Tuning your Nitro or Gas engine takes patience!
 
STEP #1: Begin by setting your engines mixture at the manufacturers spec. (check it, don't guess). This is usually 3-1/2 turns out on the Needle and 1 turn out on the air screw. If anything run your engine to RICH! It will run but "blubber" or sound "muddy" this is a good SAFE starting point. (TERMS: "out" means counter clockwise).

PRECAUTION #1: If it runs LEAN it could seize at high RPM! Remember, if you lean out (turn the screw in, or clockwise) the air screw you must go richer (turn out, counter clockwise) the needle screw! If you don't you are leaning the entire engine which can damage or seize the engine!

STEP #2: Start the engine. Your engine should gain RPM nicely with a QUICK grab (less than 1 second) of the throttle (at the radio) and return to idle smoothly and quickly. If it sounds OK (crisp & snappy), get it in the water. No more adjustments can be made until water cooling has stabilized the engine's operating temperature as the boat is run. The heat generated from the engine will start changing the performance and require mixture adjustment of the carburetor (EVERY TIME you run the boat!). Nitro engines will require more adjustments more often than Gas engines like the Zenoah.

PRECAUTION #2: Running of the boat out of the water for more than about 30 seconds can damage or seize the engine!

STEP #3: Now carefully, bring the boat back to you (at the shore) and adjust the engine for better top end RPM. Remember the peak RPM only counts if the boat is in the water. So make the adjustment and send the boat back out for another pass. Repeat this process until you feel your engine is achieving it's peak RPM and check the boats engine temp often. You should be able to touch the engines head for a second. If it is scalding hot, Richen it back up!!! 

PRECAUTION #3: Running an engine LEAN is THE quickest way to destroy an engine!

If it dies: typically the engine is to lean (rich engines do not normally just stop running). Note the throttle position when the engine dies. This determines if you adjust the Idle (low end), Air Screw (middle) or Needle (top end).

If it is "muddy": typically this means the engine is too rich. If the engine is pretty "snappy" off of idle then lean the Needle (or top end clockwise) a few clicks at a time. If the throttle response is muddy all the way through, then turn the air screw clockwise ONE click at a time. This adjustment is very sensitive! This leans the bottom and top end at the same time.

If it smokes: It's running hot and maybe to lean. Richen it up (needle counter clockwise) until it starts to run a little muddy again. Once muddy go 

If you make ANY of the following changes to your boat, richen the mixture and start from the beginning to make sure the engine is not run to lean.
Things that change the tuning:
1) Prop pitch (richen top end to start)
2) Pipe length and type (affects the top end the most)
3) Nitro level (usually requires changes to air screw and needle)
4) Temperature (warmer air more fuel) more info
5) Humidity
6) Altitude (less air means less fuel is required)
7) Chips or Scratches in the bottom of the Hull (creates more drag)

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A FunRCBoats reader's tip on tuning

Still have questions? Contact us, maybe we can help.

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