How broke is it? You can probably baby it through the season. If you mostly go on casual day sails or don't mind having to sail home, it's not a huge problem for you right now. If your attitude is that it's a sailboat and you don't care much if the motor works or not, then you're all set. If you sail near busy channels with commercial traffic I would consider it a safety problem.
On the other hand your motor does have a issue, which will probably get worse. I would try to carefully write down the symptoms so you have specific information to give the mechanic. Such as, at what RPM & boat speed does it start blowing smoke? Record the engine temp. as well. Record any headwind, tailwind, sea conditions. Record the temp. in the engine room too. Were you running the engine room blower? The better information you have for the mechanic the more quickly he can find the problem which should $ave you.
Do you know what your max. hull speed is? Maybe you have too much pitch in your prop. and a cooling system the needs to be serviced.