using a trailer sailer for a power cruiser

I have the idea of buying a trailer sailer and removing the mast ,sails and rigging and putting a couple of 15 hp 4 strokes on it. I intend to go to the reef as I live in north qld and fuel is becoming too expensive to run my power boat. also looking at the accommodation side for 2 and 3 day trips. I am thinking along the lines of a 26 footer or there abouts. Can anyone tell me if this will work and if so the type of cruise speed and fuel consumption I could expect. Also how most trailer sailers handle under power

I believe you are right but having never had anything to do with displacement hulls I am after general info. The two motors would be a safety consideration as a 15 is not a very big motor to be running consistently. hate to break down and need a tow

The hull speed is limited to 1.34 times the square root of the water line length.
So this 26' trailer sailer is go to have a waterline length of 22'. Sq rt is 4.69. 4.69 x 1.34 is 6.28 knots...flat out unless planing on a wave.
The biggest trailable yacht in Oz was probably the South Coast Magnum 28.
And just one 15hp 4st will push a Magnum to 6.5 knots. And the Magnum is a big and heavy boat.
If you bought the popular Sonata 26 the 15hp would be truckloads of power.
You should buy only one motor.
And yer gonna need a bigger car because a 26 footer on its trailer isn't chicken feed.
Keep in mind that trailable yachts have a fair bit of "rocker" in the hull which causes pitching. What that means is that, unlike a power boat, the transom (and prop) are sometimes going to be sucking air.
If you google 'hull rocker', go to images, you'll see what rocker is.
There could be some South Coast 25's which are trailable having a lifting keel and a few were fitted with BMW (made by Hatz) 12HP diesels.
Maybe other trailable yots with diesels. GOT to be better than an outboard...I'm thinking.
On edit. If you do this then use the Hi - Thrust outboards such as those fantastic Yamahas they drive Seawind Catamarans with. A normal 15hp outboard as designed for a tinnie would be a mistake. Doable but not right. A planing outboard on a displacement hull would not be great when you can get h/thrust motors from Suzuki and Yammie.
Maybe just 6 1/2 knots will be a deal breaker?
Have fun.

Thanks brianlara and twodog. I was thinking along the lines of a sonata 8 or a sonata 26. wondering if they will handle 3 to 4 foot waves ok if it blows up as I go out 40 or 50 mile. Is there more roll in a trailer sailer when at anchor than in an outboard. Nice to know a 15 is enough power. weight not a problem as I have a 3.5 ton tow capacity. like the cruiser twodog but looking for a trailerable one. What are the older macgregor 25 like

My view is ...... Don't do it !

Best st option for you sounds like a small motor cruiser , diesel powered .

But if it were me in your shoes , I would go for a moter sailer , just like the idea of sail power .

Keel & T/S yachts are typically displacement type of hulls. Maximal speed can be acchive with relatively
small engine. My 23 f. T/ S with 9.9 Yamaha 4 stroke is overpowered. Close to 6 knots, build up a bow wave
whitch stops the boat going faster. It was previously mentioned ,displacement hull speed limitation.
There are of course a few flat bottom T/S with enough engine power , can achieve planing speed.
I would question fuel economy and distortions of the hull pushing it wrong speed.

As the long time owner of a Sonata 26, and with a lot of big boat (yacht) racing and small power boat experience - my advice is - don't do it!
As previous posts have suggested there are a lot of reasons - I will add a few more.
Most trailer sailors are lightly built relative to a similar length keel yacht (for obvious reasons) and are just not strong enough for open ocean conditions, certainly not if you get caught in a big blow. Similarly they are a compromise (as are all yachts), particularly for trailerability and have generally flat bottoms relative to most keel yachts. In any sort of medium wave conditions the hull will slam as it comes down from the back of a wave - with a bone jarring shudder - until something gives way.
The boat rolling without the mast up is not as bad as a power boat without a keel, but it is an unusual motion without the damping effect of the rig. Also the keels are generally daggers or swing boards with not a large amount of mass or surface area.
Another issue to consider is that apart from a very few (Noelex 25, Austral 8), most trailerable yachts have outboards hanging off a bracket on the transom. The issue here is not so much how many horsepower you have it is keeping the prop in the water in any sort of seaway/slop.
If you want to use it to explore inshore and daysailing on coastal waterways or shallow rivers or lake areas or even letting it dry out on a low tide, the concept is sound - but as an offshore option I would strongly recommend against it.

