How much water in bilge is normal?

Hello Everyone.

I am officially on my journey after looking at three boats this last week. I already can see the dramatic differences between owners of boats. In just three boats I have seen the meticulously well maintained and the I don't care so much maintenance.

This brings me to my question. How much water should be in the bilge? I noticed one boat with a bout 4-5 inches. It was well over the intake propeller. To me, 4-5 inches seems like a lot. I guess it depends on where the float is and when it is set to come on?

Happy Trawling.

Rick

When I bought my boat, it had 4-5 inches and it was determined the bilge pump wasn't working. It is also possible the pump was turned off at the electrical panel.

This is something the surveyor would address and typically the seller is asked to address it as a condition of sale,

Greetings,
Welcome aboard. THIS is too much...

RT Firefly said:

Greetings,
Welcome aboard. THIS is too much...

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that will buff right out on a low tide

HOLLYWOOD

When we bought our boat last year, there was water in the bilge - the broker & the surveyor both said some water was normal. After reading much info on "dry boats" I concluded that any water is bad. So took the false floor up in the bilge, replaced the aft bilge pump with a new one, plus wire. Cleaned the drain channels from one compartment to the other. Out went the water. The shower drains into the bilge. I'll plumb in a drain to the overboard. The less water the better. Someone in TF will more learned advice than I. Keep the thread alive & see what everyone has to say. Good luck, TONTO.

Unless your bilge pump can pump the water overboard and then shutdown, jump off its mount and sponge up any residue, you will never have a perfectly dry bilge. When the pump shuts down, some small amount of water always flows back out of the pump. This is perfectly normal.

As to your question of how much water, anything significantly above the shutoff point of the float switch should be hunted down and addressed. Often air conditioning condensate is routed to the bilge in which case your bilge will never be perfectly dry if the air is running. If showers or sinks drain to the bilge they should be routed overboard or to a gray water tank or you will eventually have a smelly bilge.

Of great importance is how often the bilge pump cycles. You could have a leak and not know it if the bilge pump is continually cycling and pumping it overboard. A counter in the circuitry is a worthwhile investment. If you don't have one, you should be alert to frequent cycling of the pump and determine why it is cycling.

Hope this helps.

Howard

hmason said:

Unless your bilge pump can pump the water overboard and then shutdown, jump off its mount and sponge up any residue, you will never have a perfectly dry bilge. When the pump shuts down, some small amount of water always flows back out of the pump. This is perfectly normal.

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Agreed that a bilge pump cannot remove all the water, but:
1) There should be enough ventilation that unless new water is coming into the bilge the residual water will evaporate. If it isn't evaporating, that humidity is not good for equipment.
2) No water should be entering the bilge in the first place. No hoses should be leaking, shaft seals should not drip, and the cockpit should be 100% self bailing. And the shower should drain into a sump that automatically pumps overboard. The only water I get on my boat is condensation from the ice maker, and I intend to rig up a sump to deal with that.
The pride and joy of having a dry and clean bilge cannot be overstated.

If the water is above the pump switch something needs fixing.

One of my per peeves with most boats is that they don't have a small sump so that pumps can remove most of the water. Instead they have a large area where even 1/2" of residual water is a lot.

Some water is common though we all fight it.

There are a lot of weird things done on boats such as draining AC condensate into the bilge.

That would not turn me off on a boat though I would have the usual suspects, shafts and rudders checked. If water is not continually running in You can deal with it.

Some shaft packing designs are intentionally left dripping slowly while boat is running.

Hey fellas, I was told my shaft seal was to have a drip. Ford Leman engines X 2. I think the mechanic told me about 1-2 every 4 sec or so when in use. Any thoughts? No rude thoughts! This could go south fast.

"1) There should be enough ventilation that unless new water is coming into the bilge the residual water will evaporate. If it isn't evaporating, that humidity is not good for equipment."

I agree that your thinking would be correct in a perfect world.

Where does the dripping from the stuffing box(s) go? On Magic they go into the bilge. Let's assume your bilge pump cycles, and when it shuts down, 8 oz. of water flows back into the bilge sump. Now, take a teacup (8 oz.) of water and set it in your bilge. How long does it take to evaporate?

ALL IN said:

This brings me to my question. How much water should be in the bilge? I noticed one boat with a bout 4-5 inches. It was well over the intake propeller. To me, 4-5 inches seems like a lot. I guess it depends on where the float is and when it is set to come on?

