Some of my most embarrassing endeavors have involved manoeuvering a sailboat under power. As captain of the Gabriel, a Cal 46 running day charters in Sant Maarten I had to berth the vessel stern-to (a Med mooring) each evening when I returned, and more than once did I mess up in a spectacular way catching the mooring line of another vessel. The problem was that I was trying to back the vessel slowly down wind which is an extremely difficult task. If you have ever had problems getting in or out of a finger pier slip, take heart, with any amount of wind or current the task becomes considerably more difficult. There are though some basics which will help you impress your dock neighbors.
Inboard diesel engines can rotate in either a clockwise or anti-clockwise direction and in some cases (for instance when a vee drive is fitted) the shaft may end up rotating in the opposite direction to the engine. The point is that it is important to know whether you have a left-handed or right handed propeller, for each type will cause your boat to manoeuvre differently. If you can see the prop then it is easy to ascertain it handedness. If you are not planning to haul out and don't fancy a dip in the bay then you can either go below and look which way the shaft is rotating or perform this simple test which I use whenever I am aboard a strange boat. With the vessel securely tied in the slip and with the rudder amidships I will give the vessel a burst of power in reverse (because if the lines break this won't send me into the dock assuming the boat is bows in). Because of the handedness of the propeller the boat will always kick the stern to either port or starboard. If in reverse the stern kicks to starboard then you have a left-handed prop; if to port it is right-handed.
Knowing whether your prop is left or right handed will enable you to manoeuvre your boat more easily. If you are motoring forwards and wish to make a tight turn then using the effect of the prop to aid the turn will result in a tighter turn than if you try and manoeuvre in the opposite direction. Remember what happened when you did the test in the slip.If your stern kicked to starboard when in reverse (indicating a left hand prop) the opposite will be true when moving forward. Thus with a left hand prop your boat will turn more tightly when attempting a clockwise circle because, going forwards, the prop will be assisting in pushing the stern to port.
The prop rotation will also affect which is the preferred side when coming alongside a dock (such as when taking on fuel). Though the wind and current will also be determining factors as well as the accessibility of the dock, if you have a choice then your manoeuvre will be much easier if you can use the effect of the prop to assist you. Assuming you have a right hand prop then coming port-side-to will be easiest. Approach the dock at about 45? and at a slow speed. When the bow is almost up to the dock you can turn the wheel to starboard and give the engine a burst in reverse. Rudder and prop will work together to push the bow out (to starboard) and the stern in (to port) while the engine in reverse will also bring the vessel to a stop. With a little practice you should be able to bring your boat alongside, parallel to the dock and stopped without the need for crew jumping ashore and attempting to get lines on the cleats to stop the boat! If wind, current or other factors mean that you have to come alongside on the opposite side then the manoeuvre is more tricky. Imagine you are in a vessel with a right hand prop and you want to come alongside side, starboard side to. Each time you use the engine to slow the boat the bow will be pushed towards the dock and the stern away from it. It is therefore important to approach at a shallow angle and at a very slow speed so that you have to use the engine as little as possible in reverse. It can be done but the procedure is not nearly so easy as in the previous case.
Whenever you are maneuvering in tight situations it always pays to do so as slowly as possible so that should things go wrong they do so slowly. Arriving at Ramsgate harbor on the East coast of England near the beginning of my single-handed voyage I planned to come starboard side to the dock (Melos has a left hand prop). I came in at 45? turned as the bow reached the dock and put the engine in reverse. But the boat didn't slow down and several hands came running forward to help the inept skipper dock his boat. I later found that the key holding the prop on the shaft had sheared and hence no reaction as I put the engine in to reverse. A little more caution on my part would have been prudent. More recently here in Portofino Harbor a vessel backed out of her slip at great speed only to crash in to a vessel astern on the next pier. The gear shift cable broke as the skipper tried to put her in to forward! Learn how your vessel will respond in differing situations and use only sufficient power to maintain steerage way. Then if things go wrong you will have more time to react and less momentum to stop.