You may remember that I spent several $K trying to sort out the same problem right after I bought Kristy. The blades on my Auto Prop turned freely, so I convinced myself that it was OK. I wish I'd have serviced it early in the process, and believe it would have saved me a lot of time and money.
Do you have the 78HPVolvo TMD? No smoke?
I dove on my prop the other day in StMichaels and after 6 weeks the prop had 1/2inch of algae growing on the blades.
Do yo have an AutoProp? If it hasn't been serviced in a while, that's the first thing I would do after cleaning it up.
I bought a 100psi oil-less compressor at Harbor Freight, a 50ft hose, and a used 2nd stage regulator for under $150...it works a treat as a hookah system for cleaning the bottom, unfouling the prop, changing zincs, and could even allow me to i foul an anchor in 20 ft of water. It's a 110AC pump that I run with my inverter.
Let me know if you need some help.
S/V Kristy SM243