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1985 MONTAUK 17 Drains and Waterline

Posted: Thu Jun 30, 2016 2:44 am
by swiggy
Hi guys, first post here. I just picked up a Montauk 17 hull. Maiden voyage a couple days ago, and I went out without a plug in the sump area drain. I, seemingly mistakenly, believed these boats would take on at most a couple inches of water with no weight onboard. There was just me and a 6hp kicker I was using, as the main motor is still a project.

I just launched, then tied up, and [the MONTAUK 17] seemed to be taking on quite a bit of water. After 30 minutes it was probably about a foot deep, with the gas tank and paddles floating round. I pulled out [the MONTAUK 17] and again the water poured out. But my boat also has one of the brass bilge plugs that I don't see on other Whalers like mine. There was a lot of water in there when I pulled the plug. A lot, like it drained for 5 minutes just pouring out gallons from there.

Is that the hull area on a Whaler?

It is to the left and below the sump drain, but not right at the bottom of the boat. Seems to go up a narrow channel from there, doesn't look like open hull area.

I'm at a loss as to how that much water entered what I presume to be the foam-filled bilge area. I'm sure there are some screws needing Sikaflex, but it was a lot of water after only 30 minutes.

Is there another void that is ok to be filled with water like this at times?

Could this plug drain somewhere other than the hull itself?

Boat didn't seem to sit that low in the water until it took on water. Bottom paint line was just out of the water. I re-applied the bottom paint myself. The hull is in great shape, has no damage, and is definitely not leaking through.

I haven't really been able to figure this out from looking at diagrams of how the boat is constructed. I don't get how I could fill that area with water so fast.

Re: 1985 MONTAUK 17 Drains and Waterline

Posted: Thu Jun 30, 2016 9:18 am
by jimh
The hull of a Boston Whaler MONTAUK 17 has two laminated parts: the hull and the deck. The space between them is filled with foam. The only internal space in that foam-filled inner hull area is the rigging tunnel, which runs from the small cockpit sump at the stern to under the console. This tunnel is a tube--probably PVC pipe--with a diameter of perhaps 4-inches and a length of perhaps 8-feet. The volume of water that could be contained in this tube is thus:

Volume of cylinder = πr²h, where r is radius and h is height

r = 2-inch
h = 96-inch

Volume = 4 ×96
Volume = 384-cubic-inches

1-gallon of water = 231-cubic-inches

So at most the rigging tunnel tube could contain 384/231 or about 1.7 gallons of water.

The small cockpit sump in the stern should have a through-hull drain to the sea. The drain runs aft and goes out the transom below the water line to starboard of the keel centerline. (Please note that when giving directions on a boat, the athwartship directions are given in port and starboard, not left and right.)

The transom splash well should have two drains. When the boat is at rest in its static trim the drains should be just at the water line.

For advice on how the drains work and if they should be plugged, see the owner's manual. If you don't have the owner's manual, I have created an on-line copy in HTML. See ... drainTubes

The cockpit sump drain is usually plugged by inserting the drain plug at the sump in the cockpit. It is unusual to use a plug on the exit of the drain at the transom below the water line. The transom splash well drains are normally never plugged.

A MONTAUK 17 hull with only a small 6-HP engine should be very buoyant and its static trim should be quite high in the stern. You can make an inference about where the water line should be by looking at the owner's manual section on bottom paint. See ... tml#bottom

Note the comment in the drawing: "Water line crosses transom from chine to chine."

Here is a good view of a classic Boston Whaler MONTAUK 17 with a modern 90-HP engine, showing the static trim and water line:

Note the location of the splash well drains relative to the waterline; the drains are an inch or two above the waterline. Note the location of the hull chines at the transom relative to the waterline; the chines appear to be almost clear of the water at the transom. This is a good example of how a classic Boston Whaler MONTAUK 17 hull should float at static trim with no one aboard.

