Draining bilge often while on the water?

Hey guys!! Hope everyone’s had a great start of the season!

I’ll try to keep things short. I have a habit of flipping on the bilge pump about every hour or so while on the water. When I do, I usually see about a half gallon of water get pumped out the side (the bilge pumps for about 10 seconds). Water/weather conditions don’t seem to matter. I notice more water when I have been cruising around more at 25-30 mph.

my boat is a 21’ 1989 Celebrity 208 SE 5.7l V8 mercruiser alpha 1.

I have thru hull exhaust.. but idk if that would play into things. I know I’ve heard that I really shouldn’t have to pump the bilge much. I’m worried this could be a larger issue that may eventually effect the condition of my structural wood (although there’s no evidence of that so far)

maybe a leak in the cooling system? What could it be?

Thank you so much! Let me know what you think!

Ayuh,.... The only way to find a leak, is to Look for it,.....

I would imagine you have a leak somewhere around the drive. You really should check out any leak that is happening as it can open up at any time without warning and your bilge pump won't keep up.

That's a LOT of water for that short a period. You'd better find out where the leak is. You'd be in serious trouble if the pump fails.

Jeff

fastjeff said:

That's a LOT of water for that short a period. You'd better find out where the leak is. You'd be in serious trouble if the pump fails.

Jeff

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Are there usual suspects as to where the leak could be occurring? I imagine the leak is happening somewhere in the water cooling loop as that’s the only place I think water enters the engine/boat. Should I also be checking the seal where the sterndrive enters the transom wall? As well as where the thru hull exhaust enters the transom? Just want to narrow things down as I am a novice to this sort of thing.

I also imagine it’s safe to assume I shouldn’t put the boat on the water again until I find this leak, right?

keep it on the trailer and back it into the water. then look for the leak.

Chadbud said:

Are there usual suspects as to where the leak could be occurring? I imagine the leak is happening somewhere in the water cooling loop as that’s the only place I think water enters the engine/boat. Should I also be checking the seal where the sterndrive enters the transom wall? As well as where the thru hull exhaust enters the transom? Just want to narrow things down as I am a novice to this sort of thing.

I also imagine it’s safe to assume I shouldn’t put the boat on the water again until I find this leak, right?

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Based on experience, You are not looking or thinking in the right places.

99% of water leaks for Stern Drive Mercruisers come from the Shift cable bellows or the U-joint bellows.

If you had an incoming cold water supply leak you would/could easily see the water leaking at the rate you describe.


With drive trimmed down on trailer, Turn steering all the way from one side (at a time) to the other and inspect the two bellows I mentioned. Touch and feel for tears or holes. Look close at bellows to see if there is dry rot. On U-Joint bellows look at the two wear points at 3:00 and 9:00 on bellows to see if it has worn thru.




If you cannot see any tears or holes, Put plug in boat, Trim drive all the way up, try if you can to raise the front of trailer as HIGH as possible, several feet up. The object is to fill boat from inside until water leaks outside and you can se where it is coming from.

Note: you do not want to fill inside to high and get starter wet!! so you need to be careful. This means the higher you raise the front of boat the easier to get water to leakage points without getting engine starter wet.
We used to have to do this on boats we could not find a leak visually!

If you don't know when the bellows were done on this, then plan to do them. A couple hundred spent now is cheap insurance against that sinking feeling. Or have an EPIRB on board.

kghost said:

Based on experience, You are not looking or thinking in the right places.

99% of water leaks for Stern Drive Mercruisers come from the Shift cable bellows or the U-joint bellows.

If you had an incoming cold water supply leak you would/could easily see the water leaking at the rate you describe.


With drive trimmed down on trailer, Turn steering all the way from one side (at a time) to the other and inspect the two bellows I mentioned. Touch and feel for tears or holes. Look close at bellows to see if there is dry rot. On U-Joint bellows look at the two wear points at 3:00 and 9:00 on bellows to see if it has worn thru.




If you cannot see any tears or holes, Put plug in boat, Trim drive all the way up, try if you can to raise the front of trailer as HIGH as possible, several feet up. The object is to fill boat from inside until water leaks outside and you can se where it is coming from.

Note: you do not want to fill inside to high and get starter wet!! so you need to be careful. This means the higher you raise the front of boat the easier to get water to leakage points without getting engine starter wet.
We used to have to do this on boats we could not find a leak visually!

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Thank you Kghost, and everyone else!

Forgive me as I'm sure I'm about to sound like a complete idiot.. But I've never noticed the exhaust bellows or any other bellows on the sterndrive. Considering this boat is "thru-hull" exhaust I guess I assumed it was capped? However, I have not inspected closely to observe shift cable bellows or U-joint bellows. From research it seems those bellows would be hidden a bit up inside the sterndrive normally. Still, this kind of setup would still definitely have those right? I plan to run down to the garage tomorrow evening to do just as you said and search for the bellows you described.

I really hope I do find something because I've been meticulously silicone sealing all points where screws/fittings/rails/supportive joints enter the boat hull. I even replaced the speedometer pilot kit on the rear of the boat and sealed it on. I was even considering doing the swim platform supports where they connect to the transom as well!

It sounds like this is definitely a leak coming from the bellows or somewhere else in the transom. My plan is to actually put the boat on the water completely dry in the bilge and then run it at cruising speed with trim slightly up to force any water to come to the bilge. I will have my brother constantly observe the bilge while running to view for leakage points. (this is a lot more realistic for me to do than jacking up the tongue of the trailer until I might observe the leak that way)

Let me know what you guys think! Thank you again for all the outreach and support!

The only difference between thru hull and thru prop exhaust is just that.

The exhaust has water flowing thru it so it has nothing to do with a leak unless the exhaust components in engine area are leaking.

ALL Mercruiser ALPHA boats have both the shift cable and U-Joint bellows and the purpose of those bellows is to keep water OUT of the inside of the boat.

In fresh water use only, the bellows can last up to ten years, In salt water that is much shorter and can need replacement as soon as 3-5 years

Your silicone sealing is a pointless exercise. That stuff will fail in a heartbeat. You should use the proper bedding and sealing products. Simply smearing silicone on stuff does nothing.