I need to replace the inspection port covers on my nacra 5.5. One of them has a big crack on it and won't seal, plus they both need new O-rings. They are the curved/contoured viking ports that were origional equipment (4"). Since these are out of production does anyone know of any compatable ports on the market so I could just drop a new lid in or am I going to have to buy new lids and ports and drill out rivets, contour a flat port etc. If I have to put new ports in does anyone know of pro's/cons to keeping the 4" vs moving to a 5" or 6" port? I'm assuming the smaller the port the better for hull strength. Also any brands you'd reccomend or avoid for the ports? I know aps has "RWO" brand ports and murrays has some no name ones but neither has the contoured ones so I guess marine tex or JB weld on the hull to make a flat surface.

many lids will work on other brands so you could try a west marine one (or other)
west marine (and others) sell orings
I know the viking ports i had would work fine with most standard screw lids
there are old school ones that have a different thread

i wouldn't open up the can of worms of replacing unless it is a last resort
it is a fair amount of work to do correctly

There is a write up on this site somewhere of how to do it correctly

I couldnt find the curved ones for a good price. Viking is typically the brand I see on almost all cats. I mean they are just the standard ones with the mounting ring cut out to a slightly curved shape. I just got the standard flat ones cheap off ebay and before screwing them down to the deck just pumped a bunch of marine sealant under the curved area for support. Once it was dry the mounting area was essentially now flat.

If you dont wait for the sealant to dry you can bend the mounting ring with the screws and the hatch will jam when you try and screw it in.

Thanks for the tips, guess I'll order some form APS or Murays and hope for the best, maybe I'll luck out and the threads will match. I know murrays is pushing these plastic bolts to secure them, the factory used what looks like aluminum rivets, any benefit one way or the other? I'd imagine there's not a lot of stress on the area since you're hand screwing it down so either one would work.

ss scews with nylocks would be my choice
rivets can be rough on fiberglass and you can't control the pressure like you can a screw
nylocks so they can't worm out

If you plan to do anything with the ports other than venting the hull (i.e., if you want to actually store something in the hull or have access for doing a repair), I would go with at least 5" diameter ports. For me, a 4" port is barely large enough to squeeze my arm into. It's pretty easy to open up the rough hole in the hull to 5" diameter and there a several methods to do this depending on what tools you have available.

I agree with the use of stainless screws over nylon screws or rivets. You can't really control the clamping pressure when using rivets which can cause sealing problems or damage to the inspection port housing. Nylon rivets can also be a PITA to tighten and the nylon can get brittle and break if you ever need to take the port apart later.

sm

OK, I think you sold me on the 5" port (plus you can get a cupholder insert). Would you guys use a caulk or something soft to even the curvature or try and use something more solid like marinetex or JBWeld?

yea , as usual... i don't agree -
to each their own...
but unless you need to gain more access (i.e. repair) ...

i would suggest to most: don't hack up your boat - don't start an un-needed project

they always turn into much more work, expense and in the end -more hassle than expected (for me, ymmv)

i would suggest you test out the new lids you ordered and MAYBE purchase a 4" fat bag (that can carry a bucket load of crap )

If you are hell bent set on cutting into your beloved catamaran ... so you can "stick your arm" in her ...

When i had ports and hatches professionally installed on my boats, "they" have built up the curve under the lip with shims:with some type of starboard product (delrin)

there is a "good" write up of one technique somewhere on this site .. anyone know the link?



Edited by MN3 on May 16, 2018 - 07:41 PM.

I can only speak from my personal experience. Anytime I've had to deal with sticking my arm in a 4" port (my first H17 had them and my H18 has them behind the rear crossbar), it is literally a pain - my arm barely fits in and gets scraped up on the edge of the port. If you don't feel comfortable cutting into your boat, then for sure, don't do it. But for me, the 4" ports are just about useless when it comes to providing functional storage or internal hull access.

For matching the deck contour, marine silicone caulk should be all that's needed. Place the access port housing into the hole and use it as a template to mask off the surrounding deck area (you don't want caulk getting into the non-skid). Then place a liberal amount of caulk on the housing flange, place the flange back into the hole and press it down until it starts to contact the deck and the caulk starts to squeeze out (you can also add more caulk if there are any voids). Install the screws (with caulk) and tighten them lightly. Then use a flat mixing stick or squeege to clean off the excess caulk and remove the masking. It's also good to check that the lid screws into the housing smoothly before the caulk fully cures.

sm



Edited by Dogboy on May 17, 2018 - 09:56 AM.