want to get crazy, look into an electric motor to push the big boat. It’s pricey and I don’t know if the restrictions would let you but they’re making electric outboards up to 50 hp. Maybe bigger. Good luck with it all, hope you find what you need.
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