I have a 1990 25hp Johnson outboard motor and the only way I get it started after it's been sitting for awhile is by spraying starting fluid in the carb. Once it has run for awhile I can start it with no problem. I checked the manual primer and it seems to be working ok. Once it's running I get a little back fire through the lower unit, but that may be just an idle speed adjustment. Any ideas would be greatly appreciated.