Hole in hull under engine

[rwstage]

While inspecting the state of hoses and hose clamps on tne engines of our twin screw 2006 Mainship 400, I noticed a screw in the floor under the port engine in a location generally hard to see. I had not noticed that screw before but have found many throughout the boat that appear to be from screw in zip ties where the zip tie is gone leaving only the head under the screw. This screw did not have a zip tie head but that too has not been unusual on this boat. As the fifth owners of this boat I have spent a lot of time cleaning up such things as abandoned screws by removing them and filling the hole.

The fact that this screw was in the bilge floor and not in a stringer didn't strike me as odd until I backed it out and a small geyser of raw water erupted. I put the screw back in to stop the leak. Although I have never observed water under the port engine, I didn't like the idea of a "dry", slightly rusty screw in what amounts to a through hole below the water line.

I rolled about an inch long piece of butyl tape into a narrow cylinder, backed the screw out again and stuffed the butyl tape into the hole, working as much in as I could. That stopped the leak. Then I put in a new #10 size, 316 grade stainless steel screw with a generous butyl tape collar. I plan to monitor carefully and regularly.

Setting aside the question of why such a hole would be present in the first place, my questions to the Forum are: (1) Is my fix adequate and appropriate for the small, below water line hole (I'd like to avoid doing a haul out at this time if it can be safely avoided)? (2) Is there a better way to seal the hole without hauling the boat? And, (3) the next time the boat is hauled, how best to make a permanent repair?

Thanks in advance for your thoughts.

 

[High Wire]

It’s a temporary repair only. Check it daily for leakage knowing it could pop out at any time. Funny thing is it could last weeks, months or years. No way to know unless you pull it out and inspect.
My next thought is the cable that it used to hold down. Are there any more screws just like it? Did the genius that put the first there put another dozen or so as well?
Curious to know if the original screw was still pointed or cut off flush with the hull?

 

[rwstage]

The screw had a dull point. It was ~1/2 inch long which is what I put in to replace it.

 

[rwstage]

No other such screws in the bilge floor that I can find.

 

[Bmarler]

it's unfortunate when something like that happens. i saw a guy actually drill through his bottom one time installing some transducer wiring. what a bonehead move...
for a more permanent solution you could mix up a little splash zone, or marine tex and cover the screw. the downside is that it will be harder to do a proper repair later. the upside would be that if you cant find it again at haul out time, it would probably last the life of the boat.

 

[DWJensen]

No telling what it might have been from - I had a similar issue on my flats boat: Changed out the bilge pump and while I didn't get a geyser (was on a lift), I did see daylight. I let it dry some, roughed up the inside and then ended up squeezing some thickened epoxy into the hole and added a couple of layers of glass over the area before remounting the bilge pump/screen(sans screws).

 

[Comodave]

Agree that what you did is only a temporary repair. The real fix is to grind both sides of the hull on a 1 to 12 taper and lay in new glass on both sides using epoxy resin. Don’t use mat as epoxy doesn’t wet out mat well due to the binders in mat. Use cloth, I like 1708. What a bonehead move by the PO as stated above. I don’t have a problem drilling in the bottom of the boat as long as I know where I am drilling. I use 2 rare earth magnets and tape one inside the hull where I think I want the hole. Then go under the boat with the second magnet and see where I am actually drilling. No measurements needed and way more accurate than measuring.

 

[rwstage]

Thanks to everyone for your thoughtful feedback. Given the long lead times for haul outs this year, I went ahead and scheduled one for late April when a proper repair will be done. I'll continue to closely monitor the situation until then.

 

[kapnd]

Epoxy putty advertised for plumbing repairs is handy for such leaks, and does not require the screw to be put back in.
If you can get a partner in the water to mushroom out the putty that squeezes through the hull, it’ll be more secure.

 

[rwstage]

Good thought. I'm not sure sure I can convince my wife to get in the dark brown water here on the St. Johns River though.

Perhaps I'll don a mask and fins once we're back in clearer water on the coast.

 

[AndreHuizing]

I was wondering about the length of the screw. As I understand it's half an inch long and managed to come out the other side? Not sure about material of the boat and I'm certainly no expert but that seems very thin for a bottom! I know our Selene is on the heavy side but that has 4cm (roughly 1 3/4 inch) of GRP as a bottom.
Are you sure it's only half an inch as I would be worried for any other (hidden) screws after 5 owners...
Lots of luck! André

 

[rwstage]

I don't know how thick the fiberglass is at that location, I'll get a measure when we do the haul out. I used a 1/2" screw mostly because that was the most reasonable size I had on hand in 316 grade stainless steel.

I have scoured the bilges and lazarette and have found no other suspicious looking screws. Perhaps after drilling a hole through the hull the owner decided not to do that anymore?

 

[Wayne]

'Lo All, I had a similar circumstance on my old sailboat. I put a bilge pump onto a flat spot on the bilge where the keel extended down about 4-5' below the bilge. The boat had actually been out of the water for several months. When I drilled holes to put in screws to secure it to the bilge, I noticed that they both had a small drop of water rise above the holes. I then went on a search to ascertain the source. I found that a void aft of the bilge had been filled with foam that was waterlogged. I searched for an external source of the water and found a 3/8" hole near the bottom of the keel that had a water seep coming out of it, but was hidden by the tall grass so I had never noticed it. The sailboat sat in the cradle for almost 8 years while I built the inside, I retired from GE, and then moved back to Florida. During that time, the water quit draining and I filled and patched the hole. The only conclusion I could make was that the hole in the bottom of the keel was where the foam was injected and which had never been sealed or sealed properly. I used the sailboat for many years after that on the Gulf of Mexico an never had any problems. Loved that boat!

 

[mike66]

A scew hole won't sink your boat, and there isn't a lot of water pressure there. If it is truly a through and through hole, then when the water is clear enough remove the screw and have your wife hold something through the hole like a bamboo skewer. Dive under the boat and press some underwater epoxy over the hole. Once that sets up and the interior is dry use more of the epoxy on the inside. That should hold you until your next routine haul out.