Installation and Service Manual
Precautions Against Corrosion
Anodes
The anodes fitted to the jet unit are made from aluminium alloy to MIL-A-24779 (SH) or zinc alloy to MIL-
18001H.
Do not paint over the anodes as this will prevent their correct operation. If corroding, the anodes are
providing protection and should be inspected regularly and replaced when 2/3 corroded.
It is common for anodes to be partially covered with a very loose scale, the colour of which depends on local
water conditions. Typically this scale will be creamy white, light brown or green and, providing it is loose (i.e.
easily scraped off with a fingernail) is normal.
If the anodes are not corroding when the vessel is in seawater, they are not functioning correctly and the
cause should be investigated. One possible reason could be poor electrical contact between the anode and
the component it is protecting. The electrical resistance should be less than 0.2Ohms.
Poor quality anodes may contain excess iron impurity and will tend to form a dense non-conducting oxide
film (usually charcoal grey in appearance). This condition occurs mainly in fresh water. Test for continuity
between the anode and the jet unit using a multimeter set to ohms. If the anode has to be scraped with a
knife to get a conductive reading, the anode is oxidized and must be replaced. Sanding the anode surface
provides a temporary solution, but will eventually re-oxidize.
Jet Unit Anodes
Anodes are fitted to the reverse duct, steering nozzle, reverse cylinder and the main body of the jet unit.
Anodes are also fitted internally within the tailpipe and in most jet models, within the intake.
Hull Anodes
Further anodes should be fitted on the hull, sufficient for hull protection, as determined using a portable
reference electrode and digital voltmeter and / or a corrosion monitor.
The hull anodes should remain immersed at all times.
Anodes fitted to the transom of a planing craft will not be immersed when the craft is at
speed and will not provide protection.
Anti Fouling Paint
Anti fouling Paints
Do not apply copper oxide based anti-fouling paints.
Do not paint over the anodes.
Anti-Seize Compound
Anti-Seize Compounds
Do not use anti-seize compounds which are based on graphite, nickel or copper flakes -
these will cause corrosion.
Anti-seize compounds, usually containing zinc flakes, are available for aluminium.
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Summary of Contents for HJ212
Page 1: ...HJ212 Installation and Service Manual R3A3 Jet unit Manual ...
Page 20: ...Product Description Installation and Service Manual 2 6 ...
Page 56: ...Commissioning Installation and Service Manual 6 4 ...
Page 62: ...Fault Finding Installation and Service Manual 7 6 ...
Page 82: ...Maintenance Installation and Service Manual 8 20 ...
Page 137: ...Installation and Service Manual Appendix Notes 10 21 ...
Page 141: ...Installation and Service Manual Appendix Notes 10 25 ...
Page 164: ...Appendix Installation and Service Manual 10 48 ...
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