I know nothing about the technicalities of marine VHF, or marine electronics - but I do know this is a very nice bit of kit. It's solid, appears to be very reliable and well made and has superb battery life. Icom is the handheld radio of choice for CG and many rescue services so that's good enough for me.
Icom's tech spec on this radio says it "provides advanced waterproof protection to 1.5m depth for 30 minutes, equivalent to IPX8 rating, a first for the market place" and it certainly seems to be able to withstand being immersed.
The IC-M71 comes with a 2000mAh Lithium-Ion battery pack, that Icom say provides up to 15-16 hours operating time on the standard 5:5:90 duty cycle *. It doesn't have the facility to use normal AA type batteries as back-up **, but the battery life appears more than adequate and was still showing almost full after a weeks trip where it was on all day to get MSI and used for routine calls to CG every day. It charges in about 12 hours either from the mains or from the car if you have the optional 12v adaptor lead for the oe charging cradle. A fast (4 hours) charger is available, as are various other extras like a remote mic - see the brochure.
For comparison, my previous radio (a Garmin 725) was quite capable of virtually depleting it's battery after only a day of similar use.
With 6 watts of transmission power (most are only 5 watts ***), it also has a "mid" setting at 3 watt and a "low power" mode at 1 watt. It can be set to automatically go to standby to save power while it's not in use. All this helps battery life.
In use it's excellent, and has successfully transmitted and received in marginal areas when other makes haven't been able to. The screen is backlit and easy to read. The ergonomics are good and it fits neatly into the electronics pouch of my BA.
Icom give the dimensions as: 52.5(W)×125(H)×30(D) - but with the antenna and belt clip it's really 52.5(W)x240(H)x45(D) mms. Weight is quoted as 280g (with battery and antenna).
UK versions come with INT (which we use) and US frequencies. For some reason, the CAN (Canadian) frequencies aren't supported on the UK spec radios. Going to BC? Taking your radio?
There is one other annoying "feature" to be aware of and that is that even when the keypad is "locked", if the radio is set to dual or tri-watch function that will be cancelled if the transmit key is pressed. This can be fixed and Icom's customer service really is superb - mine had this issue when I got it last year, and when I returned the radio to them they reprogrammed it free of charge. See this discussion for more details. It is still possible to accidentally switch between power settings even when locked, again something to be aware of.
The radio itself is waterproof - the waterproof seal for the battery to radio interface is between the connector terminals at the top of the battery compartment, and the body of the radio. This makes it a good idea to remove the battery after a trip and remove any water which may have got in.
My only dislike is the lack of a visual indication of volume on the screen - the rotary on/off/vol control isn't something I like that much as it's easy to turn the vol down as the knob rotates very easily and it's hard to see where it is set. A touch of paint gives me a visual marker, which helps.
It has a lot of programmable settings and functions, so it helps to keep the manual handy - - and familiarise yourself with what buttons do what, depending on how long you've pressed them and in what combinations. That said, basic operation is very simple and logical and sound quality is good too.
A minor mod I made to it was to drill the belt clip to take a loop of cord as a lanyard attachment point in place of the wrist loop it comes with. The belt clip can be removed (it's quite bulky) and something like a loop of thin dyneema cord through the built in attachment point would do the job too. Since the article was written I've done just this and it does make the set much more compact.
Retail prices seem to range from about £210 to just over £160 at time of writing so it's really worth searching around a bit. They often come up secondhand on eBay and can be got for around £100, often either new or almost so. Which is how I got mine.
* The standard worldwide radio user application is referred to as a 5-5-90 Duty Cycle. This means users transmit (talk) 5% of the time, receive (listen) 5% of the time and are "on standby" 90% of the time (the radio's switched on - but no one is transmitting or receiving) over an 8 hour period.
A 5-5-90 Duty Cycle as related to a standard 8 hour shift:
5% Transmit = 24 minutes of transmission during an 8 hour period.
5% Receive = 24 minutes of receive during an 8 hour period.
90% Standby = 7 hours & 12 minutes of standby during an 8 hour period.
** Many sets transmit at reduced power when used with battery trays.
*** Power output is not the only factor in whether one radio will transmit better than another - I understand that antenna efficiency also plays a part.
Mike Buckley, August 2009
Note the wording in the radio - "Not intended for distress and safety purposes". How strange. I suppose that's just Icom covering their backs.
Note: These radios (as with all marine electronics) require a degree of care and it's good practice to wash them in fresh water after use. Be especially vigilant as some of the screws and metal parts are susceptible to salt-water corrosion.
See this discussion for details - it also references serious problems with the charging terminals on some different models of Icom (the IC-M31, IC-M33, IC-M35 and also the earlier Euro MIV.)
It appears that a number of people have found that the centre charging terminal corrodes away, leaving it impossible to charge the battery. The only solution seems to be to replace the battery at a cost of nearly £60 a time. Icom state the battery is a "consumable item" and refuse to replace it under warranty.
The IC-M71 as reviewed here doesn't seem to suffer the same problems as the battery has only two charging terminals.
UPDATE Oct 2015 - Icom M73
The latest version of this set is the M73 - while Icom generally have a great reputation, my partner had some problems with the M73 she got as a Christmas present in 2014.