I just replaced the impellers on both of my motors,a 1991 88spl and a 1985 9.9 rope,long shaft.Let's start with the 88spl.Running on muffs it has good spray at telltale but after warmup,starboard side head cover is noticeably hotter than port,about 1.5 seconds on the 3 second hot finger test I've picked up in this forum.Port side is warm to the touch,just fine I believe.Now to the 9.9hp,have telltale on muffs,but not a high volume.When I replaced water pump,I hooked up hose to water tube and poked and sprayed compressed air till i had a solid stream.Motor is running hot also(a 1 second finger).Never had an overheating issue with either motor before,but am trying to do preventive maintenance.Could it be due to running on muffs and not in tank?Replacing thermostats is a good place to start?