CONTINUOUSWAVE

Q1: when a 170 MONTAUK boat is at the dock, should the drain plug in the stern sump under the plastic grate forward of the outboard engine be removed?

Q2: when a 170 MONTAUK boat is at the dock would the stern sump pump be switched to OFF in order to prevent draining the battery?

DRAIN PLUG ADVICE FROM OWNER'S MANUAL

I understand one drain plug is for the anchor locker drain. A second drain plug is for the storage area in the bow. At PAGE 3.1 the owner's manual states that when atthe dock remove both the sump drain and the garboard drain at the bottom of the boat. This does not make sense to me because it [perhaps means the garboard drain] is not accessible. I infer that Boston Whaler meant to to say to just remove the sump drain.

Q3: in what situation would the garboard drain need to be removed, if ever?

The garboard drain seems pretty important since it is so low but the only one [of the four drain plugs] that fits is just a plastic screw cap with a gasket. The other compartments have drain plugs that expand when you close them and are much more secure.

Q4: which drain plug is used with the garboard drain?

There is literally no explanation in the manual regarding which drain plugs are used with which drains.

ASIDE: this forum has been very helpful in other aspects of ownership of the boat.

BACK STORY

I am a new boater. I bought a 2020 170 Montauk about the time that the pandemic began [perhaps means March 2020]. I used the 170 MONTAUK for one year, but then because the marina closed, the boat had to be stored. [During or before storage] four drain plugs were removed. In June 2022 the boat got a "a mechanical inspection."

I have read the 170 MONTAUK Owner's Manual; I have searched this forum.

The name "garboard" identifies the bottommost plank in a boat hull. So the garboard drain would be a drain that is located at the lowest part of the hull. In the case of a small outboard engine boat, the "garboard" drain is usually at the transom, on centerline, and as deep as possible.

Because you mention that one of the plugs is a "screw" type, I infer that the garboard drain has a threaded socket for the drain plug to thread into. On that basis, the plug with threads is the plug to use for the drain that has a threaded socket.

The path of the deep transom drain is usually horizontal, not vertical like the other drains. Because the drain is well-below the waterline and leads horizontally to the interior space above the inner liner fo the double bottom hull, if that drain were open the result would be the boat would begin to drain the sea into the interior spaces of the hull above the hull liner until the water level rose to match the waterline of the hull.

I doubt that there would be advice given to remove the garboard drain while the boat was in the water. If the manual instructs you to do that, you should contact Boston Whaler customer service. Ask them to review the written advice in the manual with you to see if they are reading the instructions as you have read them.

cvinson wrote:Q1: when the boat is at the dock, should the drain plug in the stern sump under the plastic grate forward of the outboard engine be removed?

Depending on the weight aboard and the distribution of that weight, a Boston Whaler boat will typically be able to have the aft cockpit sump drain open to the sea when the boat is at rest and the static trim on the boat is not too far down by the stern. With the aft cockpit sump drain open to the sea, seawater will flow into the sump. The water level in the sump will rise until it matches the waterline level of the hull.

Before leaving the boat afloat with the aft cockpit sump drain open to the sea, test that configuration. Observe how much water flows into the sump and the level it rises to. Do this while you are not standing at the stern, as your weight will alter the boat trim. If the water remains contained in the sump--the best outcome--or if the water only rises to overflow the sump slightly and spills over into a confined area near the sump, then leaving the boat unattended with the aft cockpit drain open to the sea is possible.

If the water level with open drain rises and water overflows the sump and collects on the cockpit deck, and if the boat is left unattended for long periods, the sitting water in the deck could begin to exhibit some plant growth or at the least turn green with algae. This may not be tolerable for many boat owners.

cvinson wrote:Q2: when the boat is at the dock would the stern sump pump be switched to OFF in order to prevent draining the battery?

If the aft cockpit sump pump is left with the setting at AUTO, the pump will continually try to keep the sump water level below the threshold level for the pump control mechanism. If the drain to the sea is plugged, the only path for water to enter the sump will from rain (or some other leaking of water into the hull from another location).

How often the sump pump will run will depends on the control mechanism. If the control mechanism is a float switch in the sump, the pump only runs when the sump water level rises above the ON-threshold of the float switch. The pump will stop running as soon as the pumping action lowers the water level in the sump below the OFF-threshold. Again, you should test this automatic operation of the float switch and pump to verify that the system will operate as intended, that is, the pump will run, drain the sump, and stop. All sorts of problems could prevent this from occurring, so actually checking that the automatic control works as intended is essential.

