The second one from left to right is the only one I'm currently plugging. Is it alright not to close the other three?


The boat hull is MAKO 86 23 feet . The boat is not currently sinking, but every 10 minutes I can hear the bilge pump pumping water (Like a jar of water) outside the boat. This is all new to me. I only know is that the second hole must be plugged before going to the water, but what are the other three for?

It is an outboard , center console and it also has a living well. I never use the living well. It always empty. The one I plugged each time I go into the water is the bilge drain. If not plugged the boat would sink. The other three I believe are called thru hull fittings. The other three I don’t understand the usage of them, I'm also suspecting that water is coming through them into the boat causing the bilge pump work every few minutes

  • Does the boat sink if the holes are not plugged? If no why? And when you know why there is your answer. Voting to close as too broad, there is not enough info to answer this question. I will retract my close vote if the question is updated with information about what is on the other side of those 'holes'. Nov 26, 2018 at 13:23
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    I only know is that the second hole must be plugin before going to the water, Why?
    – user15958
    Nov 26, 2018 at 21:01
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    Hi! Thank you for the extra information! As you can see, we put some into the question to make it more complete and because comments get deleted. From now on, you can do it yourself, using edit. We're different from some other systems. Check out the How to Ask page in our help center to learn, and if you have any questions about how we work, do leave us a comment and we'd be happy to help! Nov 26, 2018 at 22:09
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    Have you talked to a dealer of this kind of boat? I think this kind of thing is best answered by knowledge not experiments. That said—have you tried to put water in different parts of the boat with a hose to see if it comes out of those holes?
    – mmcc
    Nov 27, 2018 at 3:33
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    I have retracted my close vote. While more pictures and information would allow for a better answer, this sufficient info now to provide a probable answer. Nov 27, 2018 at 14:45

2 Answers 2


Based on the information available in your current question. There should be hoses attached to the three 'holes' you don't regularly plug. Inspect all the hoses from all the 'holes', repair or replace as needed.

One of the 'holes' should be where the bilge pump ejects water.

The other two 'holes' could/should be for water intake and output for the live well (fresh water to keep fish alive when you catch them)

You should be able to identify the bilge ejection port, while the boat is on the trailer, use a garden hose to put some water in the bottom of the boat and turn on the bilge pump. Never plug this hole, you will burn out your bilge pump.

Assuming the other two, are for the live well, and that you are not able to track them visually to confirm. You probably need to take your boat to a boat mechanic to problem solve and address.


A 23 foot hull might be capable of using an inboard motor, in which case two of the holes could be for cooling water.

Boats are usually designed to be maintained. You should be able to get to the inside face of the transom fairly easily.

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