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Threaded block drain plugs |
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1985 Nautique 
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Joined: October-10-2024 Location: Bloomington, IL Status: Offline Points: 24 |
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 Topic: Threaded block drain plugsPosted: March-09-2025 at 11:58pm |
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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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Brian
1985 Ski Nautique "I've spent half of my money on women, liquor, and boats. The other half I wasted." |
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KENO
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Joined: June-06-2004 Location: United States Status: Offline Points: 11199 |
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Posted: March-10-2025 at 8:15am |
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You should read the thread in the link below
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. |
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2001SAN
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Joined: June-26-2012 Location: Ireland Status: Offline Points: 251 |
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Posted: March-11-2025 at 2:46am |
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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.
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A little knowledge is a dangerous thing...
2001 Super Air Nautique 1989 Fairline Corniche 31 www.bannrivercruises.co.uk |
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1985 Nautique
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Joined: October-10-2024 Location: Bloomington, IL Status: Offline Points: 24 |
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Posted: March-22-2025 at 8:29pm |
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Here is an update to what I just did to renew the threads in the elbow by the sea pump and water pump on the 351W engine. The threads on this got really bad about 5 years ago. Ordered a replacement off of Nautiqueparts.com. Two hose clamps and out with the old and in with the new.
I am a big proponent of keep it original as long as you can... So, I had the elbow in my stash of spare parts out in the shop. Wanted to see if I could make it work before I try to repair the threads in the block which are also severely deteriorated. Here's the procedure I used: Purchased a 9/16" drill bit, a 3/8" pipe tap, a 3/8" x 1/2" brass adapter, a 1/4" plug, and some red Loctite. I clamped the elbow between two pieces of scrap 2x4 to level up the existing and offending hole for the drill press. I clamped the 2x4 blocks to the table of the drill press once I was happy with where the drill bit was positioned over the hole in the elbow. Drilled the hole. Tapped the 3/8" pipe tap into the elbow. Cleaned off all the thread cutting oil with BrakeKleen. (My favorite shop chemical!!) I was then able to check the fit of the 3/8" x 1/2" brass adapter. Perfect. A little Loctite and a few twists of the 11/16' wrench and we had new threads in the elbow!!! Attached are some pictures of the progress along the way... Hopefully, this will help my fellow Ski Nautique enthusiasts!!!     |
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Brian
1985 Ski Nautique "I've spent half of my money on women, liquor, and boats. The other half I wasted." |
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Jonny Quest
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Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 3018 |
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Posted: March-22-2025 at 9:11pm |
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Nice. Good fix. Brass on brass will serve you well.
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2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
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