Depending on exactly what compartment is drained by the "garboard" drain, leaving the drain open might not be a problem if the compartment that was being drained was a deep sump compartment whose wall rose well above the waterline of the boat. You could experiment on your boat to see what will happen if you leave the garboard drain open, but I would conduct that experiment in shallow water while you stand next to the boat ready to put in the garboard drain plug if things go badly.


If the control mechanism is integral to the pump, the pump may have an automatic operation that requires that the pump spontaneously turn on and try to pump water out of the sump at periodic intervals. The control mechanism interprets the presence of water as a load on the pump motor. A loaded pump motor will demand more electrical current than a pump motor that is just spinning its pump impeller in the air. If the pump assess that there is water in the sump based on the electrical current being demanded by the pump motor, then the pump motor will continue to run until the water is removed from the sump to the point that the pump impeller is now operating mostly in air and its current demand has decreased. At this point the pump goes back to the OFF state, and waits for the preset interval to time out before starting again. This cycle repeats until the battery is exhausted.

If the aft cockpit sump pump motor control is set to OFF then the motor won't run at all, until the control switch is moved back to ON or AUTO. If the pump control switch does not have three positions--OFF/AUTO/ON--then read the manufacturer's instruction about how the pump electric motor is controlled by a switch.

cvinson wrote:Q3: in what situation would the garboard drain need to be removed, if ever?

A deep transom center drain just above the hull bottom would typically be removed when the boat was not in the water, for example, then the boat is on its trailer or on a storage rack or on a boat hoist. When the garboard drain is removed at the transom, the boat should be oriented with the bow higher than the transom so that any water in the boat flows to the stern.

Typically a drain that is plugged from the exterior of the hull would only be removed when the boat was not in the water. For a 170 MONTAUK to be sitting on its trailer for extended periods would be very common, and the garboard drain threaded plug would be removed to open that drain path to the air and ground, again, allowing for the fore-and-aft orientation to have the bow higher than the transom.

This is fantastic and answers all my questions.

I did the test you described and the sump fills just up to the base when there is no plug in. You do have to turn off the battery otherwise the automatic function turns on.

BTW, the specific warning the manual on page 3.1 is (matching caps):

CAUTION

ALWAYS remove your garboard/sump drain plug if your boat is moored or out of the water to prevent flooding of the cockpit.

What I understand now is the manual should say:

Remove the threaded garboard plug when the boat is out of the water

and

Remove the sump drain and turn off the battery switch when moored OR rely on the automatic sump drain function, keeping in mind battery use.

Thanks.

The real answer to the concern about removing the garboard drain plug can only be known by understanding what compartment or sump will be drained--or filled if the plug is removed. If the "garboard" drain only drains a deep sump whose walls will rise well above the waterline, then if the plug is removed all that occurs is the sea will drain into that sump and fill it to the boat waterline.

I would not expect that everyone who owns a Boston Whaler boat routinely leans over the transom, reaches down into the water, and unthreads the drain plug of a deep transom centerline drain--if the boat actually has one.

The instructions in the owner's manual suggest that some harm may occur if the drain is kept plugged and the boat can collect rain water in the cockpit. I would expect that the cockpit sump with open drain should handle that, but there may be some arrangement in the boat's structure where water could collect and NOT be able to flow out the cockpit sump drain BUT COULD flow out the deep garboard drain. As I suggested, this ought to be looked at with some careful scrutiny before tossing out the manufacturer's advice.

ASIDE: for several years I made my living writing technical literature or editing technical literature. Removing ambiguity in any instruction is important.

I appreciate this discussion. I have a 2019 150 Montauk and have been baffled by the same information in the owner's manual at section 3.1 regarding removing the sump drain plug while moored.

Section 2.7.1 discusses through-hull fittings and states:

Any fitting that is underwater needs to be plugged or the seacock needs to be closed.

There are two drains aft. One is in the sump with a pump.

Q5: is this the "seacock" mentioned in the owner's manual?

There is a second drain under the boat which is clearly underwater. The plug is a screw-type.

Q6: is this screw-type plug the harbored plug?

While the boat was on a mooring in the summer of 2022 I have both drains plugged.

In October 2022 the boat was hauled out.

If I'm following this conversation, then it would seem as long as I kept the drain in the sump with the pump closed, then I could (or should) remove the garboard drain plug.

When I removed the harbored plug after trailering, water came out. Somehow water got into the boat.

Please give a URL to where readers can view the owner's manual for the 2019 150 Montauk boat you asking for advice regarding the drains.

A large selection of owners manuals for Boston Whaler models after about 2010 is available on the Whaler Resources page.

Here is the link to download the manual in question.

https://www.bostonwhaler.com/content/dam/boston-whaler/technical/resources/150_Montauk_OwnersManual_2019.pdf