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It depends. (The usual boat answer.)

In a boat with dripless shaft seals, as little as zero. In the same boat with rod holders plumbed directly to the bilge, or a shower sump that often overflows, or one with A/C condensate plumbed to the bilge, a fair amount.

We have three separate bilges, two dry, one (with rod holders) wet.

If the bilge pump can really get all bilge water overboard, dry is often attainable for a while. Most bilge pumps can't actually do that, though, so a puddle isn't unusual, especially in boats without dripless shaft seals.

It depends

-Chris

hmason said:

"1) There should be enough ventilation that unless new water is coming into the bilge the residual water will evaporate. If it isn't evaporating, that humidity is not good for equipment."

I agree that your thinking would be correct in a perfect world.

Where does the dripping from the stuffing box(s) go? On Magic they go into the bilge. Let's assume your bilge pump cycles, and when it shuts down, 8 oz. of water flows back into the bilge sump. Now, take a teacup (8 oz.) of water and set it in your bilge. How long does it take to evaporate?

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Granted, I am talking about a perfect -- but achievable -- world. PSS shaft seals should be 100% dripless.

Old style packing drips as your mechanic said. Gore packing does not drip. You can replace your old stuff easily enough.

This brings about a question I have.When it rains,are bilges supposed to fill with water?A Bayliner cuddy, that I used to pilot,the bilges would fill with water when it rained,even when the cockpit was under full canvas.I never found where the water was coming from.Fortunately,that boat wasn't owned by me.The boat I am planning to build will have wet bilges in the rain as the rear deck will be to close to water line for scuppers.I may raise the deck when I build and add scuppers.

There are more than a few ways water can get into a bilge... some more are through an anchor line hawse pipe or engineroom vents also.....

While it is possible to have a completely dry bilge...it's not the end of the world if it isn't.

Hopefully the water is no deeper than near the bottom of the lowest automatic bilge pump.

Waterlines higher than that suggest someone wasn't paying close enough attention to the boat.

But multiple sources , even condensation inside the hull can lead to water...while a bone dry bilge would be nice...few boats ever attain that status and run just fine for decades.

Any cockpit boat has extra difficulty is keeping a dry bilge because the many hatch seals and drains are difficult to perfectly maintain.

I've got a couple inches of water in the bilge. My cockpit hatch doesn't seal which lets a fair bit in.
My shaft seals occasionally have a slow drip witch I'm not overly concerned about. Better slightly loose than too tight.

Some people have check valves in their bilge pump hoses, but I don't, so there is alway backflow after the bilge pump shuts off.

It also depends on the shape of your bilge. If there is a low point with a small area for the bilge pump suction, you can minimize the volume left behind. If the area is large, there will be a greater volume of water that is difficult to suck up.

I always have about an inch in mine. Small drip in packing for shaft and rudder, nothing to get all worked up about IMO. I like the cycle counter idea and may work one in soon, seems prudent.

I was think about putting a check valve after my pump to keep the little bit of water from draining back after the pump shuts off . Has anyone here ever done that ?

Greetings,
Mr. PM. I would be concerned with the check valve getting stuck either with some sort of corrosion or debris from the bilge and malfunctioning. The LAST thing I'd want is a "clogged" exhaust line from the pump. These sort of "problems" always seem to happen at the worst possible time so totally unrestricted hose for me. As mentioned, a bit of water in the bilge is acceptable.

Thanks RT , I wasn't sure if it was a good idea or not . I can live with a little funky water in the bilge.

Pack Mule said:

I was think about putting a check valve after my pump to keep the little bit of water from draining back after the pump shuts off . Has anyone here ever done that ?

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Check valve on standard centrifugal bilge pump is a bad idea. If the check valve gets held closed by a standing head of water in the discharge line, it may not open on a subsequent start. Since the bilge won't empty, the pump will run until the battery is dead or the motor burns up.

TONTOROSS said:

Hey fellas, I was told my shaft seal was to have a drip. Ford Leman engines X 2. I think the mechanic told me about 1-2 every 4 sec or so when in use. Any thoughts? No rude thoughts! This could go south fast.

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That drip rate seems extremely high to me. I have always heard numbers like one drip every 30 seconds to a minute.

The critical item is not the drip rate but the temperature of the shaft log. The drip rate should be as low as possible while keeping the shaft log cool or at least not hot.

