How can I boost the performance of my Briggs and Stratton 5hp 4-cycle outboard motor?

Question

Already have a "performance" spark plug. Wondering how to safely up the hp. The warranty is up, so I don't care about voiding anything.

Answer 1

Another thing you could do, if you have the time and money, is port out and polish the intake . Readjusting the carb would follow.

Answer 2

how about Nitrous ?

Answer 3

Get rid of that "performance spark plug" All that will do is give you a little boost before it burns a hole thru the top if the piston. You didn't say how old it was, but get some preimun gas and some quality raceing oil for air cooled engines. Some of these had a fully adjustable carb. So get you idle adjusted so it starts hot every time then go out on smooth water. Adjust the main jet at 3/4 throttle till it peaks, then open it some more till you can just detect a drop in performance. Take the skeg off the lower unit and replace the white grease with something slipperier-black molly or slick 50 grease. Get good at it you will be doing this often.That's as good as they get. The best way to do better is get a bigger engine with a better reputation. (PS- they have a water pump-make sure it's working or the bottom bearing and seal go away.