Mercruiser Magnesium Gimbal Housing Anode | Canada Metals CM43994M Martyr magnesium anode designed to protect gimbal housing from corrosion in fresh water lakes and rivers. Mercruiser gimbal block anode early design Magnesium anode for use in fresh water applications Fits R, MR, Alpha One and Alpha One Gen II Fits Bravo I, II, III, X, XR and XZ drives Magnesium aftermarket replacement for Mercury 97-821631T3 Martyr stamping number CM43994 Current design see p/n CM821631M For Zinc anode see part number CM43994Z