Bigger Scuppers

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The fact that no one responded indicates that you may be breaking new ground with this project.

You might try the question over on ClassicMako (for Mako) or ContinuousWave (for Boston Whalers). Both sites have folks who have completely restored old boats, replaced transoms, and done other major mods.

Whatever you decide to do, please post pics. :D
pelagic2530":29ny5zzb said:
... want to upgrade the scuppers ... to a bigger size, hopefully 6" by 18". has anyone done this?
Need to? Probably not. Want to? Yes I do. But 6" x 18" :?: , man that is HUGE :shock: !

Now ... why? Here's my reasonings. Reason #1 - My vessel is a '92 vintage and I have seen more than one brass scupper on a transom fail in my life, even when they look good. I even went so far when I had access to a machine shop (GE trained machinst) to make up one of those install tools that's flares over the scupper on the 'non-flared' end as you buy them in marine stores. Reason #2 - I agree with you ... a 1" scupper is just too darn small! Heck, in my youth I could piss more water than those can drain!

However, you need to keep in mind the design of your existing scuppers first!


See that well :?: about 5-6" wide from Megabyte's 2520? Are you going to cut just that area out or cut above it?

I realy think you need to do some thinking first, and if it were me, I would NOT cut into any surrounding area other than the transom itself ... just my $0.02.

What I am looking at are 2 options. Option (A) will be to start at the same level of the 'bottom' where the current scupper is now and drill a 3"+ hole, so the bottom of both holes start from the same level. Into this I will epoxy a 3" diameter fiberglass tube from McMaster-Carr. But first, the hole will be heated to warm the raw wood and then thinned epoxy or CPES will be repeatedly soaked into the wood core using a syringe. This gets messy trying to epoxy the top portion of the hole, so have everything well taped off with pastic wrap. I will probably soak the wood about a dozen times or more, until it cannot absorb any more epoxy.

Once it starts to 'kick', I'll add a standard coat (regular viscosity) of Raka epoxy ( Once that cures I'll sand it to fit the frp tube, then will solvent wash off any amine blush and will then glue in the 3" frp tube using a thickened epoxy. I'll most probably use a somewhat easy-to-sand structural/adhering filler, like micro balloons, and not kitty hair or cabosil (not really for strength).

To prevent water from coming in when backing, waves, or a following sea, I will attach Rabud Sea Scuppers (see below) that can handle a 3" outlet to the transom. Make darn SURE you have room for these or other scupper flap with your swim platform or other ... !

See this link, then go to "Sea Scuppers".

Option (B) will be to use a different shaped and LARGER form of fiberglass shape from McMaster-Carr ... but I am not sure of what size. FWIW I have not found a foolproof and reliable scupper flap design thingy that I like except for the ping-pong ball scuppers sold by Rabud and T-H Marine. They are 100% reliable! I like the T-H model even better as the base stays attached to the transom while the cap can be spun off (loosen a set screw) to clean it. Cleaning the Rabuds means you break the seal of Life-Caulk or whatever goop of choice you attached it with.

All deck hardware and screws holes in my boat are wetted out with epoxy when I refurbished the hull, so I am not too concerned about removing it and resealing it. Besides, on my 2520, the scuppers are a good 5"+ above the normal waterline. Replacing these scuppers will be the 2nd to the last piece of non-glass hardware that hasn't been wetted out with epoxy and rebedded since I bought my empty & abandoned hull. The OB bracket is next, but that's another chapter in my 'to do' list.

Run through this ... see if it helps you ... and come back and ask away. Either way, both of us should document this process with photos for posting to the CP archives.

thanks for all the suggestions, DaleH. im actually pretty intrigued by the ping-pong ball type, and i think im gonna go for those. my problem is that the scuppers are about at the waterline as it is, so im gonna have to cut upwards (plus i hate cutting holes in the boat!) thanks also for the tip about soaking the surrounding area w/ epoxy, hadnt thought of that. im not sure whether or not im gonna do the deed when i pull this season, but if i do i'll be sure to post plenty of pics (if i can figure out HOW :D) and document the whole thing. why doesnt the factory just put bigger ones in t start with and save us these headaches?
pelagic2530":jfgugcte said:
why doesnt the factory just put bigger ones in t start with and save us these headaches?

Actually... these days they do.

The newer boats have two of those brass scupper tubes in the transom on each side with a white plastic 'flap' over them on the outside to keep water from coming in.

Next time I have access to one of the newer boats, I'll get you a photograph. :wink:

within several seasons, i replace the scuppers on my parker.....they
simply were inadequate, e.g. a 5/8" hose on full into the cockpit would
accumulate!......allow me to point out a bit of physics (actually, it is
in the realm of physiology, my major at stanford)......the RESISTANCE
to flow of a liquid is the FOURTH POWER OF THE RADIUS......if you play
around with this formula (law of la place, i believe), you find that small
increases in radius create dramatic increases in flow

this is why kids are always "stopped up"!.....or why a polyp, or an
atheroma, or any tightening of any canal is big trouble......for example,
if you have a one inch scupper, multiply half an inch by the fourth power
and get a, do the same with .625......thus, increasing the
scupper from one inch to one and 1/4 inch yields massive flow increase...

i found some pvc 2and 1/2 inch scuppers on a luhrs boat i liked....i
ordered a pair.......putting the sawzall to my transom took some nerve,
i will admit. but i cut upward about 10 degrees into each side well......
i slathered the raw transom innards with warmed west epoxy to saturate
the core, and then slathered the channel with west epoxy thickened with
high density powder to a mayonnaise consistency.....i slid the new scuppers into the channel with west goop exuding all around them......
i cleaned away the excess and let it all set up.......the scuppers have been
watertight and rock-solid for a decade now........they have a flapper which
REDUCES backwash, but some will roll onto the cockpit if i backdown hard
............i can now use TWO 5/8" hoses on the cockpit at once without
any accumulation....mission accomplished........

the ping-pong-ball scuppers are very interesting, and would be much
easier to do (!) than what i did.........but the primary problem i addressed
was the RATE of flow (out), and so i didnt see that they would solve my
particular problem; i needed to CUT OUT the factory scuppers and put
in something with MORE RADIUS=MUCH MORE FLOW........

i am on the abyc study group for scuppers and cockpit design standards......i am trying to convince the abyc to increase, ie only
a 1/4" the minimum size of scuppers for "selfbailing" cockpits......
they have formulae which show for a given scupper cross sectional
area, how long a cockpit of a given cu ft will drain 75% if FILLED TO
THE GUNNELS.......i dont think this is ideal as a criterion for power
boats, ie if you cockpit is full to the gunnels, you are DONE....secondly,
the 25% is likely unmanageable as well, so i would like to see the criterion be fill the cockpit 25% and gauge the time to EMPTY........

this get very much to how safety is designed into (OR OUT OF) a
given boat........frankly, i dont think the scuppers on parker 25` are
of proper diameter, nor do they have proper backflow protection.....
i would like to see parker AND ALL MFRS put in scuppers which let
MORE OUT AND LESS IN.......this can be done and should be done....
i hope i can convince the abyc to step out front a bit more on this.....dan