Conversion from trailer-sailer to low power motor boat

Discussion in 'Boat Design' started by Dr. Peter, Apr 27, 2010.

  1. Dr. Peter
    Joined: Mar 2010
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    Location: Zeerust, Victoria, Australia

    Dr. Peter Junior Member

    I have a Hartley 18. It was a sail boat. Now it is a low-powered (8hp) displacement camp cruiser.

    To bring about this transformation the mast, mast step and associated paraphanalia was removed.

    The centre-board casing was removed along with the steel centre-plate. The slot plugged with a board and back-filled with West System (no leaks). The resulting space inside the cabin is fabulous.

    I also removed the porcelain toilet which pumped straight out of the boat (illegal where I live) and extended the quarter-berth. You can actually rollover without having to think very much about it.

    The centre-plate was then cut up and retained as ballast along with other heavy material to equal the weight of the mast. I can't quite bring myself to attack the rudder (also steel plate) in quite the same way. The ballast sank the boat further into the water so that fore and aft trim is better under high power.

    I purchased a fixed height outboard motor mount and fitted the same in the centre of the transom. To the leg of the outboard (it was extra long) a friend and I fashioned a rudder for better low-speed control.

    The boat is used in rivers and sheltered bays - at hull speed. The 8hp Yamaha 2-stroke (dual thrust) manages things quite well in calm situations, as long as the current isn't too strong, and as long as you are going along at about half hull speed. But its not a relaxing engine to listen to when you ask it for a bit more.

    I have enjoyed the boat in this version for a couple of years now.

    The next phase of the conversion after this is to fit the motor directly to the transom and increase the hp. Hartley recommend 5-30hp for the Hartley Fisherman, a motor boat heavily influenced by the Hartley 18 design.

    1. Can the forum recommend a small modern tiller-controlled outboard?
    2. Can the forum advise me on how I might reinforce the transom?

    The cockpit now has an after-market bimini which is OK for sun protection but I doubt it will be any use in heavy rain.

    3. Can the forum point me towards ideas they have seen or constructed themselves where shelters, dodgers etc have been retro-fitted?
    4. What materials were used?

    In the photo (attached I hope) you can see the short mast. At one point a steadying jib sail was part of the mix but not any more.

    Regards one and all,

    Peter
     

    Attached Files:

  2. waikikin
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    waikikin Senior Member

    Hi Peter, definatly go for a four stroke outboard, heaps easier to live with so far as noise goes, I've had Yamaha 9.9 four stroke & it was a very good engine, I beleive they may have changed a bit, but would still be fine for your boat. All the best from Jeff.
     
  3. Dr. Peter
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    Dr. Peter Junior Member

    What about weight?

    Hi Jeff,
    I have had mixed commentary about the Yamaha 9.9 hp 4 stroke. Some very positive some ver negative. I have had some expose to small Hondas 10 and 15 hp. Four blade props. Very impressive.

    The weight issue gets me. Like a 10 hp 4 stroke is pretty heavy and for about the same weight I could get maybe 5 more hp in a two-stroke which would then push my boat along a lot easier.

    The Yamaha 8 I currently use runs at 100:1 petrol:eek:il mix and smoke is pretty much a non-issue.

    Another random thought is what about two small four-strokes on brackets. Then I could re-mount my rudder????

    Thanks for the feedback

    Peter
     
  4. Easy Rider
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    Easy Rider Senior Member

    Dr Peter,
    I really like your boat ..AND the way you are using it. I have an 8hp Yamaha that I use on a really large canoe. I only use 3-5hp and it's very quiet and smooth. But if you want to make waves w your Hartley and be as whisper quiet as possible get a 20hp Honda and run it at half throttle (or a bit less) and if thats not quiet enough throw a heavy coat over the engine. If you want to save some money find a 15hp (white) Johnson. It's actually a Suzuki. A friend of mine has a little fleet of them he rents to fishermen and has found them to be excellent. I have considered turning a larger sailboat into a trawler but that presents some significant problems.
    Your application looks excellent.

    Easy Rider
     
  5. Stumble
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    Stumble Senior Member

    Peter,

    1) I don't know about australia law, but in the US there are very different registration requirements when a boat has anything larger than a 10hp engine on it, which is why pretty much all manufacturers make a 9.9hp engine. It may be completely irrelavent for you but I would check.

    2) I have doubts that increasing the Hp would do anything but cause you to burn more fuel. I don't think the Hartley 18 was designed to be able to plane, so once you hit hull speed you can add all the power you want but won't go any faster.

    3) 4 strokes are MUCH quieter than 2 strokes, but come at the cost of extra weight and torque. Which is why most lifting outboard brackets that allow the use of 4-strokes are significantly larger than their 2 stroke counterparts ( one I looked at recently was rated for 7hp if a 4 stroke, and 25hp for a 2 stroke)

    I really like what you have done with the boat by the way! The idea of cruising under power efficiently is always a cool proposition to me.
     
