Broken Gudgeon Screws

I recently picked up a 79 Hobie 16 that has 2 broken rudder support screws. I understand this is somewhat of a common issue after doing some searching. I'm no machinist so I need an novice solution.

Is it worth it to dig out the holes to see if there is anything left to get a hold of?

Rate your cringe level on the next comment...

Should I just try and drill out old screws and run though a larger screw?

Who's been through this and can offer some advice? What did you do, and how long has it held up?

The problem with just "drilling out the screws" is that they are surrounded by a soft material (fiberglass / wood) and they are screwed into a softer material (aluminum).

Unless you are really careful, the bit will wander off-center and make a mess. You need to drill a pilot hole with a really sharp bit first.

An alternative would be to use a plug cutter to remove the fiberglass and plywood transom around the bolt so you can get a pair of pliers on it. When you finally get it out, you can fill the hole with chopped glass / resin. Use a bolt smeared with Vaseline to preserve the path to the aluminum backing plate.

After the resin goes off, back out the bolt, sand the surface smooth and reinstall your gudgeon.

If you're going to put any pressure on the backing plate (by drilling, for example), thread a bolt into one of the other holes and screw it down to hold the plate in position. I forgot to do that on my 17 and ended up knocking the plate loose inside the hull, necessitating the installation of a port.

Not to distract from the original question, but how far into the hull is the aluminum? I'd hate to start drilling a "working hole" around the broken screw only to find out its broken flush with the aluminum. I'd estimate the broken screw is about half an inch deep into the hull.

You're going to need to carve out a working hole anyway - even if it's just to see the end of the bolt.

Transom is about 3/4" thick before the aluminum plate.

Thanks a bunch man, that is some great news. Its seems a bit of a opportunity cost with this project...

If the screws were flush with the aluminum plate, I would want to attempt to drill it out, and would want the remaining holes as intact as possible to use as guides. On the other hand, I wouldn't know the screws were flush with the aluminum unless I drilled out a working hole.

Knowing the depth of the aluminum makes the decision (and solution) much easier.

I am a bit baffled though, I can't figure out why they both seemed to have broken off near the same depth. Perhaps 1/2" is where the wood begins?

I'm still interested in hearing what other folks have to say on this issue. When I get started tonight, I'd like to document (pictures, etc) this repair for future hobie owners so consensus from the get go would be great.

OK Doc,
I've been through this kind of repair on a boat without kickup rudders (pulled the plate out of the transom). It is not rocket science, the S/S screw seized in the AL plate. The screw broke, hopefully not flush with the plate. Open it up, soak them with liquid wrench (or similar) before you try to remove. If they're broke flush (or they break flush when trying to remove), like Matt said, better have a very sharp, brand new bit (for cutting S/S) a very sharp center punch, and a very steady hand. Making some kind of jig with wood to "attempt" and aline/center the drill perfectly with the screw remnant would be advisable. Patching up the fiberglass is easy.
Good Luck, let us know.

'79 huh? Are the hull decks solid?

_________________
hobiejohn at earthlink dot net
Fleet 297

Thanks John!



They appear to be, there are some holes here and there, seem to be from bad trailering, but all in all it's in pretty good condition. I ordered replacements for nearly everything but hulls and frame, so it should be a good boat for me, at least for a few seasons.

I know how to look for soft spots, but what causes them? Is it just a breakdown of the fiber + pressure?

I want to make "how to's" for this repair, as well as the patching/painting I plan to do this weekend.

Not going so well, after two days of using penetrating oil, they still aren't budging so I moved on to the "easy out" method. I've gone though countless bits thus far and am no further in on my pilot hole then when I started. Tough little bastards, can't believe they are so stuck (and hard!).

I'm about to the throwing tools stage so I'm considering other options. Any insight on hull ports? Is there enough screw on the back side to grab a hold of if I did add a port?

I can't speak for the 16, but on my 17, there was about a 1/4" sticking through the plate.

You don't necessarily have to cut a port in. I originally cut a slot just big enough to get my hand into. If you're careful and save the piece you cut out, you can patch it back in with not a lot of effort.

An alternative would be to install the one piece cast gudgeons. The holes don't line up exactly with the old gudgeons, so you drill new holes, avoiding the sheared off bolt.

Which gudeon is it - upper or lower?

Its the lower two screws on the lower Gudgeon.

I'd go with the new style gudgeons:

OK my one-piece's arrived yesterday.

I looked for a how-two on this, but it seems pretty strait forward (just like removing broken screws lol).

Perhaps someone can verify...

1. Remove all old hardware.
2. Fill old holes that don't line up with new hardware.
3. Drill new holes (1/4" is what was suggested in enclosed paperwork)
4. Tap new holes
5. Install hardware

Determie what size bolt/screw is needed.

Check to see what size hole is needed for required tap.

Drill, tap and install gudgeon.

If you drill a 1/4 inch hole for a 1/4 inch bolt/screw you won't have any material to tap.

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Thanks!

I'm hoping to start on this tonight. I'm missing out on some nice weather here so I need to get it wrapped up.

Once you have the new gudgeons on, check the fit of the lower castings and make sure they have clearance to turn. Grind away the part of the lower casting that intereferes with the gudgeons.