100percentjake
New member
Hi all. Got a family heirloom Starcraft that has an '81 Johnson hanging off the back of it and I took a look at it this weekend and fixed a myriad of issues (battery cables, starter solenoid, incorrectly gapped plugs, intake plenum not properly affixed.
At the end of it the boat ran better than it has in decades for about 3 hours then became hard to start. I got it back to the dock and noticed that there was a massive amount of shaft play in the carb throttle blade shafts for both carbs, resulting in a large vacuum leak. This leak had also thrown off the sync of the carbs, so I pre-loaded the lower carb to bring it roughly back in sync with the upper and the engine would start, but idle at 1700RPM and was generally very unhappy.
These carbs seem to be a bit of a rarity, and don't appear to have any sort of distinct replaceable bushing for the shafts, leading me to believe my options are to either bore out the holes and machine some delrin bushings, buy another set of carbs and hope they are in better shape (haven't had much luck finding any) or buy the later style of 85+ carb with the adjustment screws in the throat, but then I'd have to get a new intake plenum as well which could prove difficult. Spraying carb cleaner on the throttle blade shafts with the engine running makes the RPMs jump significantly, so definitely a vacuum leak but I'm unsure if it is one that would affect runnability.
Anybody have some insight for me? This motor also appears to have two reeds stuck open on the bottom two cylinders, the coils are leaking potting compount, and it has NGK BH7S plugs which I believe aren't what are recommended. I have two weeks to get these carbs sorted before bringing them back down and putting them on the engine, so any help would be appreciated so I can get parts on the way.
Thanks for any advice.
At the end of it the boat ran better than it has in decades for about 3 hours then became hard to start. I got it back to the dock and noticed that there was a massive amount of shaft play in the carb throttle blade shafts for both carbs, resulting in a large vacuum leak. This leak had also thrown off the sync of the carbs, so I pre-loaded the lower carb to bring it roughly back in sync with the upper and the engine would start, but idle at 1700RPM and was generally very unhappy.
These carbs seem to be a bit of a rarity, and don't appear to have any sort of distinct replaceable bushing for the shafts, leading me to believe my options are to either bore out the holes and machine some delrin bushings, buy another set of carbs and hope they are in better shape (haven't had much luck finding any) or buy the later style of 85+ carb with the adjustment screws in the throat, but then I'd have to get a new intake plenum as well which could prove difficult. Spraying carb cleaner on the throttle blade shafts with the engine running makes the RPMs jump significantly, so definitely a vacuum leak but I'm unsure if it is one that would affect runnability.
Anybody have some insight for me? This motor also appears to have two reeds stuck open on the bottom two cylinders, the coils are leaking potting compount, and it has NGK BH7S plugs which I believe aren't what are recommended. I have two weeks to get these carbs sorted before bringing them back down and putting them on the engine, so any help would be appreciated so I can get parts on the way.
Thanks for any advice.