Buy a big catamaran and be done with it. Plenty of room on board, plenty of wind on the west coast. Cats don't draw too much and you can squeeze into some pretty shallow places. You get an almost limitless range with the wind ( it's free too....:) Just be prepared to spend a bomb on getting one. Have a look online.

Yeah anti foul is once a year although I’m sure you can do it yourself if you have the gear. Make sure you budget for the usual expenses plus pen and antifoul fees. Loads of people own boats over 40ft so yeah if you can afford it go for it. 

 I did it about three years ago for smae reasons more time at rotto comfortably the costs of maintenance and running costs are bloody high but i look at it as our mobile holiday home and yeah I would do it again.

If you can do your own servicing and maintenance on youe engines it is worth while as the marine diesel mechanics charge like wounded bulls !!!

 MAndurah marina insists on pretty top level insurance cover too.

Anitfoul is available at the boat lifters on the other side of the marina, ring em for a rough guide ,

susters was about 1500 per year.

Baieys marine fuel has a bowser there at inflated prices.

 ...is a good way to look at it. Although nothing like a caravan--you have to regard your pen as a home base, and travelling far and wide gets very expensive, unless you are sailing. But sailboats  have their own particular set of issues--replacement of rigging is expensive and ongoing. 

As you may know, I have a long background in seagoing larger boats, in just the size range you are looking at. It becomes a very different game when you don't have the refuge of that trailer.   Your first night in a safe anchorage will be absolutely magic. And your first night when the wind keeps rising swinging, the anchor is dragging, you are up all night and there is nowhere safe nearby to go, is the absolute pits.  

1)Yes,  the costs of maintaining a boat in the water are higher than you think. Antifouling is just the start of it, at least once a year. You'll be down in speed and burning through juice well before a year is up. You need to research pen fees.  

2) Maintenance, such as diesel engine servicing, can be DIY if you are handy with a spanner, if nothing actually breaks in a major way. You'll learn about things like stern tubes, stuffing boxes, and hull/shaft anodes as you go. But there is a lot more to fix. 

3) Need to be checked regularly--amazing how many places there are to leak. Nowadays, there must be some kind of phone app to check on bilge water levels via a sensor/transmitter. I've seen a couple of crayboats almost sink at the moorings due to really simple things.

4) You can't park these things in a shed, so external maintenance is ongoing, being out in the weather all the time. 

5) All of the extra navigation skills required are a bit of a shock, no cutting the corner in these things. Modern chartplotters are a huge help, but, if you do run aground, without damage, you ain't hopping over the side and pushing it to deeper water.

6) The family really need to be onboard with all this, its a big committment. Does anyone suffer from seasickness? I've seen this destroy peoples' dreams of boats, because a couple of family members were chronic.  Just because it's 40-50 ft, doesn't mean it stops moving. You'd be amazed at the hammering you can cop in a 40 footer when the seabreeze gets strong and you need to go into it.

7) Style of boat? Ex-crayboat style? Game boat? Floating gin palace? if you go this way, and get something with the tiny rear deck and big superstructure forward , get someone out on the rear deck on the sea trial  when you are travelling into the wind. Some of these are very prone to having an air pocket at the back , heading into the wind,  with the diesel exhaust being sucked back in, and you are living in a constant fog of diesel fumes. I know someone with a dream boat like this, and people just don't want to go with him for this reason. They don't all do it, but there are a lot that do.

Big boats are easy to buy, and can be very hard to sell. I'm not trying to put you off, if I won lotto I'd probably have an 'expeditioner' and live the dream every winter, but you need to think really hard about it. 

Good luck  

That is some solid advice there sir.  

Over the last seven years we’ve gone from a 22’ trailer boat to a 32’ sport fishing boat to a 58’ game boat.  Trailer boat was brand new, the 32 was 7 years old when we bought it, the 58 was 20 years old.

The most recent upgrade was for exactly your reasons - wanting to do longer trips with the family, and be able to stay at Rotto for a week or more at a time.  We looked at it like this - we could have bought a three bedroom holiday apartment somewhere, but now we have one we can take anywhere we want.

So what are they like to own?

Firstly, they do require more upkeep.  While a quick hose down doesn’t take too long, a proper wash and wax is the better part of a day.  You have more systems - air conditioners, fridges & freezers, toilets, waste water systems, water makers, generators, high and low voltage systems etc.  Engines and running gear are more complex - engine, raw water cooling, wet exhausts, transmissions, steering gear etc.  Setting aside the cost, there is a considerable time commitment to keeping on top of everything.  Everyone will have there own view on this, but we bought our boat to use as much as possible.  There’s only once in seven years we’ve been unable to go out due to an unplanned equipment failure.  I pretty much get things fixed as soon as I know there’s a problem.

With regard to cost, here we go.  As a rough guide an all-in cost to own, maintain and operate a bigger boat like that is about $1000/ft/year.  That’s everything - insurance, marine/yacht club fees, pen fees, maintenance, fuel, cleaning etc.  That doesn’t include nice-to-have but optional upgrades like electronics etc.  We use our boat a lot so fuel tends to dominate costs - our big boat has over 430 hours in a bit over 15 months.

