knot meter through hull leak

[Jeff Tancock]

I can't find a reference, so I am reaching out to the collective knowledge base here regarding my knot meter through hull. Anyone know if Catalina installed the paddle wheel through hulls so I can access a "been there done that" guy or would it have been a dealer arranged install? My boat is an '88 (#630) and it appears that I am getting water weeping in aroung the fitting in the V-berth section of the hull. Before I attempt a repair I am looking for any comments about it...is it plastic or bronze (I can see what looks like a metal flange on the inside), is it a nut type backing that just backs out with a wrench, will I be able to just scrape away the old sealant (sikaflex?), will I need a new fitting because the old one will break, any other bits of advice before I make things worse? I need to make another scouting trip out to the boat so the more knowledge I have, the more useful it will be in planning my final assault.
Thanks for sharing any and all info and thoughts....
Jeff

[lazybone]

Are you sure it's not the O-ring passing water.

[pablosgirl]

Hi Jeff,

I highly doubt that Catalina installed your knot meter.  The electronics were installed after the boat was purchased from a Catalina dealer, either by the dealer or by some one the new owner hired after taking delivery of the boat.  We have an 88' boat as well (#551) and I know from the filled holes on the cockpit cabin top bulkhead that our boat is on least its second set of electronics.  We currently have the Raymarine ST60 Wind and Tridata displays with the corresponding thru-hull sensors and mast head unit that were installed by the previous owner.  The thru-hulls in our case are plastic.  Typically the thru-hulls and electronics are sold as a package.  If the thru-hulls are plastic, I would check with the manufacture for availability of a replacement to have on hand before attempting any repairs.   If they are metal then they will more than likely be reusable unless they are severely corroded.

Before going any further you may want to check that the nut holding the paddle assembly into the thru-hull is the source of your leak.  Then simply tighten the nut slightly may be all that is required to stop the leak.  Let me explain.  In our knot meter thru-hull there is a flange nut that holds the thru-hull to the hull and another nut that holds either the paddle assembly or a plug in the thru-hull.  This may be the case with yours, but you will have to check your boat to see.  Ours is made of plastic and I can hand tighten it to stop it from leaking from when I change the plug for the paddle assemble before we go sailing.  If the thru-hull is leaking between the hull and the flange holding the thru-hull to the hull then read the following:

The removal and resealing of the thru-hulls will require a quick haul by a boat yard.  The thru-hull can be removed by removing the backing nut and using a jig made from some 2x4 wood and a 12" long 3/8" threaded piece of all-thread, washers and nuts to pull the fitting from the hull.  Take the 2x4 stock and cut  three pieces of wood from it to make a u-shaped piece that will just straddle the thru-hull from the outside with the verticals of the "U" to be equal to the height of the thru-hull fitting.  Now drill a 3/8" hole in the center of the horizontal part of the "U".  Now cut a 4" length of 2x4 and drill a 3/8" hole through the center of the "square" side of it.  This will be the backing plate inside the boat that will force the thru-hull out of the boat.  Take the section of all-thread rod and put two nuts on one end and tighten them against one another to lock them in place.  Now take the all-thread rod and a washer and place the washer on the backing plate and push the all-thread through the washer and hole in the 2x4 backing plate.  Now take the backing plate and all-thread, and from inside the boat, insert the all-thread rod into the knot meter thru-hull after removing the paddle assembly.  Now from the outside of the boat, place the top of "U" shaped piece against the hull while inserting the all-thread through the hole in the horizontal part of the jig.  Place a washer and nut on the all-thread rod and tighten the nut until the wood jig is draw to the hull.  Now take a wrench and tighten the nut.  this may require a helper on the inside of the boat holding a wrench on one of the two nuts tightened against one another to prevent the all-thread rod from turning as you tighten the nut on the outside of the hull.  This will extract the thru-hull from the hull,  The force required will depend on the sealant used to install the thru-hull.  Hopefully not 5200.  Once out of the hull, cleanup the hull and the thru-hull and apply sealent and reinsert into the hull and tighten the backing nut. Hope this helps

Paul & Cyndi Shields

[Ron Hill]

Jeff : In the era of your boat Catalina was not installing any instruments - the dealer was.

You didn't mention the brand of the instrument or exactly where the instrument was leaking!??!
 
A Knot log meter has a fixed caulked in thur hull body and the instrument itself fits into that fixed thru hull.  Most of the instruments mounted on a curved surface have a piece of plywood on the inside of the hull to help seal.  Most of the instruments themselves have a double "O" rings to seal it to the fixed thru hull mounting. 

[Jeff Tancock]

Thanks for your thoughts on this so far. I haven't been to the boat yet, hopefully in the next couple days. In the meanwhile I have learned that the installation was local, probably dealer installed. The instuments are "Moor". I have found their website and had a look at the unit and the picture of the plastic through-hull fitting that they sell with it. Now that I have a visual, I hope to can figure out what to do when I check it in the next couple of days. I will likely need to haul out as a start.

[Jeff Tancock]

I went to the boat last night and had a good look. There was lots of sealant that I peeled off to expose the fitting and a piece of plywood as described by Ron. The wood looks wet and maybe rotted and the water is slowly weeping in what appears to be between the inner flange of the fitting and the wood, so I am assuming the seal between the plastic fitting and the outer hull is no longer good. Trying to figure out if I can do a short term fix in the water, but I think that a haul out is inevitable.