  6. messabout
    Joined: Jan 2006
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    messabout Senior Member

    A while back, the devil made me buy a derelict Thistle for $75. No mast, centerboard, or rudder. I have sailed Thistles competitvely but that was not the aim. It was converted into a beach cruiser. I bought a new Johnson electric start 9.9 two stroke. I ignored the four stroke counterpart because I thought it too heavy. I knew, going in, that the 9.9 was overkill but the dealer made me an attractive offer. Turns out that the too big motor was perfect. The thing was/is whisper quiet when running at 5 knots of boat speed. In addition it sips fuel at the rate of about 12 miles per gallon. It does not vibrate or intrude on tranquility in any way. And it is not smokey. The motor has the capacity to plane a boat of this size if only it was a planing hull. The Thistle will plane under sail but in order to get it up with the engine, the boat must be heavily bow loaded. I only tried that a couple of times just to see if I could make the boat plane. Yes, but not worth the hassle, noise, rough ride, and all that jazz. The boat will run at about 6.5 knots before the wake becomes mountainous and the motor begins to do a litle work.

    One of the gratifying features of this boat is that it can outrun Donzis, Rivas, and other really fast boats. This is not a complete lie. When in a no wake zone, we just move right along with no muss or fuss, and only a tiny ripple of wake. while the super boats must merely creep in order to prevent the gosh awful wake that characterizes them.

    The Johnson or Evinrude of 97 vintage would make a very acceptable motor for the boat that you have. I suspect that there are newer models of two stroke that would be equally satisfactory and quiet.
     
  7. Dr. Peter
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    Dr. Peter Junior Member

    Yamaha 9.9hp 4 stroke

    Jeff,
    I think the 9.9hp 4 stroke Yamaha can also be fitted with a large prop. Is that right? I wonder how that changes performance?
    Peter
     
  8. Dr. Peter
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    Dr. Peter Junior Member

    Thanks for the kind words.
    The Hartley in its current form gets around all that rigging and de-rigging before and after a cruise.

    Are far as sailing goes I race a catamaran around the cans each weekend and crew for friends with large sailboats occasionally. They always need crew.

    If I hadn't made the change my Hartley would have been redundent.

    Is the Johnson a 2 or 4 stroke?

    Peter
     
  9. Dr. Peter
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    Dr. Peter Junior Member

    Motor choice

    1. I don't think the 10hp limit applies here. Any boat with a motor has to be registered.

    2. I do appreciate the hull-speed limitation. My boat is ballasted too. The extra power is about pushing more easily and quietly against the current in a river and the weather in a bay.

    When it was a sailboat it did plane on one occasion. It was a screaming reach in about 25 knots - there were three of us on board - and it was exhilerating.

    3. Thanks for the tip about the outboard bracket. I bought mine from the US over the internet. It is marked 5-15hp. I always thought this was about power. I never considered the weight issue. I have reinforced its carrying capacity but I think mounting the motor to the transom is the way to go.

    Peter
     
  10. Dr. Peter
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    Dr. Peter Junior Member

    Two strokes

    My 8 hp 2 stroke Yamaha is just a couple of years old. It was sold as a Yacht motor. Its great. It starts very earily and there are no fumes. I particularly like the dual thrust - it saves crashing into docks.

    The rudder attachment works very well at slow speed because it allows easier steering. I don't have to use power to thrust the rear of the boat around.

    Its just the noise issue which isn't terrible unless you are pushing close to hull speed. Are covers any use do you think?

    Peter

    Peter
     
  11. Dr. Peter
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    Dr. Peter Junior Member

    I have had a lot of feedback about the motor which is great.

    I have attached another image. This time we are anchored off a beach with mooring lines to the shore. Stuff that was in the cabin is now in the cockpit and a lightweight mesh to stop the insects is thrown over the bimini and clipped to the sides of the boat.

    The second part of my question for the forum was around sheltering the cockpit. Any ideas here please, forum?
    Peter
     

    Attached Files:

  12. Dr. Peter
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    Dr. Peter Junior Member

    After using the rudder-motor combination I have since refitted the original tiller and rudder and off-set the outboard back in its original position to the starboard side of the transom. The set-up is more sensitive and I can steer standing up.

    Peter
     
  13. troy2000
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    troy2000 Senior Member

    Thanks for bumping the thread; I missed it first time around. It makes me think about looking for something I can use as an overnight and weekend motor-sailor, until I get around to building the sailboat I want.

    Have you had any ideas yet about replacing the bimini?
     
  14. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    You can't over power this particular hull form. Though it does share some similarities with it's powerboat brothers, the "run" is quite different and you're best suited with a 10 HP engine or less. With 10 HP you can expect quite impressive preformance, particularly if you get her trimmed out just right.

    Remote steering, throttle and shift controls aren't terribly difficult to engineer or that costly, especially if second hand. With the remote helm, you could move forward in the cockpit and have some protection behind the cabin bulkhead. This would be the typical arrangement of a power cruiser.

    A cockpit cover could be one of several ideas. A bimini is the logical choice, like you have shown. It can be retracted and more importantly it can be modified easily. The usual modification is to make it's forward portion a "dodger", which would keep mother nature out of the companionway hatch, unless you wanted her.
     

  15. FAST FRED
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    FAST FRED Senior Member

    "The extra power is about pushing more easily and quietly against the current in a river and the weather in a bay. "

    A 5K boat goes thru the water at 5K, extra power gets you nothing, in a 5K current you might as well anchor as add power .

    Wind is different so my suggestion would be to find an outboard with a deep reduction gear that can spin the biggest diameter propeller .

    These will be created to push sailboats , not small open boats , so they should be available , perhaps used..

    You might also find sail boat pushers have somewhat larger alternators , so you can charge the house batteries when underway.

    FF
     
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