Throttle and Governor Adjustment:

From the Mud Doc: Print this...

This is for stock engines with a governor spring.

The most common PM questions I get concerns RPM, props and throttle adjustment.

The question really is, can I make my mud motor go faster.

Chances are, you probably can.

Try these simple procedures:

With engine turned off - Tape or have someone hold your throttle lever at wide open.

Loosen the throttle cable clamp located at the end of the throttle cable. Pull the cable gently until the throttle lever/slide hits its stop. Depending on the engine model, this is a high speed governor adjustment screw or a fixed bracket or tab. Tighten the cable clamp snug. Do not over tighten.

Start the engine, let idle for one minute and then run wide open. Rev the engine up slowly to allow the engine to reach max RPM without causing the governor mechanism to ossilate Check tach - the engine should run between 4000 to 4100 rpm. 4100 to 4250 for the new CDI marine engines.

If the engine runs slower, you will need to adjust the governor spring pressure.

Lets first talk about how the governor works. The governor arm and rod is connected directly to the butterfly lever on the carburetor. The throttle cable is connected to the governor arm by a governor spring. The governor arm is connected to a shaft that runs inside the engine block. As the engine rpm increases the internal governor mechanism expands by centrifugal force which in turn rotates the governor shaft and arm in a direction that decreases engine speed. As you pull on the throttle and governor spring you in fact overcome the force exerted by the internal governor and thus increase engine speed. However, as the engine speed increases and the governor arm pressure exceeds that of the spring weight, the engine slows down. As such, the controlling force you depend on is the strength of the governor spring. That is why we have different color springs with different spring strength to force the governor to yield to a set RPM. But yet no higher in order to protect the engine from over revving.

So, in order to get to our desired engine speed out of the water we want to adjust the governor spring strength to exert more pull than the governor, thus controlling top speed RPM out of the water. I will talk about how that relates to the in-water, under-load speed later.

The governor slide or rotator either has an adjustment screw or a tab that can be adjusted to slightly increase the governor spring strength. The adjustment screw moves the stop allowing the throttle to pull further on the spring, or a tab does likewise. Small block Vans have a tab, large Vans, Kohler and Kawi, a screw.

Adjust the screw or tab to pull further or harder on the governor spring. Do this a little at a time, incrementally. Check the RPM each time by slowly increasing throttle pressure to keep the engine governor from ossilating For those that have a large block Vanguard see the quick adjust procedure below.

Governor and in-water performance. With the governor properly set, you should get top performance in the water. However, you can double check your work by observing the throttle lever on the carb, making sure it is fully rotated and wide open. You can see the throttle lever pegged on its stop. (First be safe, be in open water, have full control of your motor and be familiar where the carburetor throttle linkage is located.) (This test is not subject to motor type, boat type, load, elevation, or any other conditions.) With the throttle wide open, reach around and pull or push the governor arm to see if there is any additional throttle left. Visually, you might be able to see the carburetor throttle arm pegged out on its stop or not. If there is throttle left, readjust the governor again, this time setting it at higher RPM out of the water.

Tip: While you are adjusting the throttle cable in step one, add a fingertip of grease to the cable near the cable sleeve, and tie the cable up on any part of the motor so it is higher than cable end. This will keep water out of your throttle cable and prevent freezing later on.

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For Big Block Vanguards:

- Very simple. Tape, tie or velcro the throttle lever into the full throttle position.

- Loosen the screw that holds the engine side of the throttle cable in place.

- Gently pull the throttle cable until the slide mechanism bottoms out in the slide stop. Tighten the throttle clamp screw.

- Locate the Philip's screw over a large spring below where the throttle cable connects to the throttle linkage. This is your governor fine tune screw.

- Now adjust idle. If the idle is above 1300 RPM, unscrew the gov screw until it drops to 1200 to 1300 on regular large block vanguards, or 900 to 1000 on CDI Marine engines.

- Then while still at idle, tighten the screw until the engine RPM increases. Basically, you have taken out all the slack in the adjuster where it connects to the governor spring.

- Now unscrew the screw one and one half turns.

- You can now check you max RPM and it will be above 4000 and is set to your engine's max rpm in and out of the water.

Geared properly, your engine should run between 3900 and 4100 in the water. The marine CDI engine has more power than the regular 35 stock motor and it is not uncommon to run between 4100 and 4250. This engine has a 4250 mapped coil with built in rev limiter set to 4250, however, we have noticed that when you slowly increase speed after 4000 many run over 4250, some over 4300.

Mud Doctor