Anode specifications for Marinette aluminum boats (Thanks to John Althouse of Marinette, Inc for permissions)

Although anodes are commonly referred to as “zincs” the proper anode for use on the Marinette hull is actually a specially developed aluminum alloy with the designation of KA90 or SEALLOY 150. These aluminum anodes because of their material make up and the processing that they go through, give the same protection level as magnesium. KA 90 and SEALLOY 150 were the anodes that the boats were supplied with from the factory. Magnesium can be used, but only in freshwater and it will deplete at a much faster rate than the aluminum anode possibly leaving the hull unprotected if not monitored closely. Commonly available zinc is too close on the galvanic scale to provide adequate protection and should not be used. High purity zinc can be used but it is difficult to find and does not provide as much protection as the aluminum anode.

Anodes should be bolted to bare metal with Stainless Steel bolts.
Do not use wire brushes made of steel or copper alloys to strip the aluminum. (Ed. Pieces of the brush are cathodic, and don't use them in the bilge area. Wire-brushing by hand with a stainless steel wire brush is sufficient to break up the oxide. Mechanical cleaning of aluminum via power wire-brushing or grinding is not advisable because of the low melting point.)

Anode requirements:

26’, 28’, 29.5’
30” on each side of keel
12” on each trim tab
6” on each rudder

Total single engine 7’ 6”
Total twin engine 8’ 0”

36” on each side of keel
12” on each trim tab
6” on each rudder

Total 9’ 0”

37’, 39’, 41’, 44’
54” on each side of keel
12” on each trim tab
6” on each rudder

Total 12’ 0”

KA90/SEALLOY 150 anodes are available through Marinette Yachts 906-789-2248. 


(Editor's Note: Pay attention to the CAPAC meter, My boat needed more than the listed amount. Also some other owners tell me to expect that more polluted and warmer fresh water will eat up magnesium anodes more quickly.)