This page description is for Marlon - Forespar & Trudesign thruhull / valve backing plates. See menu option for both Groco and Buck Algonquin Flange Valve line and thru hull backing plates.
We manufacture these in house with 1/2 inch thick Extren 525 fiberglass. We have stock available for Marlon, Groco, Trudesign and Buck Algonquin valve and thruhulls. Buck Algonquin and Groco valves use the same size and bolt pattern backing plates. We cut and drill these on a cnc router.
Extren 525, see Strongwell.com is water proof, fire proof, mass produced polyester fiberglass sheet. Epoxy, Polyester and Vinyl ester resins will bond to it. 30.000 PSI compression and tensile strength.
The Seacocks and thruhulls can be purchased from West Marine and Defender.com and many others.
Install as a dry fit first. If the backing plate needs to be sanded to fit the curvature of the hull, orientate the valve correctly first and mark off the correct section to sand with very course sand paper or file. A belt sander works well.
| Product Name | Fits Marlon Seacock Series 93, no flange so no bolts |
OD | ID |
| MA93 – 1 | 1/2", 3/4" | 4.125" | 1.1" |
| MA93 – 2 | 1.0", 1.25" | 4.75" | 1.6" |
| MA93 – 3 | 1.5” , 2.0” | 5.25” | 2.125” |
The Marlon 849 Series 1/2" and 3/4" backing plate holes are tapped with 1/4"-20 threads.
The 1.5" plates are tapped for 5/16 - 18 threads.
| Product Name | Fits Marlon Seacock Series 849 |
OD | ID |
| MA849 – 1 | 1/2" |
4.5" | 0.825" |
| MA849 – 2 | 0.75" |
4.25" | 1.03" |
| MA849 – 3 | 1.5” | 6.875" | 1.86” |
Order here or call us to order at 304 723-4553
Marlon 93 Series with no holes
Marlon 849 Series
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