Increase the hp of an 89 model 8hp Mercury

Looking at the parts catalog, it appears that the 6hp, 8hp, and 9.9 have the same piston/crank and most other parts. There are multiple carbs listed but all of them have four different jet sizes listed for the same jet, so I'm assuming that the jet size is part of or possibly the only change needed to control the hp rating of the engine. Can anyone out there with personal experience shed some light on this one. As mentioned in the title, it's a 1989 8hp mercury 2 stroke.

exhaust tuner is the big part of the hp , plus the carb throat size .

When I created the Frankenstein 8hp , found out all the carbs and all other parts were the same on the 6 thru 8 hp. So I got 6 hp carb, a rebuild kit and jet for an 8 hp. To brag a bit it runs like a champ and starts on the 2nd pull. This is was originally 1983 Evinrude 7.5 that was sunk in salt water for about 4 or 5 days.

After looking at the parts for 8 merc and the 9.9, it looks like you can just replace the jet in the carb.