To reset the M11 and clear all the memory channels, you need to

1. Turn ON.
2. Press and hold FUNCTION and LIGHT.
3. Turn OFF.
4. Turn ON.
5. Release FUNCTION and LIGHT when display settles.

You can select any of the International or USA channels directly using the channel  buttons in DIAL mode. Other "private" channels can only be accessed by programming them into memory in MEMO mode. In the UK there are only two private channels available to ordinary marine users:

We are not permitted to use any of the other private channels, so most of the rest of this section is useful only outside the UK or for users specially licensed for a private channel.

1. Press and release MEMO then press and hold FUNCTION and hold down MEMO for at least three seconds. This puts you in normal memory programming mode; select the memory location you wish to program.
2. Press and hold FUNCTION, then press H/L. PRV will appear on the display. If you now press DIAL, you will find that the channel buttons offer you all channels from 0 to 116 and also a number of channels with letter codes. Select the right channel and press MEMO to confirm.

During MEMO programming, the following keys are also active:

1. FUNCTION-DIAL will cause an A to appear in the display; this makes a channel that would normally b duplex with a receive frequency shift of +4.600MHz operate in simplex at the usual transmit frequency.
2. H/L will switch the channel to low power.

I determined these by directly measuring transmit frequency into a dummy load and by using a signal generator to find the receive frequency.

* Note: I have checked this frequency carefully. Nevertheless, I have seen a "Private Marine Channels" table which shows F7 as 157.375 simplex.