I think the 9.9 might be / is a looper.----And it will run at 90 PSI.-----Remove bypass covers and inspect pistons / rings.----Easy and no parts needed to do that.
Many 25" motors available.-----Location is everything.----Know of a 25" 8 HP now used on a 19' boat with great success.----Extension kits may be available.----New motors use up a lot of beer tokens.