Thanks all for your tips on our sluggish diesel Yanmar 1GM-10 in our '80 Hunter 27. Finally put on the mask and went in to take a look -- indeed the prop and shaft were severely encrusted with barnacles, despite the yard having put on a $60 paint job on the bronze last summer that was supposed to hold them off for a couple of seasons! The only good news was that the barnacles came off easier than when I had to scrape them directly off the bronze a couple of years ago. The paint came off with them, of course! The boat is doing top speed nicely now. Thanks all for your advice. Regards, Jon Zaimes "Airwaves" sailing out of Cambridge, Md., on the Choptank River