Help Sealing Under Waterline Through Bolts for New Rudder Port

[SV/Journey]

We could really use some good advice! We have recently installed a new bronze rudder port on our Caliber 33. After weeks of work we put our boat back in the water only to discover the bedding underneath our port was leaking! We had them haul us out again, got a brand new Bud Algonquin bronze port, ripped out everything and replaced it then splashed again only to discover one of the bolts on the new port was now LEAKING!! We had them take us right back out of the water ( third haulout in 1 month) and we're back on the hard tearing everything apart! We used 4200 FC to seal the port and the stainless bolts (we are in St Thomas and stainless bolts are all we can get). We think the mistake we made was in applying the 4200 ie not applying enough, tightening everything down too much and squeezingout too much sealant etc. The bolt that was leaking was almost clean when we pulled it and the other bolts didn't have much sealant on them. Here's my long winded question: we've searched everywhere for diagrams or info on how to best apply sealant to under waterline thru bolts with washers. There's very little detailed information and a lot of conflicting information. We really don't want to do this again! We've read Maine Sails suggestions against creating a gasket by not tightening down all the way, waiting for the 4200 to set then tighten the nut but to us this sounds like the best way to do it. For anyone who has properly installed under the waterline bolts USING 4200 FC and had no leaks can you tell us how you did it? How much sealant did you use? Approx how much sealant do we want to see ooze out to create the gasket between the bolt/washer and hull? What is our approx working time with 4200 FC before we should completely leave it alone or risk breaking the seal (Installing this port is complicated one of us is outside the other in the lazarette trying to align everything)? Lastly do we need to do some type of prep or primer to get the 4200 to stick to both the bronze port epoxy bed the port sits on and the stainlessbolts? There is so much info out there pertaining to install/seal thru holes yet not a lot about thru bolts and we seen less about installing/sealing new rudder ports. If there's a better way to insure our bolts won't leak we'dreally love to hear it. Thank you in advance for your help!
PS I've attached some photos, one thing to mention is that we have switched from the bolts shown to full threaded bolts hoping to provide more teeth for the sealant to stick.

 

[SV/Journey]

Here is a photo of the exact port we've installed,

 

[dmax]

You want to recess the heads of the bolts in the fiberglass, then you can fill the holes, like this picture from MaineSail's article on through hulls:

 

[SV/Journey]

They were recessed from Caliber But we thought that was more "cosmetic" than for sealing. Will recessing help them seal better?

 

[dmax]

Absolutely - I would fill the holes with epoxy, should never leak. Also, your bottom will be smoother.

 

[dlochner]

Absolutely - I would fill the holes with epoxy, should never leak. Also, your bottom will be smoother.

Make sure all of the old sealant is removed first. You want the epoxy to bond to the hull not the old sealant. It might be necessary to drill the holes one or two sizes larger in order to remove all the sealant and fair the countersinks. If the holes are enlarged fill with thickened epoxy and drill new holes the proper size.

 

[SV/Journey]

Okay so drill out the holes a little bigger, fill with epoxy, redrill and bevel. Then countersink the bolts and use 4200 sealant in the holes and around the bolts?

 

[FastOlson]

That first picture shows sealant smeared all over the bolts and the fitting on the inside. Always a bad idea. The inside should be 'clean', and just lots of sealant around each bolt and the hole, when inserted from the outside.
Done right, there will be quite a bit to wipe off, but you always need to be sure the the bolt is well seated in sealant.
Also, before you move from "dry fit" to final assembly with sealant, wash off the mating surfaces and all of the bolt threads with lacquer thinner to remove *all* machining oils and other invisible contaminants -- you want those parts to bond thoroughly with the sealant layer between 'em.

Type of sealant is important, but not more than proper preparation.

 

[SV/Journey]

Thank you for your help!

 

[SV/Journey]

We used acetone to clean the areas and surfaces. Is lacquer thinner better? We also used releasing wax to create an epoxy "base" for the port. we cleaned that with acetone but maybe that wasn't enough?

 

[FastOlson]

We used acetone to clean the areas and surfaces. Is lacquer thinner better? We also used releasing wax to create an epoxy "base" for the port. we cleaned that with acetone but maybe that wasn't enough?

Acetone is just fine also, but harsher to your skin (and lungs) than the 'less toxic' lacquer thinner.

Aside: A friend that worked in the boat building industry in the boom times in the 70's said that the younger (dumber?) workers would wash their hands and arms in a bucket of acetone to clean up... !
...Oh My....

 

[SV/Journey]

 

[dLj]

Is this image the outside, or water side of this joint?

 

[SV/Journey]

Yes this is the outside where the rudder goes into the hull. Here's another photo.

 

[SV/Journey]

Is this image the outside, or water side of this joint?

View attachment 191977

Yes this is outside where the rudder post goes into the hull.

 

[Tom J]

PS I've attached some photos, one thing to mention is that we have switched from the bolts shown to full threaded bolts hoping to provide more teeth for the sealant to stick.

I think your logic is a little faulty. The threads provide a path for the water to intrude into the boat. From experience, I can say it is very difficult to seal the threaded portion of a bolt. I's suggest sticking with bolts with shoulders, and bedded as mentioned previously here.

 

[SV/Journey]

I think your logic is a little faulty. The threads provide a path for the water to intrude into the boat. From experience, I can say it is very difficult to seal the threaded portion of a bolt. I's suggest sticking with bolts with shoulders, and bedded as mentioned previously here.

Hmmm the original bolts were full thread. When we pulled the bolts down in the photo after discovering the leak hardly any sealant was on the "smooth" part of the bolt. Only the threads had sealant. However I'm realizing more and more that we really screwed up the sealant.
We will definitely take your suggestion into consideration, thanks!

 

[SV/Journey]

Hmmm the original bolts were full thread. When we pulled the bolts down in the photo after discovering the leak hardly any sealant was on the "smooth" part of the bolt. Only the threads had sealant. However I'm realizing more and more that we really screwed up the sealant.
We will definitely take your suggestion into consideration, thanks!

One other thing, these bolts are made to use with a washer. If we used them how would we countersink them with a washer? I did try to research that because we actually prefer using them because they are larger but I couldn't find how to countersink with a washer.

 

[dlochner]

One other thing, these bolts are made to use with a washer. If we used them how would we countersink them with a washer? I did try to research that because we actually prefer using them because they are larger but I couldn't find how to countersink with a washer.

You should use a flat head screw if you are going to countersink the screws.

 

[Ralph Johnstone]

Your original installation with the bolts and washers may not be the very best in theory best but it should work well. My only question is: WHY THE HELL SO STINGY WITH THE SEALANT ? I use more sealant when dealing with above water installations. You want sealant gushing out of every piece of hardwear on the OUTSIDE of the hull as per @FastOlson but not on the inside. This must be clean. Wipe it off when you're finished.

Tighten nuts FROM THE INSIDE ONLY. Do not tighten the bolt heads from the outside under any circumstances. NONE ! ! ! ! !

Last question, are the bolts snug in the holes ? Snug but not sloppy.

There is no reason whatsoever for your arrangement to leak if you:

- use plenty of sealant
- tighten from the inside ONLY
- ensure the bolts are a snug fit.

EDIT: coat the smooth shaft of the bolt with LOTS of sealant as it slides into the hole through the glass. This further ensures another seal to rely upon.