Hi, I've got a beavertail 6.5 longtail. Has anyone replaced the 6.5 with something larger ( 9-10 HP)? It's an Alumacraft 1436LT it's going on. I need to stay below 10hp for hunt area regs. I guess the real question should be 'is the extra HP worth the extra time and money'. Any ideas will be appreciated.

You can gain a little with a 9-10 hp motor, but hardly noticeable.

To get the new motor on the frame, the easiest way is a motor that has the same PTO height and crank diameter, length, and keyway.

Another option is engine mods.
Go look on some kart racing sites, they take the 6.5 engines and very easily get a reliable 10 hp for less than the price of a new engine.
A new air filter, re-jetted carb, gutted exhaust and possibly some mild head work (valves lapped in, polished intake, and exhaust ports)

Thanks, I may try a few go cart tricks for the engine. AGK seems to have plenty of ideas. I'm new to the whole mud motor thing. I have been borrowing my dad's airboat which he graciously let's me use. But try hiding the thing. Thanks again.

hey its a little different but i did the same thing backwards i took a 29 hp mud buddy frame and swapped a 13 HP it took a lot of modifying but it was done fairly easy with a welder and a grinder so if ya do wind up having questions i can try and help

You can buy aftermarket performance parts for that 6.5 to gain hp. Look on any gokart racing site for this, they have tutorials on youtube, also on how to do these performance mods, also how to on removing governors. affordablegokarts.com is a good start

Go to Briggs and strattion racing and look at the animal motor