Raw Water pump leak

junaido · August 03, 2025, 01:31:55 PM

In the start of a weeklong trip and I noticed the bilge pump was kicking on and off. This was after a couple of hours of motoring Further examination showed the raw water pump was dripping steadily. Question: Is this enough of a reason to abort the trip and head home? Or if the bilge pump continues to keep up with the leak can I continue with the trip? Do these leaks get worse quickly to where they are going to overwhelm the bilge pump? The San Juan islands have fluky wind and lots of narrow tidal current passages and I don't want to risk an overheating engine.

junaido · August 03, 2025, 01:40:55 PM

Engine temperature never went over 160 btw and the drip is pretty slow.

Noah · August 03, 2025, 01:59:57 PM

Hard one to give advice on. Risk tolerance is VERY personal. I am not a mechanic so don't know if pump will fail further, seize-up, etc?? I carry a spare pump out of caution. But that's me. Good luck and keep a sharp eye on engine temp and make sure the water dripping on engine isn't causing other engine (belt slip, electrical?) issues.

Ron Hill · August 03, 2025, 02:11:33 PM

Juna : As Noah mentioned keep an eye on the engine temp!! I'd get the pump (probably and Oberdoffer) rebuilt with a new lip seal ASAP - as that dripping of salt water down the front of the engine will eventually rust out a spot in the engine oil pan!! I've seen it happen!!!

A few thoughts

KWKloeber · August 03, 2025, 05:27:49 PM

Note Noah's first sentence.
There's not enough info to make an intelligent call about your risk.

First, (IMO) it's not fathomable that a pretty slow drip would result in the bilge pump noticeably kicking on and off. If that's true, depending on one's personal definition of on-off (1x/min, 1x/hr, 1x/day) and slow (1x/sec, 1x/min) and the bilge pump's "on/off" levels and bilge capacity, there's possibly more going on than a slow drip.

It's simply impossible to provide a meaningful answer. The question is not, "Will she overheat (with a SLIGHT drip)?" - a slight drip will never overheat the engine, or, "So long as the bilge pump keeps up...?".
The question is actually, "What's the risk of a catastrophic failure and be dead in the water?"

One cannot answer that intelligently w/o knowing the source and cause of the leak, condition of the pump, when it was last serviced, and the owner's normal annual maintenance (if it's at all other than, "If there's a leak or failure (the out of sight, and if it's working don't futz with it") approach to vessel preventive maintenance.)

Excuse my soapbox and bluntness, but... These days everyone has to buy the latest communication device for their pocket with the highest resolution camera and video recorder, yet it seems rarely do posts include pictures or vids when asking questions about a problem/switch/leak/equipment/whatever that is specific to THEIR vessel.

Off my soapbox now!

Ed Shankle · August 04, 2025, 04:28:15 AM

Junaido,
You may have 2 separate issues. It doesn't sound like your raw water pump drip would fill the bilge fast enough to trigger the bilge pump frequently.
Determine if the bilge water is fresh or salt. If fresh it could be a leak in your fresh water system. Is the water pump under sink cycling at all?
Is the stern bilge exit going below the water level when motoring? Could be suctioning water back to the bilge.
How much water is flowing back to bilge after it pumps out? Could be enough to trigger the pump to cycle on again.
A few things to consider...
Regards,
Ed

Jim Hardesty · August 04, 2025, 04:52:53 AM

QuoteYou may have 2 separate issues. It doesn't sound like your raw water pump drip would fill the bilge fast enough to trigger the bilge pump frequently.

My thought also. Look for other, more substantial, leaks.
Jim

junaido · August 04, 2025, 09:18:55 AM

So after I posted the original question I ran the engine at slow speeds (1200-1400rpm) and the drip didn't trigger the bilge pump even after half an hour of running. I also noticed a bunch of hot steaming water in the bilge after I washed my hands. My first thought was that there was something wrong with the exhaust system but that seemed ok, but then I looked at the water heater under the galley sink and it was hissing and dripping water. Not sure if that is connected with the water pump issue? I have uploaded a video on YouTube that shows the drip. I checked the impeller about a month ago and it didn't seem like it had any broken vanes so I left it alone.

junaido · August 04, 2025, 09:28:24 AM

https://youtube.com/shorts/RLdvceTYFqc?si=vSrqwD73vXLOFSiG

Stu Jackson · August 04, 2025, 10:32:06 AM

Quote from: junaido on August 04, 2025, 09:18:55 AMSo after I posted the original question I ran the engine at slow speeds (1200-1400rpm) and the drip didn't trigger the bilge pump even after half an hour of running. I also noticed a bunch of hot steaming water in the bilge after I washed my hands. My first thought was that there was something wrong with the exhaust system but that seemed ok, but then I looked at the water heater under the galley sink and it was hissing and dripping water. Not sure if that is connected with the water pump issue? I have uploaded a video on YouTube that shows the drip. I checked the impeller about a month ago and it didn't seem like it had any broken vanes so I left it alone.

