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Norscot Dripless Shaft Seal end of boating season checklist

Now that the boating season is coming to an end, there are a few things you can do to assure your Norscot shaft seal is operating properly.  

This is a good time to locate of remind yourself where your installation tool is.  You will need this tool for seal replacement. 

1. Check the fluid level in the reservoir:
Marking your ATF fluid level with a piece of masking tape is the easiest way to monitor the level. Come the Spring season, see if the level has moved. It should stay the same all Winter.

Check below the bronze housing or anywhere in the blige for red ATF fluid. If you’re seeing ATF in the bilge you might have:

  • A damaged seal that would need replacing at your next haul out. 
  • A cracked or damaged reservoir bottle.
  • A loose tubing connection either at the bottom of the reservoir or at the top of the bronze housing.

To help determine where a possible leak might be; wipe a rag around the reservoir from the top to the bottom and down the tubing to see if any ATF is picked up. If there is, determine if the reservoir or the tubing or both need replacing.  

You can order parts here.

Other important Norscot knowledge:

  • If you discover excessive fluid loss with no ATF in the blige then one or both of the aft seals are damaged, at the end of their lifespan (roughly 1000 - 3000 running hours) and / or there is excessive shaft misalignment through the stern tube.  
  • If the fluid loss is manageable then plan to have all 3 seals replaced and your shaft re-aligned if need be at your next scheduled haul out.  Replacement seals can be ordered here.
  • If fluid in the reservoir is dark or a milky color then seawater is getting into the housing and mixing with the ATF via the spinning shaft. Please note: It is not of any immediate concern, you can monitor the fluid levels and replace all 3 seals at your next scheduled haul out.
  • Any kind of fluid in the reservoir is acceptable but you should monitor the housing temperature with a heat gun. When running roughly a half hour the housing temperature should be about 40 - 60 degrees above ambient water temperature. If it is above 130 degrees then you should address the issue sooner than later. FYI the 3 seals can handle 300 degrees of heat.
2. Check your hose clamps

Finally, make sure your 4 hose clamps are clamped down sufficiently. They should not be able to be moved by hand.  Also, make sure the 2 hose clamps over the housing and 2 over your stern tube are securely over those two things and not located over the gap in between.

We're always here for your questions- don't hesitate to call us direct at 206.920.4594 or email

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