I used to go out a lot in my 6.0m tinny and that was fine once you pick your weather. Guys fish in smaller boats than that though. Personally I reckon around 6.0m as a reasonable minimum size. For an average days trolling I would allow for say 45min at cruise to get out, 8 - 12hrs trolling depending on how hard you are, and say 45min cruise back in. Allow another 1hr at cruise to keep up your sleeve if the water is wider or a good bite develops close enough to get to at cruise speeds. Varies a bit from place to place so you would want a decent fuel reserve beyond those numbers, but they will give you a rough starting budget.

Ok, so do you reckon i would be pushing it with my 4.5m boat ive just brought 40hp? 2x25L tote tanks but plenty of room for prob another 50L, not 100% sure on the manukau never fished that side or crossed that bar before

4.5m is possibly a bit limiting for the bar unless it is perfect weather, but East coast should be OK out of places like Tuts and Whangaroa etc, but do need to really pick your weather and wait till the fish are in close. Fuel wise, take plenty. Lots of guys have caught fish in boats that size, but you do need those real flat days to get out. Waihau Bay is a good spot for a boat that size. Caught my first YFT out of a 14fter at Waihau. A beach launch at Matai Bay (if you can) may also get you close to the action and reduce your exposure time if the wind gets up.

March out of Whangaroa would be my first thought.

you dont need a big boat mate this was a report from last year in our little 4.5m boat. would happily do it again if we didnt have a bigger better boat this year