Seawater not pumping through engine

[Kevin A Wright]

It sounds like you've covered the likely suspects on the inlet side barring something like a jellyfish flapper valve. But rather than start at the discharge of the pump, I'd disconnect the water to the exhaust mixer and check there. That is an area where carbon/Salt/Crud can build up and block the water flow. Often lost of salt buildup due to the hot fitting. If it can't get out, it won't suck in.
If you get water flowing there you automatically know your pump, heat, exchanger, etc is OK and you just need to ream out the injector. If not you can start working backwards from there as next most likely area is heat exchanger,

Good Luck!

Kevin Wright
E35 Hydro Therapy

 

[NickSal]

Just went through the same issue.
M 40 with oberdorfer n202m pump.
No water through the engine.
1. Changed impeller. Some improvement at 2000 rpms or higher no water
2.remove and clean heat exchanger. No help
3. Oberdorfer Repair kit for the pump, pressed new carbon bearing and seals. Nothing
4.got a new pump at $270, installed. Problem solved, a lot more water going through the engine.

The issue was progressing since I got the boat 4 years ago. I guess Water pump is a consumable that need to be replaced outright at some point.

 

[dcoyle]

You are getting lots of advice on this issue, at the risk of overwhelming you with info I wanted to add a relevant suggestion. I had a similar problem a few years back, water fed to pump but not out of pump. Fix was blocked air vent, cleaned out vent and system worked again.
There is a zinc on your heat exchanger which can be removed and raw water should flow out. That can be used to trouble shoot.

 

[Second Star]

Not sure which pump you have, but you do mention an O ring to seal the face of it? On mine the seal is a very thin paper gasket, If there is a gap between the face and the impeller the pump will not work. Even if a groove is built into the pump or faceplate the wrong size O ring would cause problems.

 

[lindaloo]

I had a similar problem years ago and we changed out every hose but the through-hull to pump inlet. I finally did and that was the problem all along. The hose inner lining had partially detached and was acting like a check valve. We too had run water OUT with a garden hose. The inlet hoses are suction and thus may (should) have spiral wire. Pressure side can be fabric reinforced.

Set up a full 5 gal pail and a short hose to the pump INLET.

Rob

 

[K2MSmith]

Progress.

Everybody is now thinking the same thing: something clogging the run of hoses and heat exchanger. Test them one by one.

I recently changed all the hoses on my cooling system, and here's what I learned:

--For access, remove stuff in the way. In my case, the waterlift muffler and its big exhaust hose. If necessary, the water heater, too. Its an hour's work, and that's the first thing a boatyard does at $130/hour.

--Specialty tools really help for this work, notably a small socket wrench to fit the many hose clamps (forget a screwdriver in confined spaces). Some old hoses are fused to their barbs or stubs. For that, a 10-dollar “Drake Off Road 4521 Hose Removal Tool” is a luxury. A heat gun is required too, along with towels for spillage for the inevitable mess of drained fluid, raw water and knuckle blood.

--I'd probably start by taking out the heat exchanger. It should come out anyhow, so you can properly clean it of scale. And it may well be the problem.

Here's more on my experience, with links to Hx boil-out in the Comments section.

Marine Diesel Cooling System Upgrade 2020

Symptoms: Apparent decrease in water volume at exhaust. Temperature RPM limitation at Wide Open Throttle. Steam from exhaust at idle. Solution: clean heat exchanger, optional general upgrade. [Note 2024: For routine maintenance of the cooling system I later had success with the immersion...

ericsonyachts.org

More progress … binary search . I disconnected the seawater output of the heat exchanger and fed it into a bucket and started up the motor . There is plenty of water flowing through that part of the system. Filled a bucket in about 30 seconds . So must be a clog *after* the heat exchanger. Meanwhile, can someone help me identify this part ? Is this the unit that mixes with exhaust? Also see heat exchanger photo . A slip neighbor tells me he helped the PO replace it ( and all the hoses ) 3-4 years ago . So it’s not that old .

 

[cruis-n]

More progress … binary search . I disconnected the seawater output of the heat exchanger and fed it into a bucket and started up the motor . There is plenty of water flowing through that part of the system. Filled a bucket in about 30 seconds . So must be a clog *after* the heat exchanger. Meanwhile, can someone help me identify this part ? Is this the unit that mixes with exhaust? Also see heat exchanger photo . A slip neighbor tells me he helped the PO replace it ( and all the hoses ) 3-4 years ago . So it’s not that old .

I had a similar issue and traced it to the elbow that injected the output of the heat exchanger into the exhaust riser.
https://ericsonyachts.org/ie/threads/m-25-exhaust-riser-choice-of-metals.14835/#post-108565 port #16

Good luck.

Paul

 

[Christian Williams]

Exhaust elbow. Looks like it has fitting for HX water injection, top left. Good place to examine next, as others have reported clogs there, and you have a 90-degree turn. The exhaust riser/elbow gets hot, sat water is injected, scale gets formed.

The solution to this one will be interesting and informative. And you'll get there.....

[posted simultaneously]

 

[K2MSmith]

Not sure which pump you have, but you do mention an O ring to seal the face of it? On mine the seal is a very thin paper gasket, If there is a gap between the face and the impeller the pump will not work. Even if a groove is built into the pump or faceplate the wrong size O

Exhaust elbow. Looks like it has fitting for HX water injection, top left. Good place to examine next, as others have reported clogs there, and you have a 90-degree turn. The exhaust riser/elbow gets hot, sat water is injected, scale gets formed.

The solution to this one will be interesting and informative. And you'll get there.....