Re: 1985 MONTAUK 17 Drains and Waterline

Posted: Sun Jul 03, 2016 3:05 pm
by swiggy
Hi Jim, thanks for the detailed reply!

I've attached an image that hopefully better illustrates my concerns. Water drained from the metal plug for quite a while, certainly more than a couple of gallons. Is that draining the area between hull and deck? And does this mean my hull been modified?

Re: 1985 MONTAUK 17 Drains and Waterline

Posted: Sun Jul 03, 2016 8:52 pm
by jimh
Show a wider view of the boat transom as seen from astern.

Re: 1985 MONTAUK 17 Drains and Waterline

Posted: Mon Jul 04, 2016 1:58 pm
by swiggy
Ok I will do, when I am home tonight. If it helps for perspective then that thru hole (without brass plug) is the dead center hole that goes through to the sump. The brass plug is to the port side of the hull

Re: 1985 MONTAUK 17 Drains and Waterline

Posted: Mon Jul 04, 2016 4:26 pm
by jimh
On the basis of you further description, I do not think that brass fitting to Port of keel center on the transom well below the waterline is an OEM fitting. Compare with the hull shown here:

What does that unusual brass fitting lead to? To what sort of sump or hose does it connect?

Re: 1985 MONTAUK 17 Drains and Waterline

Posted: Mon Jul 04, 2016 5:16 pm
by swiggy
What does that unusual brass fitting lead to? To what sort of sump or hose does it connect?

Good question. I was hoping someone would be able to tell me. It is hard to see in there, I shined a light up and it looks similar to the thru hull cavity from the sump, but I can see maybe 4-5 inches in at most. There is certainly no other 'end' to it unless it is really well hidden

From looking at diagrams of the whaler construction I don't see where it can lead other than into the hull itself.

Re: 1985 MONTAUK 17 Drains and Waterline

Posted: Mon Jul 04, 2016 9:29 pm
by Oldslowandugly
Wow. That is a strange item. It looks like a decent grade marine thru-hull, but attached with Home Depot deck screws. Maybe there was [and still is] water in the hull, and that is how someone rigged a drain. The OEM drain looks pretty beat up, too. And an attempt was made to seal it up with something.

Why not get the proper plug, insert it, and test on the water again?

If water still gets in then the OEM drain can be repaired, But I would seal that other opening for good with fiberglass or Marine Tex.

Re: 1985 MONTAUK 17 Drains and Waterline

Posted: Tue Jul 05, 2016 6:20 am
by jimh
If the non-OEM, added hole in the transom leads to nowhere, it makes no sense, except as some prior owner's misguided notion of how to let water soak into the interior foam, or, perhaps, how to let water out of the interior foam.

With the boat out of the water, presumably on its trailer, orient the boat so the bow is elevated with respect to the transom. Let any water in the hull drain out of both holes in the transom until they dry out.

Find a plug for that added hole. It probably has some sort the thread-in plug.

Inspect the OEM drain, the one on keel center. Make sure the drain has a brass tube liner. See the FAQ on repair of hull drains at:

Q12: How Are Drain Tubes Replaced?

Once these two below-water-line drains are repaired or plugged, carefully inspect the hull for any sign of a poor repair to hull damage. Properly repair any hull damage you find.

Put the boat back in the water. Let it soak for a few hours. Haul it out, remove the plug from the non-OEM drain, and check for any water in the hull interior. If you find water, something is letting water into the hull. Look for the path.

If you find no water, then consider repairing that hole, removing the brass drain outlet, and repairing the laminate and gel coat to completely seal it up for good.

Contact a previous owner to ask what he was thinking when he installed the drain.

Re: 1985 MONTAUK 17 Drains and Waterline

Posted: Tue Jul 05, 2016 11:50 am
by kwik_wurk
Can you send a picture of the entire transom, and with a stick (or similar) to measure how far that hole goes. I am sure you could fish a coat hanger or something to figure it out.

And the [center line] drain looks a little "patched", to say the least.