You have two different issues.

1. Leaking raw water pump - This means the SEALS inside the pump are failing. When they do, they leak through the weep holes, which are telltales to tell you that you have to replace the seals. There is a how To in the 101 Topics: Oberdorfer Pump Rebuild 101 - http://c34.org/bbs/index.php/topic,6766.0.html [Link added to main page of C34 Tech wiki]. If it is a slow leak, finish your cruise, but fix it soon or else water can mix with engine oil.

2. Water heater pressure relief valve - If you keep the heater plugged in all the time, this valve can "pop" because the water gets too hot and expands. Only 30 minutes is needed to get water hot. Then turn off the breaker. Flip the lever on the valve to release pressure. Sometimes crud gets stuck inside the valve, repeated flipping may clear it, if not get a new valve at a hardware store.

Noah · August 04, 2025, 11:21:35 AM

Normally I taste the water in the bilge to determine if it is fresh or salt. If this case however, it seem like you may have both a freshwater issue with hot water tank and a salt water issue with engine raw water pump. In addition to the stuff Stu mentioned about pressure relief valve, I would thoroughly inspect hot water tank to check for other leaks (hose clamps etc.). Have you noticed whether you have been losing potable water on your cruise and/or your freshwater pump has been running frequently? It could be continually refilling the hot water tank as it leaks.

Ron Hill · August 04, 2025, 02:29:05 PM

Juna : I looked at the video and I'd say you have a fairly good LEAK. You definitely need a new lip seal to stop the water from bypassing the old seal and coming out the weep hole. I'll guess that in not to distant future that leak will become a STREAM!!!

Like I said, the dripping of SALT water down the front of the engine will eventually rust a hole in the engine oil pan!! Then you have a Real Problem!!!

In my opinion you need to also take some time to CLEAN your engine!!

A few thoughts

KWKloeber · August 04, 2025, 03:35:58 PM

Ok Yep, that is more than a "slight leak" but not enough to keep flooding your bilge, so water from another source seems correct.

Ron is correct that it could become more severe, but it's one of those things -- it might or it might remain the same for a month or more (not that I am suggesting that it be neglected any more than now!)

From the quick, glancing shot of the pump front, it appears it might be a round Sherwood pump cover, but with only 4 holes. Strange. If it is the pump that I believe, it's nearly 40 years young, no longer supported, and no replacement shaft is available. There were six or so different pumps used on the M-25. Do you know the pump model? Post pix of it if you want more info.

The inner (forward) lip seal is shot, and the inner (closest to the engine) may also be leaking. From the peeling paint on the gear cover, it appears as if it's been leaking/neglected for a while. When was its shaft inspected last?

Work a wire like a clothes hanger up into the weep hole (which is located between the two seals) to make sure that it is not obstructed by any gunk. It is critical that it is open/allowed to leak; otherwise, seawater could make its way into the gear cover, oil pan, and well, you know what will occur.

Check your dipstick daily for any sign of water, like emulsified oil sticking to it.

If you're brave, pull out the pump impeller and shaft and see if there's a scored line around it, and slather it up with SuperLube or another waterproof grease to help slow the leak past the inner lip seal.

Not to cause unnecessary alarm, the Sherwood CAN seize, and if it does, it CAN snap off the end of the engine camshaft. The good news is I believe yours is a bronze pump, so it's low risk of a sieze-up. But for insurance, check that the seawater pump turns freely during every start-up. The last person I know whose pump seized replaced it with a 12-volt livewell pump to avoid an engine tear-down after the end of the camshaft snapped off.

If engine hoses have been neglected, do check everything to/from the water heater and heat exchanger for leaks that might be contributing to the bilge pump cycling. My understanding of the 34 layout is that there are not-so-easy-to-see spots where a leak could be originating.

-Ken

Phil Spicer · August 05, 2025, 07:07:24 AM

Could there be a leak or crack in the
bilge hose that would let some bilge water back into the bilge and cause the pump to run? Could you have a leak where the cooling water injects into the exhaust? That would cause the water in the bilge to be steaming. Are your fresh water tanks draining?
Just trying to think of how you can get a large water volume in the bilge.
Keep looking for the cause of water in the bilge and keep an eye on that water pump.

junaido · August 05, 2025, 09:44:35 AM

Thanks for all your input and suggestions. The fresh water pump doesn't cycle on/off at the slip but sometimes after a day of hard sailing it will cycle on and off for a little bit before it stops doing that. For the hot water heater, I don't keep it plugged in to shore power but is there any way to keep it out of the engine cooling circuit when I am motoring for several hours?