[posted simultaneously]

There is a short length of hose that runs to this elbow . When I “blow” into this hose , there is no air getting through so it appears either the hose or the actual elbow is blocked . So , I’ll have to take this apart next probably from the front of the engine - when I return .
On a separate note , I don’t fully understand the operation of the “exhaust elbow” . There is a separate “wet pump” attached to the exhaust hose ( about 2.5” dia) , but there also appears to be another coolant hose at the base of the exhaust elbow that goes to the coolant tank . Is the idea to “cool” the exhaust with seawater or to just provide one exhaust hose for both exhaust gas and raw seawater ? If the former , then why is coolant running through it also ? Seems like a weird and complicated way to do it , but I guess it has worked for 100 years , so .

re: on the seawater pump . I put a new o ring in the cover groove with silicone paste with new impeller ( also hard to find but a different story ) . As it turns out the pump was working fine ( see earlier in thread ) .

 

[Loren Beach]

Note that on the 80's Universal diesels, they put a 1/4" hose from the top of the water exhaust injection point all the way to the transom. This was a syphon break. Also, this exit did not appear on the transom because they brazed a stub of copper tubing onto the inside of the exhaust fitting to receive that little hose.
For the curious, the Olson's had this little thruhull exit fitting mounted just above the exhaust fitting. Trivia: when we replaced the OEM Universal with a new Betamarine, their instruction said that having this little syphon break was optional, and they did not require it. So I glassed over the former hole in the transom.

 

[K2MSmith]

Note that on the 80' Universal diesels, they put a 1/4" hose from the top of the water exhaust injection point all the way to the transom. This was a syphon break.

I’ll take a Picture but my boat has a 1/4” vent hose at the water / exhaust seacock. The other end is basically just wire tied to a higher point under the cockpit .

 

[Kenneth K]

If your siphon break does not exit at the transom, as Loren described (mine exits at the exhaust through hull), then your blockage likely occurs before this siphon break/ventline. If the blockage was after the siphon break / ventline take-off, it's likely the siphon break/ vent line would be pumping water into your cabin or hull.

 

[K2MSmith]

If your siphon break does not exit at the transom, as Loren described (mine exits at the exhaust through hull), then your blockage likely occurs before this siphon break/ventline. If the blockage was after the siphon break / ventline take-off, it's likely the siphon break/ vent line would be pumping water into your cabin or hull.

Maybe I don’t understand Loren’s description completely. There is a 1/4” vent hose at the large exhaust/seawater output thru-hull. It doesn’t exit the boat . I don’t recall seeing a vent hose at the exhaust manifold/mixer. I’ve attached a photo of the exhaust manifold . I don’t have a pic of the vent hose / thru hull . I suspect block is at the “L” inlet ( or in the hose ) . When I blow air ( from my mouth ) into this hose , it’s completely blocked- no compression- it feels the block is there . I have another trip next week , but I’ll resume looking at this part when I return. I have receipts from PO that show the HX was replaced in 2019. The exhaust manifold / mixer pipe looks pretty new as well . So I doubt there is corrosion or calcification, but who knows . If you zoom in on the photo , it appears that the inlet is threaded and has a square shape to it , so maybe it can be easily removed with a crescent wrench . Unfortunately it’s in a spot that not easy to reach , but I’m getting used to lying down below deck

 

[Kenneth K]

Here is the usual setup (pic stolen from goldenstate):


The left hose comes from the heat exchanger. The right goes to the injection elbow. Between the 2 larger hoses is a T-fitting from which the smaller anti-siphon vent hose originates.

 

[bigd14]

To add to Ken's photo above, here is a photo of the exhaust system I installed. In the second photo you can see the siphon break line leading off the raw water line between the (remotely mounted) heat exchanger and the mixing elbow. The original part was a copper tube soldered to a straight pipe nipple. I just cobbled it together with a tee and reducer, two elbows and hose barbs in stainless steel. It exits through a dedicated thru hull on the transom. Under normal operation the amount of water this pees depends on engine speed just like the exhaust output. I agree that raw water elbow on the mixing elbow is a suspect area. Good luck, you're getting there.

 

[Christian Williams]

I suspect block is at the “L” inlet ( or in the hose ) . When I blow air ( from my mouth ) into this hose , it’s completely blocked

That hose, from hx to elbow, is the only source of water coming out the exhaust. So if it's blocked....

 

[CTOlsen]

I had a similar, although less significant problem a short while ago; low water flow through the engine leading to vaporizing of raw water out the transom discharge. I disconnected hoses and inspected parts to discover that the problem was on the inlet side. I found that the strainer cover was cracked, allowing air leakage into the suction, reducing water flow. I replaced the cover, added new O-Ring, and nylon washer at the strainer cover bolt and the problem was solved. Good luck- there is a solution.

 

[K2MSmith]

To be continued… I’m in SoCal for the next week so will resume working on this when I return. (one benefit of not teaching in the summer is I can do this stuff during the week until August). It is pretty clear that the problem is in the hose to the exhaust elbow or the exhaust elbow itself (inlet or the pipe). If it is the exhaust elbow, the diesel mechanic suggests I remove it and replace it. Further reading indicates they are are a regular maintenance item that can be clogged, calcified or carbonized - reducing engine performance. Since I’m already there, might as well.

 

[K2MSmith]

I was able resume working on this problem. I managed to take the seawater inlet off of the exhaust elbow with crescent wrench . It was blocked with gunk . Even after I clear it, it seems restrictive when I blow through it . Maybe just easier to order a new one if I can find it . Anyone know what this is called and where I can get one ? Also there didn’t appear to be any o-ring or washer to seal the threads. I’m wondering if I need to install a sealer or tape when I reinstall it, although the exhaust elbow can get really hot . Looks like it is made of brass.

 

[Christian Williams]

Can it be a straight fitting, like mine? A 90-degree turn might not be necessary if the hose permits.

Brass not recommended for seawater, mine looks like bronze.