Plastic doesn't hold up to "the elements" very well. Each of my new ports gets a coating of Rustoleum™ spray paint before it goes on.So the bits I bought to drill out the old corroded bolts were supposed to be cobalt bits; purchased from my local Home Depot. An online search re cobalt drill bits results mainly in confusion. Can anyone recommend a reputable brand of cobalt drill bits?
So I dropped by my local West Marine on the way home and bought a 4" inspection port, mainly because the color on that one seems closest to my white gel coat on the deck. I'm hoping that will be big enough to do the repair, but if some of you have experience with this and are convinced it's too small please let me know and I'll get a bigger one.
Somehow, I missed your idea--above.So, before I hire a professional, I had one more idea to run by the group. What if I were to take a router and cut out a rim of fiberglass around the corroded bolts that are flush with the transom, thus giving me room to gain purchase on the embedded bolts with a pair of pliers, then remove the bolts and use West System epoxy to fill in the defects after the gudgeon is bolted back properly?
I appreciate all suggestions so far.
At first I was thinking some sort of grinder, perhaps a dremel, would be easier to use than the burning idea. But then I realized that the simplest and fastest approach would be to get a small bit of plastic explosive, attach it around the screw, and blow it up. It'll quickly provide access to the backing plate.Discarding the pilot-drill part, use the smallest hole saw to make a deep cut around the unwanted machine screw. Then use a thick washer to shield the surrounding fiberglass from heat, and use a propane torch to melt/burn access to the defective machine screw. (Vise-grips are made in a needle nose configuration).
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Found while reading a Florida blog:My point re: "cobalt" drill bits was:
• there are bits made of cobalt steel
(a molybdenum series high speed tool steel alloy with an additional 5-8% cobalt)
• there are many fake cobalt bits
(bits of unknown quality steel with a cobalt surface treatment sold as "cobalt" bits)
Cobalt bits may or may not be TiN coated (titanium nitride surface treating applied by physical vapor deposition).
If not TiN coated, the cobalt bit just looks like tool steel (which is why the fakes are easy to pass off).
Uncoated cobalt steel bits will drill extremely tough, hardened materials.
If the cobalt bit has been TiN nitrided it will look like the commonly available (big box) TiN steel bits (iridescent gold in color).
TiN coated cobalt bits are superior to uncoated cobalt bits (until the bit is sharpened and/or the TiN wears off).
My '82 Sunfish has a rear inspection port...There is always the chance the plate is aluminum (which might help explain the failure of Jack's ss screws due to dissimilar metal corrosion if the backer in his boat is aluminum), but the backer in my boat is not plain steel.
Yes, I would guess the plate is probably about 3/16 of an inch. It is quite solid. There is no fold to the sides.Thanks again.
Is that s/s plate as thick as it appears? (Maybe 3/16th-inch)
Or are the sides folded in?
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Vise-Grip makes the perfect tool for that purpose. Described as a 7-inch "locking wrench", and designed for bolts, it has a terrific grip at its tips. Used for nuts and bolts, it leaves the surfaces unmarred.View attachment 23672
Images of the plate once removed. I was able to use pliers to remove the proud end of the bolts from the internal aspect of the plate.
I will take the bet on the backing plate being stainless. $100 says it is.
I'd agree that your measuring the exact diameter is a good idea. In my collection of inspection ports (for sale elsewhere here) the openings are not "as advertised" by the manufacturer!For those of you who are used to working on these boats I'm sure many of these questions seem basic but it occurs to me that there is a real possibility of creating significant damage if I don't think this repair through properly ahead of time.
Intensity has the 5" ports for $8 or $20 with a storage bag insert. I Just installed one of each on Monday. Measuring is easy, as the inner lip of the screw in cover is exactly the same size as the needed hole. You simply trace the inside ridge with a sharpie and cut the hole with a Dremel tool, using a new fiber-reinforced cutting wheel for each hole and fine tuning the cutout with a Dremel sanding drum. The port is mounted with a dozen SS #6 x 3/4 screws after drilling pilot holes. Coat the ring on the port with pure silicon before the screws go in.
My latest Sunfish is a '78 — and has a rear inspection port.The new or the old boats? There was a switch to stainless at one point, probably
when Laser Performance took over. Before that all the blocks were wood with exception
of the backing plate for the new rudder. The boat I have is mid 1970's something so I'm not
expecting much. It does have screws holding on the Gudgeon so it tapped into something, or
they just used a wood block with bolts and nuts. I'll try removing the screws tomorrow and
see what happens.