We are having a problem with the MARTEC prop that came with our new H356. We sail on Lake Ontario. For the second time, upon haulout we found that there was white buildup all over the prop. We did not have any problems with the prop on our old C-30 docked in the same slip. Last year the buildup came off with vinegar and light scrubbing. This year it took muriatic acid and heavier scrubbing to get it off. The prop now has brown/yellow spots were the white stuff was. The entire hull, rudder, through-hull fittings, prop shaft and anode show no signs of zebra mussels pr anything perculiar. The water at our slip was murky, not much evidence of zebra mussels the last two years. My intution says some this is some sort of electrolytic situation. I had the white material analyzed and the testing lab determined that it is some sort of alumnium salt. They had no suggestions as to how it got there. Ours apparently is the only prop at our club to have such a problem, except for an H-3867 that docked next to us last year. The commissioning manager at our Dealer said he's seen similar discoloration on a few other Hunter props . Hunter disavows any knowledge of a prop problem. If you rub your hand over the prop now, you can feel a bit of roughness on most of the yellow/brown spots. I sent the above info to Martec and got the following response: "Martec has just returned from a National Propeller Association Convention. One of the many topics discussed (especially by the Great Lakes Dealers) was the influx of zebra mussels, their effect on marine ecology (eating plants & algae = fewer mosquitoes & fish; water is too clean) , and subsequently, higher concentrations of calcium deposits on boat propellers (bronze & stainless). Please send your prop to Martec for examination. Cleaning or polishing the unit involves not only the removal of this growth (calcium), but leaving behind a clean & highly polished surface. The manner in which this is done is important. If the growth is removed rapidly using harsh abrasives, the surface may look shiny, but be deeply scratched. These scratches will themselves impart a roughness that is beyond tolerance. Additionally, the scratches will provide an ideal key for further calcification, micro- & macro-fouling, speeding up the fouling process and often making things worse than before. The correct procedure for polishing a blade leaves a very smooth surface, which will resist future fouling. Although slightly more time consuming to achieve, this level of finish is desirable as its long term effects on fouling & engine wear more than compensate for the initial costs. Upon inspection (No Charge), Martec will quote you on the cleaning & polishing costs (estimate @ $50)." I'm confused about what to do next. Polishing alone won't prevent the problem next year, will it? Has anybody had this freshwater prop problem? If so, what have you done about it? Related photo (Opens new browser window)