Different. On boatsales.com.au is a South Coast 25. I had one once, they sail pretty poorly because they were built way too heavily. I had one with a 12hp BMW diesel. They roll a bit because the hull form is very round which means that there is a lot of hull underwater. Being a pure displacement hull, unlike MacGregors which plane easily with their flat bottom, they ride very softly and have a deep forefoot. This one has a 2 hour old 8hp 4 stroke, plenty for hull speed. The beauty of this thing is that the motor is mounted in the cockpit which puts the prop about a foof forward of the transom rather than a foot behind it. The exhaust is thru prop so fumes would not be an issue other than with te engine in neutral with the boat not making any way.
This boat is a Mk1 which simply means that the coach house top is diff to the Mk2. Windows are diff.
Forgot to notice if a trailer came with it. They have an hydraulic lifting keel, the housing for which forms the table base.
Don't ask me for exact specs but it's probably 750kg heavier than a Sonata.
Went from Sydney to Lake McQuarie in mine probably ten times. Soft riding sea boat but half as fast as the Sonata, given equal wind.
If it were me buying this boat or something like the Austral 8 I wouldn't dream of removing the rig. If you find you dont like sailing then put the rig in a garage or somewhere but p le a s e try it with sails first.
This thing READS....READS...... like the ducks guts, given your proposal outline.

I lifted a 25 Robets off the bottom had sat there for 1/2 the year, before it sank it was in good condition now sails are had it and the hull is full of dead catfish...
i could see the logic in cleaning and striping it back, ripping the engine out of it mounting an outboard and a stay sail and using it to see the reef.
but not taking a operating sailboat and mutilating it.

thank you everyone for your input. My thoughts on a trailer sailer were for reduced cost to run and therefore happy to accept a5 or6 knot cruise speed as I can troll on the way out. I would have thought removing the mast and rigging from a boat designed for that purpose would hardly be deforming it in any way and by keeping them it is still a trailer sailer at a latter date with them replaced. I don't know if anyone has tried to drive an outboard boat any distance at sea at low speeds but mine is a pig to steer out there. I am also looking for something with camping facilities as a 17 ft tinny is not too good for over nighters. Where I am is protected by the great barrier reef and our forcasts do not even include a swell inside the reef so a blow is like 20 knots and waves to a max of 4 feet. Brianlara3. How thick is the hull on the South Coast and how often do the prop shaft seals need replacing. Would it handle that type of sea if needed? Would the banging down be any worse than in a power boat.

I would suggest something like Chariots Aquarious 23 trailer sailer. Single outboard up to 8 hp. Bit of a keel to give directional stability but still get close inshore. Keep the mast and sails though. The mast you will need to support the full shade cover you will need to live in those weather conditions. Down below will be unpleasant. Make a Korts nozzle for the outboard to ensure good thrust and stop any cavitation if the sea is sloppy. Drop a bit of keel down when required to aid steering if required. Any boat under 30 feet you will be basically camping in the cockpit anyway.

Check Youtube for videos of people doing the same.

Different,
I think you have the right idea looking at full displacement hulls for safe, economical cruising. I wouldn't however suggest a sailboat stripped of mast & rigging. Every boat is designed for a particular use.

There are trailerable full displacement power boats as well. They aren't common in Australia, but there there are a few around. Here's one example. http://yachthub.com/list/boats-for-sale/used/trailer-boats/roberts-21-longboat/194163
Here's a new one. yachthub.com/list/boats-for-sale/used/power-boats/delphia-nano/152301


Also consider a motorsailer. Often they have a basic set of sails that can be used on their own to power the boat in the right winds, or used to steady the rolling in a beam sea, or used as a get home emergency power if the engine fails. They are hard (impossible?) to find in a trailerable size though.

I had a Pilot 18 back in the 80's that I put together, Great little boat. Pilot Marine in Spearwood layed up the hulls and decks. You had a choice to have an open deck or a cuddy cabin.

https://www.boatlocator.com.au/item/australia/15-western-australia/89-boats-for-sale-94-sold/13009-pilot-18

These are fairly inexpensive go well with a 15 HP outboard. Modified Jcat.