Flush thru-hulls flange/head size on Catalina 42.

[BourbonS]

Dear Forum,

Could you please kindly help me with this:

I've got my Catalina 42 1992 last November. Besides ...well... "everything else" I am replacing now all thru-hulls and valves.

Previously/originally these were all Forespar Marelon thru-hulls and valves except two bronze on holding tanks macerators outlets.

Without any intent to start another "Marelon vs. Bronze holy war" I'd would like to mention that:
1. All Marelon thru-hulls were in pretty good shape when I removed them.
2. A broken handle on one of the Marelon valves in a process of very careful "exercising" of it and a minor leak as an unpleasant "side-effect".
3. One valve completely broke in half on a very minor force applied while I was removing a hose. (Good for me that this happened while she was on the hard. Otherwise .... <insert your imagination here>...).
4. One Marelon of "93 series" looked good ... but had periodical minor leak on open/close.
5. Bronze valve (I removed one) looks very good. After some exercising/lubing works smoothly. From the inside looks good as well. I don't see any disturbing signs.

So basically Forespar / Marelon valves currently is not an option (or an option that I will consider as absolutely the last one). Except that one "93 series" valve which has two barbs and I need exactly the same. Part number is 931233 which is not available online and should be ordered directly.)

So without Forespar I have these two options left (all 3/4 except one 1-1/2) :
1. TruDesign valves/thru-hulls. For example Ball Valve .75" NPS, Black (gemlux.com) with load bearing collar Small Gemprint Load Bearing Collar ABYC | Premier Marine Hardware (gemlux.com)
2. Groco bronze flanged with the backing plates;

Ordered both to try.

During "dry-fitting" I realized that I feel uncomfortable with TruDesign because that "load bearing collar" completely blocks any access to a thru-hull without complete removal of the valve. Not sure why I don't like this. Probably because of a hypothetical case of a leak between a thru-hull and a hull that I will not be able to temporary fix. Thru-hull flange diameter is 1-2/3'' but Forespar thru-hull fits OK. For now I don't consider TruDesign as an option for now.

With Croco valves I am having another problem: Catalina has the "flush thru-hulls". Only Forespar has thru-hulls with a flange/head of that size (please see the images). Bronze flush (or mushroom) thru hulls' flanges are smaller.

- Forespar is 2.430(61.72mm)
- Groco is 2".

I feel not very comfortable with a smaller one but was unable to find a bronze flush or mushroom 3/4" thru-hull with the similar flange size as Forespar.
Technically Forespar thru-hull looks and feels like has the same NPS thread as Croco flanged valve. Given that Groco flanged valve will be on a backing plate a smaller flange should be OK.... r-r-r-ight ?

So my question is what should I do:
- Use a bronze thru-hull with a smaller flange?
- Use Marelon thru-hulls with a Groco bronze flanged valves?
- Other options ... ?

Any ideas/hints/thoughts/considerations are needed and appreciated.
Thank you.

P.S. Some other related thoughts. I ordered one backing plate from Groco and I didn't like it at all. This is an overpriced cut made of PVC panel that look similar to what I see in Home Depot. I honestly not sure how it will bond to an adhesive but have some doubts about any "epoxy-based" one.
Got these instead Groco Flange Valve backing plate or bronze bolts | eBay instead.

 

[Tally Ho]

Not sure what to recommend on the mushroom fitting…how is the hole size fit in the hull (other than the taper)? If the fitting is close to the size of the hole in the hull, you are probably ok…you can fair the area around the mushroom fitting.

For the backing plate, I read an article about counter-sinking the bolts in the bottom of the backing plate, and epoxying the heads in place so they won’t turn…then adhering the backing plate to the hull, and then mounting the flanged thru hull to the bolts in thr backing plate.

It looks like this, but on your Amazon plates, it appears that the fiberglass is tapped, and studs screwed into the backing plate. I don’t know how strong those 3 studs would be…maybe perfect…but I don’t know. I like the idea of a bolted, pushed up from the bottom of the backing plate and epoxied in place was a stronger solution.

But if others have confidence in the tapped threads in GRP, I could be convinced it is strong enough.

Greg

 

[jssailem]

Looking at your images it appears the concern is the diameter of the flange is an issue. You said there is a 2 " thru hull. From the data on the Groco site... The "C" diameter is 3.9 inches. Is it the flange or the diameter of the thru hull?

 

[BourbonS]

Thank you for your answers.

1. @Tally Ho
1.1 Mushroom 3/4" Groco will work - this is what was previously installed for two bronze valves. They look not that good as the larger "marelons" but so far were OK. (Definitely those have more contact surface than "flush" type.)
2.2 I like "bolted" more as well but those from Groco are brass, not bronze. (Given that they are "sealed" they might be OK ...or might be not - it will not be very easy to inspect. )
2.3. Taped thread with studs - Here they don't see this as an issue. I don't have any useful opinion about this. ("Dry-tested" - looks good to me. (Will have one side with a hole cut-off for a tight space - will try how much torque it will take.)
3.3 You can widen the wholes in the bottom part for inserts/nuts.

2. @jssailem
My apologies if I messed up some images and description.
- Groco bronze thru-hulls are 3/4". (i.e. FTH-750). "C dimension" is 2".
- marelons "C dimension" for 3/4" thru-hulls is 2.430"

-------------------------------

Is it OK to use marelon thru-hulls with Groco flanged valves? Their threads look the same.

 

[jssailem]

Checking with Marelon to see if they recommend a bronze valve on their thru hull, tech support said that you can attach a bronze valve to their thru hull . They recommended you use their valves.

The flanged valve would be critical in my opinion as the Marelon would be exposed to deformation or breakage if standing up above the hull and attached to a valve that the crew believes is stuck and the captain said "Open The SeaCock so we can get underway".

 

[BourbonS]

There are flanged Marelon valves as well. But I am sort of ... not very enthusiastic about the valves for now after two leaking and one broken.
(I've read their Marelon Valves On Bronze Thru Hulls )

As I mentioned earlier their thru-hulls looked pretty good and strong while I was removing them. Actually I had to drill the holes for a big screwdriver to remove some of them. With that "screw-driver-bending-force" applied some of them cracked but IMO it really exceeded my expectations.
So I am OK with it and asking community whether there is anything that I don't know why I shouldn't do Bronze Flanged valves on Marelon thru-hulls.

 

[BourbonS]

Found this. Flange diameter is 2-/1/2". Ordered to try.
...
(I guess this would be a right moment for another "Groco vs Perko vs Buck Algonquin" )