G'Day Jimbo,
The short and inexpensive answer that we have used for 25 years now: use the main halyard! This has worked on all our various 15 hp 2-strokes (circa 80-90 lbs).
Obviously you need a harness of some sort on the
motor. We made ours out of 1 inch nylon webbing with a couple of those flat black plastic "buckles" to get it off and on the
motor. You position the dink amidships, just aft of the
mast. If the motor is on a bracket near the stern of your
boat, hook the
halyard onto it, have a mate put enough tension on the
halyard to just
lift the motor off the mount and walk it slowly back until it is hanging above the
dinghy. Then jump down into it and have the mate slowly lower it onto the transom. Takes maybe one minute when you have done it a couple of times.
Removal is the reverse process. This works (IMO) better than a crane on the stern of the
boat, especially if there is any sea causing the boat to
pitch -- much more motion back there!
The beauty of this system is that it costs nothing to set up... everything you need is already there, so give it a try!
Cheers,
Jim and Ann s/v Insatiable II lying Trinity Inlet, Cairns Qld Oz