My flatbottom has a 1968 Johnson 9.5 horse on it. When it's in the water and you turn it to full throttle it'll just idle. Sometimes you can put it in neutral and it will rev appropriately and sometimes it won't. As a test, I put it in gear and it did it's typical idle thing at full throttle. I left it running and pulled it out of the water, put it in gear and revved it and it revved appropriately. So I guess either water is screwing something up, or it can't pull itself when it's under a load. But, half the time in the water it will just idle in neutral as well when you rev it to full throttle.
I have been through everything in the motor. It fires appropriately, looks like the points are set appropriately (I took it to someone and had those set to double check myself), plugs are new and fire appropriately, so I guess it's a fuel issue. But, it appears to be getting gas fine in the carb. Ran a can of sea foam through it with no results. Any ideas?