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Hello everyone. I am new, perhaps this has already addressed. I am restoring a Sweet Caroline 20. Decided to widen the transom in order to fit a more modern tiller motor. The plan is to use the boat for extended expeditions on Lake Powell, Mead, in Grand Canyon etc. These trips may involve 200-300 miles of running with no refueling stops. It would be nice to be able to get on plane with a full load while keeping fuel consumption to a minimum. At my job driving boats through the Grand Canyon we run 20 or 30 hoarse Honda, Tohatsu and more recently Evinrudes. An 8 day trip on a 35' inflatable uses about 40 gallons of gas. Needless to say we move along at about 4 miles per hour with the current adding another 4. My boat came with a Johnson 35 2 stroke which the prior owner said will easily get it on plane with full load but I suspect the fuel consumption may be a bit high. Any advice would be greatly appreciated.
Elkanah, Scottsdale, AZ.

Elk

I would think that 25 to 30 hp would be plenty. The specs give displacement of 1600# with a hull weight of 640#. That is 950# motor, fuel, gear and passengers. Fully loaded at WOT a 30 hp might put you at 24 mph. You'd probably be on a good plane at 20. If it uses 2 gal/hr (I think that's high for a thirty) a 300 mile trip will need 30 gals. That's about 210# of fuel. The engine is about 200#.

Anyway, that's the idea. Now you can play with the numbers. I think I'd go with a smaller tank and carry Gerri Cans for extra fuel on the longer trips.

Bill

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Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
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Thats quite an undertaking, modifying the well boat. Widening the well area further reduces the bottom surface for planing unless you add back some filling in the well area. You may also end up with some porpoising issues too because of the ruck and further reduction of bottom. You should probably add some form of wedges to the well sides after you see what you have when you are done and seatrial it, tweaking as needed the amount that you need to correct any of the issues of running angle and plane angle. I would think that building a new dory style hull would be easier and surely work better for hauling loads of cargo and carry fuel without further restricting the deck space either, whether it be with jerry jugs or additional fuel tanks. While the four strokes are very fuel efficent the weight is a bit more even though the new engines are coming down in weight. I had a 40 hp suzuki that weighed almost identical to the new 70 new designed Yamahas. You really don't have to use all the rpms either when running, which further minimizes the fuel burn when no loaded.

Thank you gentlemen for your responses. I had come to similar conclusions but it is a relief to have them validated by those of you with more experience. Because this boat was so over built by the original owner it will probably end up 100 pounds heavier but I would prefer that since I tend to get myself into fairy extreme conditions.
As for the transom I will be moving the walls of the transom box to the outside of the original frame members they were attached to. In other words I will not reduce the hull size but will have a modest splash well. Similar to what Steve Mitchell did with his in the photo gallery but not as wide. By cutting off the old transom at the level of the floor and pinning the new one to the old I will be moving it to the rear about 2". Since the engine did not fully clear the stern of the boat when lifted with the original design it hardly matters. Just need to be cautious when getting the engine up. Will also be adding trim tabs to help compensate for the handling issues. Working on the transom today will post a pic soon.

I am not at all worried too much about the weight issue for your particular use. This maybe some advantage for sure as long as power is the propulsion.

A productive week! Put 3/8 ply on the rear interior hull. Was fiber glassed originally but cracked vertically along the middle. I figure ply adds strength and it is one less thing to fiberglass. Cut out and have begun to resin the transom parts prior to installation. Instead of lockers on either side of the transom decided to go with a step / small deck with flotation inside. Seal it all up and forget about it. Should be large enough for a medium - small gas tank. The boat is putting on weight for sure but that just lends stability in rough water. In the Grand Canyon on big rapids days the dory boat operators always go for the heavy gear like tent bags and cast iron dutch ovens to help weigh themselves down. The 20' Sweet Caroline will no doubt row like a barge compared to the 18' dories we use at work but it should be great compared to the 18' AVON pro inflatables with a ton of gear and passengers.

Since you are doing all the reconstruction, you can move the engine transom and well transom back a wee bit further, closing up the hole a bit and also be ahead of the game in the area or floation and stability. Take your engine cowling width fore and aft and some additional inches for the turn diagonal distance and use that as a gauge in which to reduce the distance and size of the hole running length ways. What this does is also gives you additional advantages of running the engine with the motor trimmed up and turned with the wheel while underway so that the prop and leg does not hit the well sides, which happens a lot in the longer wells.
The shot depicts what happens in trimming and when the engine is running in shallow water in turns. The prop is clear of the sides when the engine is back to the absolute minimum.

