carb settings

[jackmcl123]

have scott atwater 5 hp.need the carb setting the carb is tillotsion md 74A .thanks in advANCE

[frankr]

About a turn out from lightly seated on the high speed, and 3/4 turn on the slow speed will get it running. From there you need to fine tune it in gear, on a boat, on the lake. Be aware that the slow speed needle works "backwards". That is, turning it in makes it richer, just the opposite of what is normal.

[jackmcl123]

what do you look for in gear on lake as per settings. by slow speed do you mean idle

[frankr]

The process is run it at full throttle in gear, and adjust the main (high speed ) needle. Slowly turn it to the right till it starts to lose power, then quickly turn it back to the left till it regains power. That is the optimum setting. Slow down to as slow as you can keep it running and do the same with the slow speed (idle) needle, except as I mentioned it works backward. So turn it to the left till it loses power (may sneeze or stop), then turn it back to the right till it runs smoothly without sneezing or stalling.

Double check your work by repeating the procedure. Then you don’t have to monkey with them again unless a big change in temperature, or altitude, etc.

[jeff-register]

Also to add to Franks settings. Once you get it running very well time to adjust the idle screw again. At idle in gear very slowly loosen
the idle mixture jet until it runs very smoothly. That is a great setting for trolling as it will run very smooth. Before taking off fast turn the jet 1/4 turn out, to adjust the air flow. Remember like Frank said you do not adjust the fuel but you vary the air ratio.
These are good little motors except the gears are very hard to seal up. check the flatness of the 3 screws with a straight edge as the threads pull out a tiny amount & cause leakage. Another spot is the driveshaft. Usually the shaft is pitted from rust. The area in the case can be drilled out to accept two drive shaft seals. The lower shaft seal keeps the oil inside the case aimed down. Next the top seal is aimed up to help keep the water out. Going backwards to the impeller housing when you want to get it out to get at the seal you must heat the impeller housing as it is glued in. Once it gets hot it will release. Be careful not to bend it. Under that is a O-ring too above the impeller housing top cover. Have fun with your motor. I still have my 7.5 hp
ScottAtwater (Firestone) for 35 to forty years now.
Enjoy,
Jeff

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