Carb conversion

[dphipps]

I've got an old K&B .21 outboard with an exhaust throttle, and it just seems like a finnicky setup to me. I would like to know if anyone has seen or done a carb conversion on one, or if it is even possible?

[BoatDoc]

exhaust throttles are finicky and can be a pain the arse. the engines are originally set up with standard carbs, you have to modify it to put the exhaust throttle on. which means that a standard carb works. if you want to switch back, we can help you do it, as it's not too hard. if you have trouble finding parts, let me know, i've got a whole engine and some spare parts that i'm not using anymore.

[dphipps]

exhaust throttles are finicky and can be a pain the arse. the engines are originally set up with standard carbs, you have to modify it to put the exhaust throttle on. which means that a standard carb works. if you want to switch back, we can help you do it, as it's not too hard. if you have trouble finding parts, let me know, i've got a whole engine and some spare parts that i'm not using anymore.

It's good to know that it can be changed to an easier setup. From what I can remember it sure seemed to rev up really fast with the exhaust throttle, but I could never really get a linkage setup that worked good. It also didn't really idle down much either, making trips to shore a bit hard. Now I don't know if thats how the exhaust throttle ones are or my lack of tuning/boat knowledge was the culprit.

I have found a picture of one just like mine.

http://devin.moonside.org/misc/oscar_becker9.jpg

So what would I need for a carb? And would I have to plug off the part of the exhaust where the plate was?

[BoatDoc]

k&b makes 3 types of carbs: black, gold, red. black is the smallest throat dia. red is the largest. i've run black and gold carbs, they arent' too difficult to tune. i've heard that the red ones are harder to get into the sweet spot. you'll need an exhaust adapter (p/n 30-8904) to go back to the standard set up.

[dphipps]

k&b makes 3 types of carbs: black, gold, red. black is the smallest throat dia. red is the largest. i've run black and gold carbs, they arent' too difficult to tune. i've heard that the red ones are harder to get into the sweet spot. you'll need an exhaust adapter (p/n 30-8904) to go back to the standard set up.

Thanks for the info! Which carb would you suggest I get?


I think 'restoring' this boat will be a good winter project.

[BoatDoc]

either the black or the gold carb will suit you well. if you plan on tinkering over winter, i'd suggest you go ahead and put in new bearings and gaskets into the motor. you might also want to inspect the piston/sleeve assembly and see if it needs to be replaced as well. if i recall, a piston/sleeve is around $60, and the bearings and gaskets add up to about $45. i may be off a little. you can download a parts breakdown and price sheet from K&b's wed site, it makes the process a lot easier. an extra drive shaft, prop nuts, and teflon in the tool box don't hurt either :wave: