Convert sailboat to power cruiser.

My boat already has a 4107 perkins 4 cylinder phil which pushs the boat to hull speed at a bit over 1/2 throttle. But after reading the advice and looking up other threads i think i will just add a pilot house and make the rear cockpit more user friendly for now and leave the masts and rig alone. I can use the boat while i decide if i want to go further with the power boat idea. Whatever i do it has to be right. I don't want to turn a good sailboat into a bad powerboat.

 

That's a very wise decision, you have already a "powerful" 48 HP engine. If I came to all the length to describe briefly the work to do, it was to show that is not an innocent process.
It has been done several times with mitigated results, some very bad some rather good. That depends heavily on the design of the boat.
The old designs are totally allergic, some recent ones with wide sterns and designed to be sailed flat (the floating condos) can make displacement motorboats at the expense of brain juice, plus a lot of costly and sweaty modifications, as they are often industrially made in polyester with a lot of integrated furniture and counter-molds, that doesn't help...
The best solution is in my opinion to sell the sail boat and to build or buy a motor boat.
The lone true successful mod I've seen was on a 60 feet deriveur lesté (no keel, adjustable daggerboards and the ballast already inside...) custom made in aluminium for chartering in the Antilles. The owner got fed up by the sails problems; qualified sailors hard to find, high costs and fragility so he got rid of the problem by the root. Sail boat chartering is in fact one of the best ways to lose money.
The costly transformation was made at Lorient Brittany under supervision of the NA and gave a beautiful motorboat able to beach.
And as Phil said, the change of engine on most sail boats is more complicated than an open heart surgery. However I remain sceptic about the beauty of a sail boat with short masts and re-cut sails...

 

One other thing i have been considering is to fit the best tillerpilot i can buy and use the remote control for steering in the pilothouse instead of fitting steering. . Ever heard of anyone doing that.

 

Another thing that has to be considered is how the boat will perform going directly up-wind under power, which is never happening under sail. Pitching motions may not be ideal. It is hard to modify something that was designed from the beginning to sail, to exclusive motoring, without some significant negative effect.

 

Most cruising yachts pretty much do that, very few steadfastly stand behind the wheel for hours on end. I'd usually read a paperback- lookout every page turn, push the auto helm buttons with my toes, plot about every half hour... or so, different matter inshore or busy areas though, the autohelm's usually not quick enough, some have a mini steering knob(although haven't seen one in a while & some a "tack" function that turns through 90 degrees also.
Jeff.

 

Thanks jeff. I want a tiller pilot anyway so i thought the remote would save fitting a steering system. Got a lot work before i get to that stage but .

 

You still want some form of mechanical steering instantly available, even if you use the autohelm 99%. I recall following a huge sportfish through Nassau harbor and I couldn't figure out what the helmsman was up to. When I looked through my Binocs, I saw him on the flybridge staring intently at his nav screen zoomed way, way in. He was still following a purple line, under a bridge, in heavy harbor traffic, steering with the + and - buttons! It looked like he was making a panicked call on a pay phone. Surreal.

 

I was going to do that.
Have had many thoughts since.
Powerboats have full ends. Probably for a reason. Sailboats do not have full ends.
It looks like sailboats are optimized (speed and power wise) for lower speeds that would be encountered in light winds. Powerboats are optimized for higher speeds even if they are very low speed boats.
The distributation of weight is way different.
Pitching chacteristics are way different.
And of course cabins are way different.

I was intending on striping the sailboat to nearly a bare hull and building a trawler arrangement of power (suitable for the SB hull) cabin and deck arrangements. The sailboat trawler boat would probably be a wet boat pitching a lot in head seas and have strange roll chacteristics .. perhaps even unsafe.

I'm kinda glad I did'nt do it but would probably produce a very long range trawler. But efficiency may be about the only advantage to the conversion.

I bought a 30' Willard instead.

 

A lot of sailboats use the engine for going upwind. Many have rather poor capabilities upwind, specially if the wind is to weak or too strong. Sometimes is more practical and safer to use the engine than to struggle for getting into the harbour, some entries are pretty tricky with a lot of rocks around. With the mast but not sails most sailboats are miserable in a strong sea upwind as the inertia of the mast is not damped by the sails.
I have convoyed dismasted sailboats and the things were better in pitching without the mast. If after mods you have the boat in its lines the pitching will be rarely a problem as you have plenty of volumes for dampening. The problem is more in rolling as traditional monohull sail boats are mainly designed to heel and are pretty "tender" at small angles, as the ballast has little effect, with a positive stability until around 90 degrees where the ballast has maximal effect, a few until 120. It's not the case with a motor boat designed to offer a maximal stability from the very beginning with a maximal positive around 30-35 degrees.
Modern sailboats, racers and cruisers, with wide beams and sterns designed to sail as flat as possible upwind are better candidates with already their stable shapes often with chines. A lot, even cruisers, are able to do planning and semi planning if kept light. It's a totally different school of design compared to the old school heavy sailboat as found in the States.
The oceanic racers mini-transat are pretty fast with an 50-60 HP outboard at the price of some slamming as they skim over the surface of the water. The most recent plane under sails as an australian 18 footer for hours and hours. The best mini transat are able to make 4000 nautical miles at 6.8 to 7.2 knots mean speed, with records of more than 250 miles a day, not bad for sail boats 6.5 meters long, that means that the boat was "planing" 24 hours a day with a lone very tough guy...
In cruising, the good modern French 45-50 feet designs cover frequently 200 miles day.
Two friends of mine (retired "around the world" pro regaters making a "relax" hedonist cruise with wives, lot of wine and good foods, on 2014) in the right conditions in the Pacific from Panama to Tahiti, they got several times around 240 miles while eating lapin sauté aux olives, with fresh baguettes, and sipping a Chassagne Montrachet. Ok they are pros of preparing, tuning and obtaining the speed of a boat, but that shows also the speed potential of a modern school well designed cruising sailboat for tropical seas. These boats run pretty well with the engine.

 

I have the tiller so its only a matter of stepping into the cockpit if the pilot plays up.. i would be on the tiller anyway in tight quarters. The boat you followed would have done the same with the steering wheel if he was staring at a plotter screen.

 

That is encouraging for projects of this type, then.