usually connecting the terminals the wrong way leads to the alternator diodes being burnt unless you have a main fuse b4 this.
can you trace the cables from isolator back to the motor ?

Edit:
you say batteries? how is you system set up?
did you connect one the wrong way ie one battery pos to neg of the other if that makes sense ?
or are both connected "the wrong way"
if the first and it didn't go "boooom" with melting terminals etc then you have prob blown an inline fuse.
if latter then either inline fuse or diodes (alternator)gone

guess considering you have no gauges working upftont? is that what you mean ?

sounds like a main fuse gone somewhere

 There should be an in line ignition fuse prior to the starter motor switching wire somewhere.

also is the motor 2 stroke or 4 stroke? 2 strokes will have less electrics as a general rule

 Thanks guys.. I have a dual battery setup. When I connected one battery the wrong way I immediately realised and swoped wire over. My boat is pretty old but even if alternator is gone I should have some form of power to the fuel gauge and oil. Trying to locate the fuse but can't see anything. Motor is a 2 stroke electric start.. 

 Check all wires between the battery and the ignition / starter switch. 

There is bound to be a fuse or even fuseable link somewhere in the line. 

A test light is your best hope on establishing where power is and isn't present

scano

What brand and year of motor is it? This will help us to help you... 

Most have a small fuse somewhere under the electrical cover (I have a merc which has a 20A blade fuse under there)

Steve

 Will be a fuse somewhere under there

 A poor contact at the terminal. .ie no pwr leaving the battery.  Just try changing to the 2nd battery via the isolator that you didn't take leads from. . Unless you took both off. Take you're  time.... battery test light will be extremely useful and save you possibly extended frustration. .. obviously show what's working and where the issue will exist.

 It's a tohatsu 60 1985

 All contacts seem to be ok. Must thanks all of u guys for ur help, unfortunately I'm not a mechanic and can't find the fault. I will have to take it to a proper mechanic. Happy fishing and hope u catch lots.. Tight lines.. 

 Steve, is there a fuse in the motor area you saying?Silly question but with the test light, does the crocodile clip need to be on a negative or just a bolt?

 Hi Steve

Although you're disappointed about not being able to get out in the boat tomoz apart from an "Easter Miracle" have you considered a fishing alternative for the boys. I know my two when younger would go anywhere for a fish with Dad... perhaps a bait gathering trip to your nearest marina or jetty for the next trip out in the boat  Just putting it out there for you to consider. . I'm sure the boys will love hanging out and wetting a line with "the old man"!

 Well guys thanks too all ur comments and help I looked a bit deeper in the fuse box in the motor and found a 20amp fuse. Thanks to all of ur help I can take the my boys out and only just finished. Seeing the disappointment on their  faces today was very sad, but when the motor cranked over their gleaming faces were priceless.  Thank u soooo much u are all amazing and so glad that I'm a part of this fishing community. Not sure where to go from prevally as I haven't fished here before but will post outcome.. Either way at least a beach fish is possible. Swell is up to 1.6m I think, so probably not a boat trip. Well see ..thanks again ..tight lines 

 Head straight out between breakers. . Take your time and suss it ... head to 30m mark and locate some structure.  Bottom bash with heavy sinkers and braid line if you have it.  Watch the mutton birds. . They re bloody full on. . Hence the heavy sinkers. Dhuies Pinkies and Queen Snapper.. Morwong.  Check if there are any AU number plates at the ramp carpark... theyre the local blokes and an absence of those will indicate conditions are sub par.. if not comfortable don't go.  If LB go next bay around. . BOOJIDUP bch. They'll be plenty of being and solid Skippy.. maybe the odd big KGW  and you should see pods of Salmon.. plenty of fun for the boys and yourself.  Watch the Ocean for a good 10 mins judging the swell and where you're considering fishing.  If on rocks keep away from the black slime.  For a safe water alternative park at the river mouth and walk up the Margaret River for Black Bream.. catch n release... they may not be too healthy atm.. still plenty of fun. 

 Perry u are a true gentleman thanks for the tips, will suss it out.. Cheers mate

 Not a bad boat ramp near I think its called white elephant cafe , don't need to travel far to have some fun a little bit of a bay so should be alright for launching

 I grew up in Busso but spent every second weekend at the Family farm on Kevill Rd catching marron by snare....and gilgies by hand swimming in the Margaret River on the hot days. My Dads family have been there since the 1940s and my Uncle and Aunty own and run Prevelly Park so many fun days down there as well. .. plenty of fishing adventures along the way. Used to stand thigh deep in The Box reef getting hammered by solid Skippy in the reef holes. .great fun. Let us know how you get on.  Good luck but don't "break a leg". Pez