Sea-Dog screw-out inspection plates may look alike, but the nominal size, outside flange and installation opening differ. Four MPNs here cover two diameters in white or black. Before replacing a damaged plate, measure the existing deck opening and flange and identify the screw-out fitting rather than assuming a similar round cover will fit.
Identify the existing flange diameter
The small white 337140-1 and black 337145-1 have matching nominal size and mounting dimensions.
The larger white 337160-1 and black 337165-1 have the same dimensional group but are not drop-in replacements for the smaller plates.
Compare the manufacturer's A–D measurements
The dimensions below are Sea-Dog's labelled A, B, C and D measurements. For replacement, compare the original opening, flange and fastener circle with the manufacturer's drawing.
| Display MPN | Colour | A · nominal size | B · outside flange | C · drawing | D · drawing |
|---|---|---|---|---|---|
| 337140-1 | White | 4-7/16 in | 5-3/4 in | 4-1/2 in | 5-1/8 in |
| 337145-1 | Black | 4-7/16 in | 5-3/4 in | 4-1/2 in | 5-1/8 in |
| 337160-1 | White | 6-1/2 in | 8-1/8 in | 6-1/2 in | 7-3/8 in |
| 337165-1 | Black | 6-1/2 in | 8-1/8 in | 6-1/2 in | 7-3/8 in |
Dimensions in inches. These are Sea-Dog's manufacturer-labelled measurements for the exact display-pack MPNs; do not use a column as a cutting template without the maker's dimension drawing.
Inspect the seal and deck opening
Inspect the threaded lid and sealing ring, and measure the mounting-hole positions before deciding whether to replace the entire plate. The screw-out plate must close correctly and sit flush against the mounting surface.
Sea-Dog instructs owners to clean screw threads with warm soapy water, lubricate with petroleum jelly or PTFE/Teflon grease, and avoid acetone or strong solvents. Do not force a crossed-thread lid. Confirm the existing cover's design before selecting a replacement.
A black lid matching the old colour is not sufficient identification; the base and screw pattern matter just as much.
Find the original Sea-Dog MPN
Select the exact number to review its current product listing and availability.
Sea-Dog 337140-1
White smaller flange; nominal size 4-7/16 in, outer flange 5-3/4 in.
Check exact part and availability
Sea-Dog 337145-1
Black smaller flange; nominal size 4-7/16 in, outer flange 5-3/4 in.
Check exact part and availability
Sea-Dog 337160-1
White larger flange; nominal size 6-1/2 in, outer flange 8-1/8 in.
Check exact part and availability
Sea-Dog 337165-1
Black larger flange; nominal size 6-1/2 in, outer flange 8-1/8 in.
Check exact part and availabilityOther Sea-Dog deck hardware references
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