Scupper Effectiveness

[Jim Cooper]

I'm looking at installing transom scuppers w/flapper but am curious if the flappers truly keep out unwanted water when several people are standing at the transom or when launching the boat at a ramp. I am looking at the Marine East 2"x6" oval scupper and Centek 3" round scupper. I can see where a following sea wave will "push" the flapper closed but while the boat is at rest with a few fishing buddies at the transom is a concern of mine. Do the flappers really stay closed?

 

[RT Firefly]

Greetings,
Mr. JC. Get skinnier buddies.

 

[Unclematt]

The boats I have had that had them did not keep the water out.

 

[Delta Riverat]

Yeah, they are better at letting it out than keeping it out.

 

[mvweebles]

Common for a barely taught bungee cord to bias the door closed. I can't find a picture but the bungee needs to be as long as possible to allow maximum stretch. A small padeye on the door with the bungee terminated on inboard side. Small diameter bungee (1/8"??). Ends can be terminated with crimp eyes used for electrical connections (sample pic attached)

Peter
View attachment 130500

 

[Jim Cooper]

bungee idea is interesting...I was actually thinking of small magnets affixed with epoxy coating.

 

[koliver]

By definition, a scupper is to allow water to flow from a higher level (deck) to a lower level, (outside water level). Makes sense that they are not designed to protect that same deck from outside water. The presumption will always be that the deck is above the outside water level. Reverse that and you can rely on the scupper to indicate a condition that needs attention.

 

[Gdavid]

By definition, a scupper is to allow water to flow from a higher level (deck) to a lower level, (outside water level). Makes sense that they are not designed to protect that same deck from outside water. The presumption will always be that the deck is above the outside water level. Reverse that and you can rely on the scupper to indicate a condition that needs attention.

That is pretty easy to maintain on a 44' boat, but on a 30' boat like the OPs, it is pretty easy to have the deck below the waterline as 3 guys are landing a fish. Allowing water to enter via a scupper will only exacerbate the problem. Raising the deck also raises the CG, so not always an option on a smaller boat.

It is pretty common for CG inspected charter boats to have bungy cords on the flaps for the freeing ports, the requirement is for 12' of free board from the waterline to the deck deck/ceiling but following waves when trolling can splash above this and lead to wet decks and shoes, even on 45' boats. The freeing ports size requirements are dictated by the cockpit volume and can end up being really large on downeast and deadrise style boats.

 

[C lectric]

Scupper flaps will not seal water out of the deck if the boat is loaded to the point that water can backflow.
THey are intended to keep water from backflowing onto the deck while the boat is travelling. Even then if the boat is overloaded enough they may not do a good job.

 

[Gdavid]

The small ones with captive ping pong balls work when they are clean, unfortunately they are rarely clean. On commercial RIBS used in Law Enforcement, SAR, etc. some have sections of rubber hose, large diameter but thin walled that collapse on themselves, works like a duckbill valve but can be tied up above the waterline if the situation requires it.