Not knowing the insides of your engine, the tacho signal wire will either find it's way to the ignition module or to the alternator side of the rectifier. If it goes to the rectifier (usually an independant box with 3 or 4 leads / terminals), based on your colour codes linked above I would expect it to share a terminal with a Green/white wire.
So, your diagram has confirmed some of the colours, so I can say with a little more certainty now:
White = stop. You should have a wire from the ignition module which will split at your console & go to both the deadman & the white wire on the ignition switch.
Brown = Start. To trace this start at the starter motor, follow the thick wire that doesn't go straight to the engine block. It should go to a relay (starter solenoid) On that relay will also be a "thin" brown wire to the console & a black to the engine block - the brown wire should go to a microswitch in your throttle / gear lever box, then on to the ignition switch's brown tail.
Red = +12V While you are at the starter solenoid in the engine, the thick cable form the battery is likely going to have a thin red also bolted to the same terminal heading off to the console. This is the +12 to feed the gauges / starter etc. It should go direct to the red wire on the ignition switch, and may have a connector near the switch to "T" 12V off for auxiliary stuff.
Blue = Choke. Somewhere near your carbs will be a solenoid. Usual story - one wire straight to the engine block, the other (blue) should go straight to the choke switch. From the other side of the choke switch there should be a connection to your switched +12 (yellow) out the back of the ignition switch - see below.
Yellow = Switched +12 v. This wire doesn't go anywhere near the engine, and should come out the back of your ignition switch. This essentially powers stuff you need when the engine is on, but stops it flattening the battery when ignition is off. This will likely have a multiple set of connectors hanging off it (probably 2 or 3). One should be connected to the choke as described above.
Pink = Warning horn. This should be connected to your alarm horn. It (just to complicate matters!) is a +ve signal when the trip switch(es) make contact (e.g low oil level, overheat) and so the pink wire on the engine could come from multiple sources, unless it goes to the "ignition" box along with the stop wire where the ignition module will deal with the spaghetti). If it doesnlt go straight to the ign module, places to check are - Oil tank level float, thermal switches usually live near the spark plugs on the cyl head. Pink wire to one side of the horn, other end to black (again, more of that below) If you don't have a Yammy horn, any electronics shop can sell you a 12V piezo buzzer. (make sure it's a loud one, as it will be buried in & muffled by your console!) In theory nothing to stop you using a 12V bulb on the panel either.
Black = Earth. This will again be connected at the engine, probably where the battery -ve wire is bolted to the engine block. This should have a multiple connector on the loom at the console end, these should go one to the ignition switch black, one to the horn and the rest are for earthing your tacho - dials - instrument lights etc.
As for the tacho you linked - maybe. Outboard tachos tend to count alternator pulses, so whether this one will have the requisite number of pulses / min when it appears to be counting sparks only an experiment will find out. Other thing (and I may be doing the maker a gross injustice here) is that "waterproof" for a car and "full IPx7" for a boat can be two very different degrees of waterproof. (as usually seen by the price
I may have a Yam tacho going spare soon (Hopefully about to finally get a complete set of matching guages! :banana
, but get your other electrics going first...