How to Correctly and Efficiently use an Onboard Mixture Control

Marty Davis

I have been asked hundreds of times how to use a mixture control. I have finally gotten a little time to put some thoughts down on paper. First let me say that an onboard mixture control now allows me to be 20 times more efficient at my pond testing. I can test props, pipes, and all sorts of things without having to re-set the mixture each time I make a change. Before, I had to reset the needle sometimes 5 times to get it perfect.

Now, I can just launch, bring the needle to a super rich setting and then dial in the correct mixture in a lap or so. Specifically, here is how I use the Mixture control:

Some boats require a fairly lean setting to launch that big prop. OK, then I set the mixture control slightly lean, which will allow me to get the boat up quickly with that big prop. Many more times it is easier to get that big prop up with a setting that is a little more on the rich side of the needle. Just as soon as the boat is up on pipe, I immediately return the mixture control to a super rich setting ( the engine will not even be in a clean two cycle). I then gradually move the mixture control knob leaner and leaner until the engine just starts to clean out. At that setting, you will make MAXIMUM POWER. It does not seem possible that the engine should be on the rich side of the needle to make maximum power, but ALL our testing has shown that to be true. At the start of the race, you may want to go a couple clicks leaner so that you will get instant response when you cross the starting line. BUT, just as soon as you get around the first turn, richen the mixture the two clicks that you leaned in, and leave it that way for the rest of the race. If you find that you are either in control of the race or behind by an insurmountable margin, you may want to richen even a couple more clicks. This is the safest way to finish the race.

If you will use this method to set your mixture control, you will ALWAYS have a perfect needle (WHAT AN ADVANTAGE). How many times have I seen people use the mixture control EXACTLY like an onboard FIXED needle. They never change it unless the boat is much to lean or much to rich. What a waste of a valuable piece of equipment!

Another misuse of the mixture control is by those with a wheel radio and a knob at the top of the transmitter. The ONLY way to change the mixture control is to take your hand off of the steering wheel while your boat is running all over the place. I might suggest that you either change the mixture control channel to the thumb wheel by re-programing your radio OR by changing the wires from the mixture control pot to the thumb wheel pot. A simple change of the three wires from one pot to the other is all that is required.

As for suggestions about the best mixture control, I will say that I have only used the OS Mixture control on my own boats, but have seen MANY use the Bob Violett mixture control successfully and I have heard that the mixture control that Competition Marine sells is also very good.

I hope that this simple explanation of the efficient use of a mixture control will be helpful.....

Be sure that you use discipline while applying this method and you will ALWAYS have the perfect needle on all your boats!


Until next time.........

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