I've always been able to adjust our packing glands (flax packed) so they don't drip at all but the glands remain cold underway. There is a sheen of water around the shaft where it enters the packing gland but no dripping.

However, our vintage of GB36 has two cutless bearings in each shaft log and a cooling water feed from each log's respective engine because of this. So it's possible to run the shaft logs cold with no drip. Other setups can require a drip.

Pack Mule said:

I was think about putting a check valve after my pump to keep the little bit of water from draining back after the pump shuts off . Has anyone here ever done that ?

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Yup. We have a check valve. The pump is in a small sump. With out the check valve, the water that is contain in the hose, when the pump shuts off drains back into the sump and trips the pump switch again. We end up with a continues cycle. It's an easy maintenance item plus we added another float switch up higher to an alarm if the check valve fails shut.

Larry,
If your check valve malfunctions and the alarm is triggered it may be too late to address the situation. I suggest you raise the float switch a bit. Perhaps a piece or two of Starboard under the switch mount to raise the unit some. Then remove the check valve. Just a suggestion. Howard

If I have the right label for this piece of equipment, it is the stuffing box (maybe). It is where the "shaft" comes from the Transmission to a what ever is where the water drips from. Before I left the boat, I tightened the bolts to stop the dripping, placed a note on the throttle to loosen the bolts prior to starting he engines. Sorry for not having a knowledge of the mechanical items. If someone would correct me it would help. TONTO

hmason said:

Larry,
If your check valve malfunctions and the alarm is triggered it may be too late to address the situation. I suggest you raise the float switch a bit. Perhaps a piece or two of Starboard under the switch mount to raise the unit some. Then remove the check valve. Just a suggestion. Howard

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Your right the check valve could fail but some are more reliable that others. I'm using a Groco PNC series that opens at 0.5 psi. No rubber to deteriorate and easily tested/inspected. We've looked at reducing the discharge hose size, adding 2 switches, we can't enlarge the sump. Believe me, If I had a choice, I wouldn't use one, but thanks for the idea.


Groco PNC-Series Pipe Nipples with Check Valve - 1" NPT

TONTOROSS said:

If I have the right label for this piece of equipment, it is the stuffing box (maybe). It is where the "shaft" comes from the Transmission to a what ever is where the water drips from. Before I left the boat, I tightened the bolts to stop the dripping, placed a note on the throttle to loosen the bolts prior to starting he engines.

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At the risk of telling you what you may already know, here is my understanding of the setup.

On a conventional system, the shaft passes through a tube or "log" that penetrates the hull of the boat. There is at least one cutless bearing (a hard, rubber-like collar with longitudinal grooves in its inner surface) centering and supporting the shaft inside the shaft log. This bearing is lubed and cooled by the seawater inside the tube.

Obviously, the log has to be sealed at the engine room end to keep the water from simply pouring in around the shaft. So there is a packing gland at the engine room end of the log that contains a sealing material--- originally flax, but there are newer synthetic sealing materials on the market if one chooses to use them-- that is mashed down around the shaft and against the inside surface of the packing gland.

The mashing is done by the packing nut, which is generally the forward of the two nuts on the packing gland. Tightening this nut compresses the packing material which in turn reduces the amount of water that can leak past the shaft and into the boat.

The nut behind the packing nut is the lock nut. When run forward and tightened against the packing nut, it locks the packing nut in place.

If the packing material is mashed down too tight, it can restrict the passage of water through the packing gland (the drip) and this and the friction of the packing material jammed hard against the spinning shaft can cause the packing gland and shaft to overheat, which can damage the gland and the shaft.

It's a trial and error process to get the packing nut adjusted correctly. Backed off too far and you get too much water coming through into the boat. Tightened down too much, and you get an overheated gland and shaft.

The trial and error adjustment has to be done with the shaft spinning, ideally with the boat underway.

Once the packing nut has been adjusted to the best compromise between cooling and dripping, the lock nut behind the packing nut is run up against the rear face of the packing nut and the two are tightened against each other. Then make one more check of the shaft log temperature to make sure it's still what you want, and that's it.

The above description applies to the basic, conventional packing gland system. There variations on this system, and there are the so-called dripless systems which use a different principle entirely (as I understand it).

Our boat has conventional packing glands but with cooling water feeds from the associated engine.

My bilge's are bone dry, and dusty would be a more accurate description.

Conall
Conall's Boat Build