Conversion from trailer-sailer to low power motor boat

Hi PAR/Chuck, runs best at 12 to 14 knots no slamming and a very stable boat. I am happy at 12 knots this was the target and is very economical. I wouldn't go for a deep V planing boat as I am not happy with Bang Bang big engines(expensive) and a deep V tends to roll more at rest. I used a lot of info from Lindsay Lord planing hull theory which is why the hull was extended either side of the motor to get the Beam length aspect ratio right for low speed planing. PAR is right the problem with a sailboat is the max beam is further aft than most planing hulls which makes it hard to get the ratio right.(remember I am just an amateur)

I lost one and a half years fishing time building it in my spare time, it is a lot of work my advice to anyone would be by the right hull and do it up the way you want. Tom Lathrop's Blue Jacket 24/27 has a very similar hull and he sells plans.

 

Hi PAR

If you look carefully I drew the lines of the original transom on the new transom. Came straight back from mid ships max beam and twisted the flats from about 12 degrees to 6 degrees at transom.

 

I'm not sure what's up Brendan (obviously missing something), but this doesn't seem typical of your posts. It's just a discussion forum, a rather impersonal and sterile format at that. No voice inflections to suggest real intent, just an occasional emoticon to help. There's no requirement to answer or reply to any posts, which adds to the impersonal, possibly insulting or disrespectful nature of the thing.

Doug, this is what I gathered from you previous photos. What I really wanted to see is the chine flat transition from fore to aft. This is where you went from the 3 panel to a 2 panel arrangement. I'm assuming you just "connected the dots", on the bottom to the new transom and twisted the angled chine flat in with the topsides.

 

Doug
Thanks for the info. I am looking into doing this for my next boat. My Gulfstar 37 is getting too big for me to handle. Especially weighing anchor. What was easy a decade ago is now a chore.
I am actually exploring two options. One is a 25ish trailer sailor. Kind of liking the Beachcomber 25 cat ketch. The other is converting a 25ish trailer sailor to a power boat. A "Strawler." I prefer "Strawler" to "Terminal Trawler." Just something about the word "Terminal" that has negative connotations to a senior citizen. So a Strawler it is.
Speed is not an issue with me. I have drawn a line in the sand so to speak and will use a Yamaha 9.9 high thrust outboard. The boat will travel at whatever speed that engine will provide. Be it 5 knots, 6 knots or whatever. No small diesel. Too much cost and complication. Bigger outboards would just burn more fuel for a marginal increase in boat speed.
The two boats I am leaning towards for the conversion are the Aquarius 23 or the American Mariner 23 or 26 like Kevin started with. The Aquarius 23 would be the easiest to do. Fit a good hardtop dodger with cloth sides and extend the transom probably 2 feet on each side of the outboard to provide more buoyancy aft for the heavy outboard and larger fuel tanks and call it a day. I would have a 6 knot boat. it comes with a small keel and 650 lbs of ballast molded into the hull. So no need to add ballast. Haven't decided whether I would leave in the centerboard or remove it.
The American Mariner hull shape is more like a semi-displacement powerboat with a very wide immersed transom. But it is has an extremely large keel that would require major surgery/removal which require work on the interior. And I would need to make a well for the outboard to live in.. I also don't like the interior layout as well as I like the layout on the Aquarius.
Choices, choices, compromises, compromises. Isn't that the way with boats.
Thanks again.
Chuck

 

I'm familiar with both of these hulls and they'll both squat pretty bad once near hull speed, though the American a little less so. The American has all of it's ballast in the keel stub, while the Aquarius has most of the ballast (about 600 pounds) in the hull and about 200 pounds in the board. Both boats have enough height, below the cockpit sole to build a well for an outboard, though a dog house of sorts might be necessary on the Aquarius, unless placed under the bridge deck. The American will protect the lower leg with it's keel, but will also pinch flow to the leg a bit. The American's keel will also force you to have the engine farther back than you might want, unless some of the fin is cut back. The liners on both boats are fairly easy to remove, once the deck cap is yanked.

To prevent serious squatting, you might be able to add some volume aft, maybe some foam, covered with a few layers of fabric. A wing is also an option, though it would need to be pretty big (fat) to get enough low speed lift.

