I have a 67 Johnson Seahorse, Model# CD-24D, mounted on a 64 Starcraft 12' Aluminum boat. It seems to run and idle fine, usually starts with one or two pulls. But at WOT it seems sluggish, won't even plane the boat off. It will really rev up in nuetral, but in gear it just seems doggish. If I have someone else in the boat with me it's even slower. Any one have any ideas?