Stripped exhaust drain plug threads

[blakekrone]

So the boat I bought in CA probably never had its drain plugs removed and I had to remove them last fall to dry block the engine before having it hauled back to MN. I went to put back in the plugs today and 1 side went in without any trouble, the other side however doesn't seem like it wants to bite at all. The plugs themselves look a little rough around the edges so I picked up a new 3/4" NPT plug and that won't even bite either. It looks like the manifold was so rusted out that the threads have deteriorated to nothing for the first few turns. Is it worth it trying to rethread with a tap or do I just need to get a new manifold?

[JimN]

Originally Posted by blakekrone

So the boat I bought in CA probably never had its drain plugs removed and I had to remove them last fall to dry block the engine before having it hauled back to MN. I went to put back in the plugs today and 1 side went in without any trouble, the other side however doesn't seem like it wants to bite at all. The plugs themselves look a little rough around the edges so I picked up a new 3/4" NPT plug and that won't even bite either. It looks like the manifold was so rusted out that the threads have deteriorated to nothing for the first few turns. Is it worth it trying to rethread with a tap or do I just need to get a new manifold?

Look for a 3/4" tapered plug or fitting. If that won't grab, go one size up, maybe metric. If it won't grab a new plug, re-tapping won't work because the tap is the same size. You could also install a brass barb fitting on both manifolds (use JB Weld on the stripped one), so you can use the hose & coupler they added to the boats in about '98. It makes draining a lot easier and the fittings in the manifolds don't have to come out.

[XtwentyNot]

And a tap from a local parts store is how I fixed mine five years ago.

You might also be able to clean out the threads on the manifold with a wire cone attachment on your drill.

[JimN]

Originally Posted by Skipper

You might also be able to clean out the threads on the manifold with a wire cone attachment on your drill.

I used to see this, so I bought a 3/4" tap. If it's rusted too badly, the tap will remove rust and leaves the hole too large because removing rust removes metal, too.

[mikeg205]

Keep them holes oiled up to keep the threads in good shape... the rust creeps outside in and inside out.. a little maintenance goes a long way..

[blakekrone]

Originally Posted by mikeg205

Keep them holes oiled up to keep the threads in good shape... the rust creeps outside in and inside out.. a little maintenance goes a long way..

Exactly why I'm debating buying a new manifold. I plan to keep the boat for awhile so it might be worth it instead of having to deal with it each year.

[blakekrone]

Quick update, was a nice day for a drive and I haven't towed the boat yet any distance so I decided to run up to midwest mastercraft. They checked it out real quick with their tap and said that should work so I ran around looking for a 3/4" tap, finally found one and now I'm good to go it appears. Should know tomorrow when I start it up.

Hoping to hit the lake for an hour tomorrow night just cruising.

[waterlogged882]

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[88 PS190]

Good result, due to the taper you can usually salvage it, even if you have to thread deeper.