 

Hi Guys, Maybe I am missing something. I modified this hull a lot of work to break max hull speed of about 5.4 knots. Chuck if you are happy with 6 to 7knots you don't need to modify the hull. My friend had an Alan Wright designed Tracker 7.7m keeler (New Zealand pictures attached) and this boat ticked along nicely hull speed about 7 knots with a 9.9hp 4 stroke mercury 3000rpm with thrust prop.

The motor was on a drop down outboard bracket which you lift and lower as to conditions. He locked the motor in position and used the rudder.

I am unfamiliar with the boats you mentioned but the mustard colored one has similar lines. Keep in mind that a drop keel and mast makes for a very stable and comfortable boat at rest.

 

I would extend the transom to make a swim step. I did this on my Gulfstar and would do something similar on probably any trailer sailor that I might convert to just power. See the before and after pictures of my Gulfstar. On the Aquarius I would mount the outboard in it's stock location on the transom with the swim step on each side of the outboard. I did this on a dinghy that I built. Photo attached. On the American I would have to make a well or might just make a cutout in the transom like the Aquarius. This is all just thinking at this stage. As I like to say my best laid plans are cast in sand at low tide.

 

Agreed, if you just want hull speed, you don't have to alter the hull's shape. I was just thinking about a 25 - 30 HP being hung, instead of a 9.9 HP.

 

I know this thread is older but I stumbled across it and really admired James May’s cruiser. I am in the process of doing something similar with a paceship 17 hull and was looking for feedback and ideas. My intention is slow cruiser with a cabin to overnight/ go out in colder weather. I intend to have sidewheel pacdles powering her as most bodies of water around me can be shallow at times.

 

A 9hp outboard on a bracket would run shallower than side-mounted paddle wheels. A Paceship isn't very big or overly heavy like a full keel boat.

 

I plan on getting a 9.9 down the road to mount on the back as additional insurance/move faster if needed. I had built a 14 foot sidewheel paddler years ago that performed nicely (the issue needed up being the hull. The propulsion system worked great) I really enjoyed the uniqueness of the paddle wheels. And I also had the idea that with all the weeds and such in the rivers they might work better when it cane to that. We took my buddy’s boat out (a Jon boat with a 9.9) and had to keep stopping periodically to get the weeds and junk off the motor

 

It seems you're looking for someone to back up your idea. I can not do that based on the parameters you outline in post #114. If you want a side-wheeler, build it. You don't need us backing you on the project. The paddle wheels and getting that set up will cost more, and run deeper in the water, than hanging a 9.9 on the stern.

 

My intention in posting was not in seeking validation for the project, it was more to share the enthusiasm with other like minded folks and perhaps pick up a few useful thoughts. I fully intend to build what I have described. I have salvaged all the parts for the proposed propulsion system so the cost is not really an issue. Comparing an outboard to paddlewheels in my experience the outboard hangs much farther down into the water than the wheels. The paddles would be at the hull line or 2 or 3 inches below. I was more interested in thoughts on the P17 hull, how she would react to the modifications. I have read a lot about de masted sailboats having more roll\being less stable. I know that the p17 does not have much in the way of ballast curious to know what the collective would know about the hull. I’ve been to the pace ship website but there seems to be little there on the p17

 

On a deviation of the theme I have a 28 foot (22' on the bottom) fiberglass seine dory that I put 5hp Honda air-cooled inboard in. I found an adapter made in Turkey to attach a ZF keyhole pattern marine gearbox onto small industrial engines. Mounted a 2.5 to 1 Technodrive gearbox to the Honda, installed a shaft in the boat and off we went. Easily does hull speed at about 2/3 throttle and when the motor wears out it's less than $500.00 for an entire new one. I doubt with proper maintenance the gear will give any problems as it's operating at only a fraction of it's rated horsepower. This may not appeal to everyone but it's a low-buck alternative to an outboard.

 

Fish53, that sounds along my same line of thinking. I have a 6.5hp aircooled engine I am planning on using on my boat. Like you said it’s a simple engine, cheap and very fuel efficient which are qualities I am looking for. Anything that may go wrong out on the water (which we know will happen) with a few simple tools my thought is that fixing the problem would be much simplified