(Carburetor Adjustments - Two Adjustable N/Vs)
(J. Reeves)
Initial settings are: Bottom high speed = seat gently (turn needle clockwise), then open 1 turn out(counter clockwise). Top slow speed = seat gently(turn needle clockwise), then open 1-1/2 turns out (counter clockwise.
Once you have adjusted the idle/slow speed needle and the high speed needles, then snug up/ tighten part numbers 83 and 89 with 7/16 open in wrench enough to feel resistance when you turn the needles, but not too much where it makes it very difficult to turn the needles by hand.
Setting the high and low needle valves properly:
NOTE: These settings should be done a large test barrel or on the boat in the water/lake!! It best to do these adjustment on the boat in the lake or on commercial size test tank. (You can damage your motor running it wide open in a small test barrel.)
(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn in (clockwise), waiting for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out (counter clockwise) the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting.
(Low Speed) Slow the engine down to where it just stays running. Shift into neutral. Again in segments of 1/8 turn in (clockwise), start to turn the top needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running. Eventually you'll hit the point where the engine wants to die out or it will spit back. Again, at that point, back out the valve 1/4 turn (counter clockwise). Within that 1/4 turn, you'll find the smoothest slow speed setting.
When you have finished the above adjustments, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.