I have a 70 hp 1985 70 hp Nissan outboard. Took out this weekend to see how she ran and it did fine until full throttle. After about 15-30 seconds full throttle it falls on its face/bogs down and will die unless I back off throttle and give it a few seconds. Seems like possibly carb isn't keeping up with fuel demand for some reason. Recently took carbs apart and cleaned them, as there was some old residue clogging the lower carb. Floats appeared to be in good order. No carb rebuild kits available for this motor but some of the carb parts are available individually. Not even sure it is carbs but that is just my guess. Any thoughts on this one guys?