Northern Lights M673 / OM673 — Cooling system flushing

Maintenance

For the Northern Lights M673 / OM673, from the Northern Lights operator's manual.

Applies to: Northern Lights M673, Northern Lights OM673

Procedure

1. Marine: remove expansion tank cap and drain engine block.
2. Leave drains open; pour clean water into expansion tank.
3. Flush until drain water is free of discoloration and sediment.
4. Drain completely; close drains.
5. Refill with 50% water / 50% ethylene glycol antifreeze.
6. Check hoses and connections; repair leaks.

Full service-parts list: Northern Lights M673 →, Northern Lights OM673 →

Source: Northern Lights operator's manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.

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