On a brand new boat you could probably get away with less maintenance in the first couple of years it won’t be for long.

Look into finding a pen location sooner rather than later.  My strong recommendation is to have the boat as close as practical to your home, rather than where you think it would be convenient to depart from.  A 10 minute drive to fix a couple of small things is much better than a 25-30 minute drive, where you might find yourself putting off minor stuff that becomes major problems. The bosun’s at yacht clubs and marinas are pretty good with helping get your pen set up with ropes etc.

Handling the big boat is not that difficult but it is a two person operation.  Practice on a quiet day with just taking the boat in and out of pen.  Get used to handling, turning stopping etc.  Everything just happens a little slower and you need to think ahead a bit more.  A bow thruster is not strictly necessary but it does help.  Learn to operate the boat with the throttles at slow speeds and use the thruster only when necessary.

Now for the good stuff...

While you will be draft constrained in getting into some of the same areas as your trailer boat, you will be rewarded with a whole lot of other destination options.  At 40-50’ you will be fully self sufficient for extended stays so anywhere that has protected anchorage, moorings or pens becomes possible.  We just did a 5 day trip down to Busselton, it was fantastic.  Jurien Bay, Abrolhos and even Exmouth/Ningaloo.

Also you can do the trip to Rotto and back in a much wider range of conditions.  Obviously there are limits but you’ll no longer be worrying too much about the 15-20 knot sea breeze when getting home in the afternoon.  When you are at anchor or mooring somewhere you can comfortably ride out a day or two or stronger winds if there are nice days coming up.

Trips to Rottnest will become much more flexible.  Even for really busy periods like Xmas and new year, getting a mooring just a few months out is totally feasible, vs having to plan a year or two in advance to get accommodation on the island.  Outside of that, if you are on the shared mooring system there is always a mooring somewhere.  The more remote, and in my opinion much nicer, bays like Stark, Marjorie, Narrowneck etc become viable options for overnight stays.

Overall if you and the family/partner are prepared for the extra time and effort it will transform your boating experience.  Our young kids absolutely love the time on the boat.

 Hey Guys, some swesome reaponses, really appreciate it.

Like i said im in the early stages of looking into it, may be a case of good idea and leave it at that! Haha. I always dreamed of a large trailer boat, though as we have 5 kids, and would like to bring cousins and friends and stufff out, we have realised how limited we still are.

I will have plenty of time on my hands as I have just been put on a full time pension due to workplace injuries. Another reason why we are thinking of a big boat, as boys trips will be easier to organise haha.

I have been looking at some aussie custom builders, as I wanted a large deck, in a flybridge configuration. Alot of the newer style game boats seem to have smallish decks relative to size. 

Main usuage will be cruising around mandurah estuary, offshore fishing, rottnest days trips and extended trips, and extended trips to abrolhos and shark bay, and maybe exmouth/ningaloo after a bit of experience.

We are looking new due to reliability and maintenance costs, and the fact that we are after a pretty custom fitout. The wife also doesnt want 

Second hand, she demands new!! Looks like 2 year build times, or thereabouts.

The idea of cruising from rotto to mandurah in a seabreeze without getting cained would appeal too. Fuel usuage seems to be all over the shop, 

Ill keep looking, and dreaming.

Everything i do is double posting, dunno why?

 Not many builders in Australia do customs like that, at least not in glass.  Assegai, Norman Wright, not sure who else?

 very well put resurgence

If resale is a consideration - "production" boats dominate, i had a 36 foot boat designed by phil curran (think Precision) specifically for gamefishing, great boat we loved it, but when we were moving up in size (its called foot disease!) we waited ages for someone likeminded to buy it. (you think owning 1 boat is expensive - wait till you are stuck with 2!!)

Just my 2 cents worth :-)

I don't own a boat of that size, but I have lots of mates and a brother who do.  These are boats between 38 and 51 foot, ranging from ex cray boats to swish luxury boats.

We have often sat around having a beer and chatted about all up annual costs.  Some say 10% of purchase price, others use different measures, but the costs invariably end up at around $25-30k per year.  The largest cost is the pen, starting at $10k pa.  Add to that a Rotto mooring, antifouling, prop speed, servicing, replacing broken and worn out bits, like canopies/clears, carpets.  Honestly, something seems to be breaking every week or so, like numerous very expensive batteries, gensets, desal plants, toilet systems.

Obviously some people can justify this expense, but its significant.  When I divide the $25/$30k by the number of nights my mates use their boats, it's a high cost per night.  If you have the money....hey why not, but go into with open eyes.  

I’m just waiting for a big lotto win for one of these.

https://mansfieldmarine.com.au/mansfieldmarine/boats-for-sale/new/power-boats/caribbean-420-express/171057/

https://www.youtube.com/watch?v=vfAKBiL8sjY&feature=emb_title

 Steber?

36ft 2 Cabin Flybridge Outboard... 400k new.

 www.beneteau.com/en/antares-outboard/antares-11-fly