Oyster
After reading your letter I spent the better part of the next day measuring and thinking. Moving the engine back does serve dual duty in that it gets the prop out of the boat and it gives the hull more surface area. It also dictates cutting a larger area from the rear outer hull of the boat to clear the engine foot.
The environment I am expecting to operate in would require me to get the engine out quickly and briefly if I misjudge some current and get near shore. However, following waves blasting up through the motor well are a major concern. These can occur at any time while driving in rough weather. As a result it seems wise to accept potential dings in the motor well rather than water blasting into the boat in volume. Hopefully I can build a wedge shaped wooden guide with a stop that allows me to pull the engine out and it will self orient vertically and not tag the well with the prop. The motor can be locked in the upright position with a rope.
Another concern is having the boat swing into a rock backwards. If the motor sticks out too far it may become the bumper. Even a hard boat will absorb a shore hit better than a motor.
Part of it was my impatience and the desire to forge ahead with the plan. Your ideas have merits to be sure.
For better or worse here is where it is at now. Transom, flotation and rear decks.

You will find that the transom angle gives you a lot of reserve bouyancy for rough water, which in turn gives these style boats a different reaction. These transom angles stems from the early days of dories, surf dories to be exact for the fishing industry. The power ones are nothing more than wider rowing versions. So the issue of water in the well or over the transom as with many small runabout type boats is less of an issue to really none with the experienced helmsman. I have a 12 footer that I have on occasions fished the inlets and run across corresponding tide and wind conditions without a single issue. I have even loaded the boat with additional passenger lowering the rails to the water and still felt safe.
This boat is a regular hull offshore to over 40 miles with no cap at the transom and has been a favorite style for decades. But the design originated from commercial fishing hulls in all types of weather.




Check out another build thats taking place called the Bartender, which has a well inside the boat and used in the pacific northwest too. So moving the well back and cutting the transom cutout more is really not as big of an issue as long as you do not change the transom angle. You can also add back some splash guards too along the well sides as yet another deflector.

This is another add on for the well area which works well too for the absolute purist.

Check out this setup. This allows storage and a place to actually stand up for fishing out of the stern area for your use.


There is a nice platform foward that has worked out grand. Some folks install their fuel in that area too, which transfers some of the weight and offsets some of the issues with the loss of bottom for these style boats.

Yes you are correct about the design. Having the motor farther back is desirable in almost all instances. My wording in the last entry was very poor. Thanks for the great pics and building ideas. The traditional rubberized canvas spray skirt around the engine would be my first choice.
In the environment I work in water is coming in the back regardless. Yes having a larger motor well with the motor forward will result in less interior room and less than ideal handling. Still I would still rather hit hull first into a wall than prop first when the motor is lifted ( the skegs have been sheered off of most of our engines by the time they have 150 hours on them ). I like the idea of protecting the motor as well as having a larger surface in the back for the boat name and associated art. After all Grand Canyon boatmen are all attention whores at heart and wooden boats down there reflect that. Mine will be no exception. With over 2000 hours of commercial operating at the helm believe me when you run a class 4-5 rapid there will be buckets of water coming up through that well regardless of the transom angle. Your 12 footer looks like it would be a lot of fun down there and I would encourage you to try it... But I sure wouldn't overload it As it stands I can think of at least over a dozen places where waves could break at the wrong time and turn the 20' Caroline into a submarine. Can't wait!
By the way nice choice on the Honda engine. I have run many different engines and the Hondas have taken more abuse and stayed running more than any other. In very low water I once had a very bad run where the engine was kicked up and out of the water so hard that the lower unit housing cracked all the way around and the transom jack ass plate broke on impact and the engine never stalled and kept running long enough for me to get to shore and change motors. Hondas kick butt, and keep running when you kick theirs.

So much for my powers of observation. You are running an Evinrude.
Perhaps I should stop writing these entries at night after long days at work.
We are currently using the new E-Tecs in Grand Canyon. I was leery of them at first but so far they have performed very well and the acceleration is unmatched. That synthetic 2 stroke oil is pretty pricy though and I worry about the computer but so far so good.
All of the guides don't like the location of the kill button as we often turn the motor off with our butt or hip when jacking it out of the water.
Really good design of tiller handle other than that. Toughest one I have used yet. That was a Honda weak point.

You did ok,there was a Honda in one of his pics!!

He has a Yamaha on the little 12'....he runs them all!!

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I am debating between a 2 and 4 stroke 30 horse. The 4 strokes weigh a lot more. Does anyone know how much weight you can put on the transom and punish the boat in rough water without tearing it up? I integrated the transom with the rear flotation chambers to help beef it up and have overbuilt every other thing that has been redone. It looks like someone put a 50 on a sweet Caroline in the photo archive but it looks like a 2 stroke. Seems like a lot of engine unless you are chasing ships in the Persian gulf.
It is awesome having all you experienced boater's knowledge on this site.

Lookin gud! Keep up the good work and please post lots of pics.