SuperCat 17 Hulls Leaking

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willfuchs
Novice
Posts: 1
Joined: July 1st, 2021, 9:45 am
Boat Make/Model: 1983 Boston Whaler SuperCat 17

SuperCat 17 Hulls Leaking

Post by willfuchs »

Hi!

I just joined this forum, I bought a 1983 Boston Whaler SuperCat 17 last week! First time boat owner here, so I have lots of questions.

I checked all the rigging and sails, and sailed near shore on Lake Tahoe last weekend. After about an hour I noticed that the hulls were riding lower, so I headed in and sure enough they had quite a bit of water in them. The hulls look watertight below the waterline, the few cracks that there are look to be only in the gel coat or paint, and the two (poorly) repaired holes are well above the waterline (pictured). However, I noticed some algae or corrosion around the transom plugs, which leads me to believe that they may be the water entry point, especially since both hulls took on lots of water. Does anyone have any experience with this? Should I replace the whole assembly, or take it off, clean it up, and put it back on with some 5200 or epoxy?
Transom Plug Corrosion
Transom Plug Side View

Also, am I correct in thinking that these cracks are superficial? I've heard of some SC 17's having complete transom failures, do I need to build up the transom with more fiberglass? Also, there is a compression ding on the inside side of one of the hulls. I am away from my workshop for the next 10 weeks, does this need to be reglassed urgently? Or would it be safe to smear some epoxy over it for the time being?
Compression Ding
Two Patches
Finally, I've heard that old masts often need to be re-sealed to prevent the boat from turtling when it capsizes, but I couldn't find any info on how to do that. Do I just add some 5200 at the joints on the top of the mast? Also with the mast, I noticed that the shrouds seem loose, even in their tightest position with the extenders locked down. The mast moved side to side when I tacked. Is this how it is supposed to be? This is the tightest I can get them without undoing the shrouds themselves. Could it be because the forestay is not tight enough? The forestay seemed quite tight / was hard to get on, but I can try to get it tighter.

I'm so excited to work on this boat and bring it back to top sailing condition!

Cheers,
Will
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T Peterson
Professional
Posts: 69
Joined: October 14th, 2010, 4:00 am
Boat Make/Model: Supercat 17
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Re: SuperCat 17 Hulls Leaking

Post by T Peterson »

Hi there - and welcome!

There are lots of folks here who know more than me so if anyone disagrees with my advice - they are probably right...

For temporary fixes :

I would bed the plug housings with caulk to see if that stops the leak before using 5200. They do look suspect to me. The gunk around them is probably from water slowly leaking out while the boat was out of the water.

It's a hack but I would also smear caulk on any dings and cracks if the boat still leaks after you seal the plugs.

Don't fix two things at once or you won't know which one was leaking.

I'm suggesting caulk because it comes off and then you can properly prepare the joint/hole/crack/opening and fix it correctly.

I would get a friend and take the mast off, and then lift each end to see if you hear any water. If none, then I'd hold it underwater to see if it leaks. If it doesn't leak - don't fix it.

I have a pdf of the owner's manual and the SC17 parts list so you can see if your rigging is correct. The manuals contain information on how to set the rigging, hoist the mast, and then tighten the rigging. Neither manual seems to have lengths listed and I'm not sure why. I can send them to you.

Good luck! Tom
gahamby
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Posts: 252
Joined: July 24th, 2012, 7:02 am
Boat Make/Model: SuperCat 15#315
Location: Falls Church VA 22042

Re: SuperCat 17 Hulls Leaking

Post by gahamby »

The drain plugs are a common problem on old cats. On my 15 I removed the fittings, cleaned every thing up and re-bedded with 3M 5200. If the drain plugs look questionable, replace them! On the hull dings, I've used 3M vinyl ester putty, gel coat paste with white pigment and/or Marine Tex.
My mast leaked when I first got the boat the boat. I took the base off, tilted the mast down by the head ant filled it with water. It leaked like a sieve. I removed all the fittings, tapped all the old rivet holes for machine screws. I think Tom & Matt recommend 10-24 and/or 1/4-20. In the course of this I upgraded the main halyard to the factory Aussie ring kit. Clean up the fittings and the areas they attach to real well and bed with 3M 5200. My mast would hold positive air pressure when I had finished. On the rigging question, when I've rigged up, every thing is tight. The mast should be able to rotate easily. The only time I see slack in the shrouds is when sailing on the wind the lee shroud will go slack. You'll want check your mast rake. There's a post about it on the forum. I have found Tom and Matt most helpful with any questions I have had. Buying factory up-grade kits is as reasonable as trying to source parts yourself when the PIA factor is taken into account. Tom also sends really nice CAD drawings of the installation. Pull the end caps off the crossbars and check the half moon blocks and bolts that hold the hulls to the crossbars. Don't over tighten them! I tapped the old rivet holes for machine screws and used silicone sealer to re-attach the end caps as I wanted to be able to remove them easily. What kind of shape are the rudders/tiller crossbar in?
Take the time to read just about every post on this forum. It's worth the time.
Good luck with the 17. Post some more pics when you can.
Matt Haberman
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Posts: 601
Joined: November 10th, 2003, 8:22 pm
Location: Minnesota
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Re: SuperCat 17 Hulls Leaking

Post by Matt Haberman »

Drain plug leaks:
First off it doesn't look like the housing is sealed to the hull. I would remove the drain plug housing, remove any old caulk and clean it up so you have a nice clean surface. I would then put a nice bead of 5200 around the back of the housing and in the screw holes, insert the housing into the hull, and snug the screws down. You will have excess 5200 that oozes out around the housing that you will need to clean up with lacquer thinner.
The second thing is I would look at getting a new set of drain plugs. The threads get chewed up and the o-ring seal gets hard and they don't seal all that well after a while. Another thing to keep in mind is that most of the time you need to snug them a bit with pliers as hand tightening typically is not enough to keep them watertight.

Mast Rotation:
The mast should have 5 degrees of rake (relative to the deck in front of the beam), this is achieved by adjusting the forestay length. Once you have the mast rake correct you should adjust the sidestays to limit the mast rotation. The mast on the 17 should rotate approximately 85-90° to each side of the boat. A good visual is that the mast should rotate easily by hand (no sail up) in both directions so that the mast track points towards the end of the beam or just slightly behind it.
Matt Haberman
Aquarius Sail Inc.
http://www.aquarius-sail.com
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