Wet exhaust isn’t wet

[peaman]

A couple days ago I had a fuel pump failure which has been resolved. I replaced the pump and am again able to start the engine. But I seem to have another problem now.

In the course of troubleshooting the fuel problem, I cranked the engine quite a bit in an unsuccessful effort to purge air. I have since recalled that cranking excessively without ignition can lead to a flooded muffler and engine. Having since started the engine, there is no indication that the engine has been harmed in any way, but when I run it, I’m not getting water ejected in the exhaust.

Until I saw this issue, I had not done anything, other than cranking the engine, to affect the raw water circuit. Since it has come up, I have checked the raw water pump (okay), and the seacock and strainer (okay). After running the engine for a minute or so, the raw water pump feels cool, and exhaust components (elbow, hoses, muffler) feel only slightly warm.

I don’t know how long is too long to run the engine while waiting for water to spit from the exhaust. What’s the best course here? What to check? Again, the engine now starts fine and runs normally, but the exhaust is dry. Do I simply need to run it longer? How long?

 

[Prairie Schooner]

We had the rubber of the impeller separate from the metal hub. When I took the plate off, it looked fine. It was only when I took the impeller off that I discovered what was wrong. I don't know if this will be of any help.

 

[peaman]

I recommend @Prairie Schooner for the Lifesaver Award for October. It appears that my impeller had slipped from its sleeve at some point. But as an engineer, I am very sceptical of the incidence of multiple unrelated failures, so I’m curious as to how and when the impeller might have failed. As I noted, earlier, the pump cover felt cool to touch. Later, I removed the cover to make sure the impeller had not lost vanes, saw that it had not, and reinstalled the cover. After that, it did not feel cool again until I replaced the impeller and smoothed the cover using 400 grit wet sandpaper. When I check it earlier, I had noted that the cover had some rough spots, but I figured I could address that later, and I reinstalled the cover with no other steps. With the new impeller, I lubed everything with Dawn dish soap.

Bottom line, things appear in order again, mechanically while my salon is decorated with cushions, tools and supplies everywhere. It’s great to have EY.o as a resource.

 

[Christian Williams]

We have had several similar reports of defective new impellers in which the rubber separates from the armature. Theory is there was a bad batch. I couldn't find the brand reference.

 

[Prairie Schooner]

Our impeller failure was the result of some dumb, absent minded mistakes. We were prepping for a multi-day cruise, rushing to do a lot. I cleaned out the raw water filter but forgot to re-open the seacock. We got about 20-30 minutes into our cruise (no wind) and noticed steam coming out of the lazarette. We immediately shut it down, cleared out the locker and opened the saloon engine panel for it to cool. Running dry for that long no doubt stressed the two year old impeller enough for the rubber to separate from the hub.
Stupid mistakes:
1. Not having a spare impeller
2. Forgetting to open the seacock.
3. Not checking for water flow when we started the engine.
4. Not having an engine temp alarm.

Reading about everyone else's adventures here allows me to think through potential scenarios. That virtual practice definitely helped me implement logical trouble shooting in this instance. We're lucky to live in an area with a lot of supply options. We finally found an impeller in stock about an hour away, got two!!!, installed one, tested it, slept overnight on the boat, and started again the next morning.
As I was troubleshooting, there was still no wind, and none forecast all day, so we ended up with a tow back to our mooring ball. We were really glad to have tow insurance.
I was glad to have a laser temp gun on board.
I'm glad for this forum where I learn so much!

 

[Christian Williams]

Always great to be reminded.

I think it was Ray Durkee, Pete the Cat, who alerted us to a cheap engine overheat alarm that reads from the exhaust manifold. Easy to install.

https://www.amazon.com/Ultimate-Products-Exhaust-Temperature-Alarm/dp/B00PKVF2O8

 

[Prairie Schooner]

Always great to be reminded.

I think it was Ray Durkee, Pete the Cat, who alerted us to a cheap engine overheat alarm that reads from the exhaust manifold. Easy to install.

https://www.amazon.com/Ultimate-Products-Exhaust-Temperature-Alarm/dp/B00PKVF2O8

View attachment 51162

Thanks for the reminder, Christian. I'd forgotten his mention of it. That's going on the winter work list.

 

[Pete the Cat]

We have had several similar reports of defective new impellers in which the rubber separates from the armature. Theory is there was a bad batch. I couldn't find the brand reference.

Also, I have no proof of this, but it seems like there could be a lot of stress on the impeller when first installed. That is why it is good to use some dish soap (don't use a lot of waterproof grease--I learned from experience) to lube it and it is a good idea to sand the face plate. I am conjecturing that those first minutes running dry and trying to draw water through that tiny 3/8" hole (yes that is what it is ID on a M202 Oberdorfer 15) could be a stress on the hub. Just a theory. The pump actually puts an enormous volume through some very tiny clearances and this has to produce a lot of pressure (+ and -) in the system. Once the system is full of water, it has lubrication and cooling.