Threaded block drain plugs

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   At the end of last year, when I pulled the two drain plugs out of the block (1/4" brass) to winterize the engine, there weren't a whole lotta threads left in the block. I've already replaced the elbow from the water pump to the thermostat housing for this very same issue.
Any ideas on how to fix this? Contemplating drilling out the diameter of the hole, tapping a 3/8" NPT hole, inserting a 3/8" x 1/4" NPT brass adapter, and loctiting them into the block. This would still allow the use of the 1/4" NPT plugs for draining the block at the end of the season. 

Please let me know how you have fixed this issue. 

Thanks!!

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1985 Nautique Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: October-10-2024 Location: Bloomington, IL Status: Offline Points: 20	Post Options Post Reply Quote 1985 Nautique Report Post Thanks(0) Quote Reply Topic: Threaded block drain plugs Posted: March-09-2025 at 11:58pm
	At the end of last year, when I pulled the two drain plugs out of the block (1/4" brass) to winterize the engine, there weren't a whole lotta threads left in the block. I've already replaced the elbow from the water pump to the thermostat housing for this very same issue. Any ideas on how to fix this? Contemplating drilling out the diameter of the hole, tapping a 3/8" NPT hole, inserting a 3/8" x 1/4" NPT brass adapter, and loctiting them into the block. This would still allow the use of the 1/4" NPT plugs for draining the block at the end of the season. Please let me know how you have fixed this issue. Thanks!!
	Brian 1985 Ski Nautique "I've spent half of my money on women, liquor, and boats. The other half I wasted."

KENO Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11197	Post Options Post Reply Quote KENO Report Post Thanks(0) Quote Reply Posted: Yesterday at 8:15am
	You should read the thread in the link below link Then after that, run a 1/4 NPT tap in the holes, whether you think it'll work or not It's worked for lots of people with the same issue.

2001SAN Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: June-26-2012 Location: Ireland Status: Offline Points: 251	Post Options Post Reply Quote 2001SAN Report Post Thanks(0) Quote Reply Posted: Today at 2:46am
	I had the same issue with the drain plug on my v drive. When I first winterised the plug literally fell out there was so little thread left. Ran the tap up it as suggested and been fine ever since.
	A little knowledge is a dangerous thing... 2001 Super Air Nautique 1989 Fairline Corniche 31 www.bannrivercruises.co.uk

Threaded block drain plugs

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