Thruhull backer blocks

[dakno]

Hello all. I have a 08 H41 and the plywood backer blocks for the genset and engine thruhulls are in poor condition and need replacing. It looks like the area where the seacock/strainers are located is in a inner hull? I am wondering what type of connection there is between the inner hull where the seacock is and the outside of the outer hull where the intake is. Have any of you changed either the backer block or the seacock? Or in the strainer area is that the actual hull, not a liner?

 

[smokey73]

It's hard to imagine that a seacock would be on an "inner hull" but I guess anything is possible. Not sure why a builder would do that though and it would add a lot of complexity as well as opportunity for failure so I'd bet money that the seacocks are on the hull itself. With that said, I have a couple of plywood backers that I need to replace at the next haulout. I've been watcing them closely so I'm watching this thread to see what other's recommend for a backer.

 

[dakno]

The yard where my boat is recommends epoxy coated marine ply for the new backer blocks, what was there was raw plywood.

 

[Rich Stidger]

When I replaced my galley thru-hull and reworked my seacock a couple of years ago I used a circle of 1/2" fiberglass epoxy board. I don't know the source because a friend who was re-doing a few of his thru-hulls gifted me this piece. I would expect any decent boat building business to have this. I think I remember that my friend needed to buy a 2-foot square piece that yielded many thru-hull backup bases.

After grinding the mounting surface to get to clean bare fiberglass I bedded it with thickened West System epoxy. I also added the pictured Groco adapter that adapts the NPS straight threads from a thru-hull to the NPT tapered threads on the ball valve. Slick installation; I will do it again if needed.

 

[jssailem]

Very nice set up Rich.

 

[Rich Stidger]

I checked the SBO store, but I did not find the board.
But it is at Jamestown Distributors-

 

[seadaddler]

I replaced all my backing plates on my 2007 H-36 an$ were coming apart so I used
marine ply wood coated with expo you.

 

[chuckwayne]

As far as I know all Hunter hulls are solid glass below the waterline; I'm positive that's true for the 41DS.

 

[Mechone]

I checked the SBO store, but I did not find the board.
But it is at Jamestown Distributors-
View attachment 161394

Did mine exactly the same ,the board is G10fr4 Garolite and is available in any size or thickness from Mcmaster Carr in U.S and it is also what is used for your drive shaft tube .I used 1/2 " for my thru hulls and transducers.Used west epoxy mixed with 404 .

 

[dakno]

Well it looking like no 2004 and up owners have replaced there engine and genset thruhulls? Why do I have to be the first? It might be worth a call to Hunter helpers on this site. I will post what we figure out.

 

[Gunni]

FYI; GROCO now makes a custom backer plate with threaded inserts for their thru-hull. Better than wood, and you don’t have to eat up saw blades cutting G10.
https://www.groco.net/products/valves-seacocks/flanged-valves/backing-blocks

 

[dakno]

We have replaced ac, genset, and engine backer blocks with epoxy coated marine ply. the remaining thruhull backer blocks will be sanded , taped off, and coated with multiple coats of epoxy. I may even drill 3/16 " holes in the blocks after epoxying and fill the holes with more epoxy. All the original blocks appear to have been raw plywood. I would recommend checking your blocks and if they look like raw ply, coat with epoxy to extend life.