Plastic thru hull. Blanking plug stuck.

Make sure it’s fully unfastened then gentle tap around circumference. If that doesn’t work a tap from outside will. Of course if you are in the water you need someone onboard 😂
 
I would be very very careful about "tapping" a plastic seacock, plastic can be very brittle and it's the biggest disadvantage of plastic seacocks and they are often advised to be used with a proprietary shield to guard against accidental knocks.
 
If as on reading I think it is probably a log housing then the blanking plug may well have a ring attached, if it has thread a length of strong cord through it and tie a hammer head to the other ( the heavier the hammer or other implement the better) then in a vertical direction swing the hammer away from the plug directly in line with the axis of the through hull. Gently at first but if it doesn't work increase the velocity of the hammer. It's akin to using a slide hammer and the vertical pull will probably release it. Next time you use it clean the plug, grease it with a silicone grease twist it in the housing and then withdraw it and regress before finally reseating it.
 
Fr J Hackett said:
If as on reading I think it is probably a log housing then the blanking plug may well have a ring attached, if it has thread a length of strong cord through it and tie a hammer head to the other ( the heavier the hammer or other implement the better) then in a vertical direction swing the hammer away from the plug directly in line with the axis of the through hull. Gently at first but if it doesn't work increase the velocity of the hammer. It's akin to using a slide hammer and the vertical pull will probably release it. Next time you use it clean the plug, grease it with a silicone grease twist it in the housing and then withdraw it and regress before finally reseating it.
Click to expand...
I'd be very wary of this approach. It wouldn't take much to sheer the outer flange off and pull the whole thing through the hull.
 
Have an approriatly sized soft wood bung handy!!! Remember, it is the size of the hole in the hull tapering down to the size of the hole in the thru hull that may be needed perhaps two different bungs.

I have read that in extremis, a root vegetable make a very effective temporary bung.
 
PabloPicasso said:
Do you suppose Daydream beleiver meant "don't ask me how I know" 🙄
Click to expand...
No. Read the thread
I was just doing Steve a favour. He asked us to ask him how he knew
So I did.
Lots of posters put at the end of a post that they want to be asked how they know something instead of just saying so.
In most cases forumites cannot be arsed to ask.
But in this case I decided I should be arsed to ask -so I asked
But if the arse cannot be arsed to answer then I will not arse about asking any more
Simple really.
 
Last edited:
PaulRainbow said:
I'd be very wary of this approach. It wouldn't take much to sheer the outer flange off and pull the whole thing through the hull.
Click to expand...

Yes ... was not so uncommon for plastic through hulls to shed the outer flange.

If there is room - I would be trying an oil filter grip on the tube and a pipe wrench on the plug ... try to get plug to turn while protecting the tube from turning etc.

My question though - Why is the blanking plug so stuck ??
 
Could be a number of reasons.

When was it last removed? Perhaps its just seized

Was it put in without any lubrication, and its stuck fast?

Was it leaking and someone used a sealant, or sealant/adhesive?

Perhaps it was jammed in with the wrong size o rings, or the o rings have swelled


Painted over with antifoul (learn Something new everyday!)

Has the fitting warped out of shape?

Has the hull flexed and trapped the thru hull fitting?

I'm sure there's other reasons I havn't thought of

Someone'll be allong soon to tell us what I've missed, no doubt.
 
Nylon absorbs water and will swell if immersed in water for long periods. I would hope that the manufacturers would have used acetal or Delrin which absorbs less water but they may have not bothered for a blanking plug.

How do I know? We made a nylon transducer housing fitted in the bottom of a VLCC ballast tank. I had a 2 hour struggle in very hot and humid conditions getting it out fot servicing. Luckily the through hull was a huge bronze valve so no danger of it breaking or sinking the ship.
 
May be possible to apply hot water to outside of the tube ? Plastic swells quite easily .. might help break the hold on the plug ?

Be careful of Freeing Fluids .... many have contrary effects on plastics ...
 
Thanks all for the suggestions.
I will have another go this week.

The fitting (50mm) is an old , before my time with the boat. I have purchased an electronic log that would fit nicely . The plastic threaded keep cap is the first problem and probably the bung will also have swelled . Looks like I will have to come out or dry out somewhere.
 
If its one of those stupid paddle wheel logs that last for about a week until a barnacle comes along I took the guts out of the thing, filled it full of silicone blanked it off. That was 15 years ago. I give it a visual every so often but basically forget its there. In fact, as we speak my boat is up the beach and it is, dry between tides as I am working on it so I may give this fitting a full inspection very soon.
 
Last edited:
andsarkit said:
Nylon absorbs water and will swell if immersed in water for long periods. I would hope that the manufacturers would have used acetal or Delrin which absorbs less water but they may have not bothered for a blanking plug.

How do I know? We made a nylon transducer housing fitted in the bottom of a VLCC ballast tank. I had a 2 hour struggle in very hot and humid conditions getting it out fot servicing. Luckily the through hull was a huge bronze valve so no danger of it breaking or sinking the ship.
Click to expand...
Apparently also happens when Trident 24 rudder tube bearings are replaced with nylon ones. Jams the rudder solid, inspiring Atlantic crossings.

To save me asking you to ask me how I know I'll tell you that I read it on the Trident OA website, except the Atlantic crossing bit, which I speculated up all by myself.

How else could that happen?
 
Snowgoose-1 said:
Thanks all for the suggestions.
I will have another go this week.

The fitting (50mm) is an old , before my time with the boat. I have purchased an electronic log that would fit nicely . The plastic threaded keep cap is the first problem and probably the bung will also have swelled . Looks like I will have to come out or dry out somewhere.
Click to expand...

Arrrrr now getting to the nitty gritty ....

Usually through hulls have a blanking screw CAP and no bung / nothing to fill the tube.

A few like my B&G have non screw blanking plugs that are a full length of the tube - that just push in and rely on O ring friction to hold / seal.

If someone has added a 'bung' .... I assume a soft wood bung ? then that TBH is a daft thing to do ....

Soft wood plugs are designed as a short term temp measure as they swell with water and seal off the 'hole' ... removal is not easy - but as long as done within a short time frame - is OK.
But if left for significant period - they can literally become permanent - risking damage to the through fitting.

The better way to fill an obselete through hull - is with a through hull item it was designed for ... ie a non-working log etc. That way - you can service the through hull as necessary etc. (I understand OP will fit a different transducer - my comment here is more for others who may consider soft wood bungs !!)

I suggest lift out and cautious attack of the problem .... even to breaking the through hull fitting and replace with new if all else fails.
 
You must log in or register to reply here.

Share this page

Top