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Old 02-14-2020, 01:35 AM   #21
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If only one impeller came apart I would think you sucked a bag or some other debris that floated off after you stopped your engine. Both of them going off at the same time suggests that the engines were run with the valves closed but possible you sucked debris in both engines that floated away after stopping.

I’ve seen impellers nearly that far gone still pumping water.
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Old 02-14-2020, 03:08 AM   #22
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Looking at the witness marks on the end plates it seems that there is minimal space between the cam and impeller boss, I suspect that it wouldn’t take to many seconds of no or low water flow to make some decent impeller damaging heat.
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Old 02-14-2020, 04:00 AM   #23
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Were perchance the engines turned over or attempted to be started while on land?
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Old 02-14-2020, 06:43 AM   #24
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Boathealer: Were you on the boat when splashed and did you start up the engines? Or did the yard guys do the start-up?

Sure looks like someone goofed and started engines with the cocks closed.

Sometimes after a haul a worn pump won't pull a prime. But pretty rare on main engines, common on gennies.
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Old 02-14-2020, 08:51 AM   #25
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What make of impellers (not make of pump)? Maybe a bad batch.

The other consideration is that some engine configurations require limited liftt capacity as everything is below sea level until the exhaust goes into the exhaust lift muffler. As a result, you may have already lost a number of blades on each impeller before they finally quit. This would happen on my Onan generator. I can loose 9 of 12 blades on the impeller before engine temps start to rise. My solution was to add a strainer after the pump to catch the blades (as opposed to them going in the heat exchanger). Simply check the strainer every time when you check the oil.

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Old 02-14-2020, 08:53 AM   #26
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Interestingly, on my main engines, I've found that if an impeller fails before I replace it due to age, it's usually when winterizing. It usually happens as sucking a little bit of air while I'm feeding in antifreeze and the worn out impeller loses prime and can't re-prime. Then it's impeller swap time. On the generator, as long as the impeller is changed before the 7 year mark, they seem to just keep going.
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Old 02-14-2020, 08:54 AM   #27
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I closed and then opened the thru-hulls myself. I was with the boat the entire day. Engines were not started on the hard.

Sea chest has large vent hole on top - no worries there.

Sea chest has a fine grate/strainer at hull opening - 3/16" holes.

The scoring on the cover plates might be a good clue though! I have new plates on now with new impellers. I will open and inspect them after a few tens of hours....

Thanks!
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Old 02-14-2020, 08:54 AM   #28
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My Perkins in a 34 Mainship always needed a priming after splash. I needed to close the sea cock. Open the strainer and fill the strainer with water. Simply opening the sea cock was not effective. I’m assuming there was an airlock in the engine hose and by opening the strainer enough air was “burped” out of the engine hose to allow the water pump to pull salt water. In my case it was a 1 1/2” hose about 4’ long.
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Old 02-14-2020, 08:56 AM   #29
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My Perkins in a 34 Mainship always needed a priming after splash. I needed to close the sea cock. Open the strainer and fill the strainer with water. Simply opening the sea cock was not effective. I’m assuming there was an airlock in the engine hose and by opening the strainer enough air was “burped” out of the engine hose to allow the water pump to pull salt water. In my case it was a 1 1/2” hose about 4’ long.
After launch I usually loosen the strainer lid slightly with the seacock open until water overflows out of it. Once that happens, tighten it up, confirm no leaks and then the engine is ready to fire when needed.
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Old 02-14-2020, 09:04 AM   #30
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What make of impellers (not make of pump)? Maybe a bad batch.

The other consideration is that some engine configurations require limited liftt capacity as everything is below sea level until the exhaust goes into the exhaust lift muffler. As a result, you may have already lost a number of blades on each impeller before they finally quit. This would happen on my Onan generator. I can loose 9 of 12 blades on the impeller before engine temps start to rise. My solution was to add a strainer after the pump to catch the blades (as opposed to them going in the heat exchanger). Simply check the strainer every time when you check the oil.

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Thanks, Ted!

Yanni 4JH4E engines. Yanmar impellers. 2017 date stamp on pig. From waterline to pump (lift) is about 1 inch 😉

Good idea on the strainer!
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Old 02-14-2020, 09:47 AM   #31
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My Perkins in a 34 Mainship always needed a priming after splash. I needed to close the sea cock. Open the strainer and fill the strainer with water. Simply opening the sea cock was not effective. I’m assuming there was an airlock in the engine hose and by opening the strainer enough air was “burped” out of the engine hose to allow the water pump to pull salt water. In my case it was a 1 1/2” hose about 4’ long.
I experienced a similar fate on my FL after impeller change. Filling the strainer did not burp the air between strainer and pump. Had to disconnect hose from the strainer and fill it with water.

I caught it within seconds of starting so no damage to the impeller. I grease up the impeller and the inside of the pump when replacing impellers.

I recently started using Globe Run-Dry impellers in the generator. They are guaranteed to run 15 minutes without water. As soon as I use up my stock of engine impellers, I will switch to Globe.

I replace impellers every two years.
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Old 02-14-2020, 11:06 AM   #32
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Sure looks like someone goofed and started engines with the cocks closed
The fact that this happened with both engines supports the "both cocks closed" theory. Whether the yard started the engines without opening the sea cocks is debatable but the result accurately describes the position of the sea cocks at the time of engine starting.
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Old 02-14-2020, 12:51 PM   #33
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I agree with Codger. I have CAT 3208 T/As. I change the impellers every year before heading north. Cost of new Impellers is cheap. I save the old ones for spares. Cheap insurance.
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Old 02-14-2020, 01:41 PM   #34
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Some engines don't prime well on start, especially after a haulout where pumps and plumbing might drain down. Worse with old high hour pumps where impeller chamber has wear. Worse also on pumps that are mounted higher up, and ones driven by cams which run at half crank speed.

If you can't see the exhaust easily after a start, go in engine room and put your hand on the back of the pump. If cover plate is getting warm, it is not pumping.
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Old 02-14-2020, 03:28 PM   #35
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How is it fixed to whatever it is measuring?

And is the alarm remote or on the unit itself?
Probe attached with electrical tie
Alarm is piezo buzzer bought separately and wired in

Main engine has one of these for $100
https://engineguard.com.au/
Does the same just costs more.
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Old 02-15-2020, 08:08 AM   #36
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I experienced a similar fate on my FL after impeller change. Filling the strainer did not burp the air between strainer and pump. Had to disconnect hose from the strainer and fill it with water.

I caught it within seconds of starting so no damage to the impeller. I grease up the impeller and the inside of the pump when replacing impellers.

I recently started using Globe Run-Dry impellers in the generator. They are guaranteed to run 15 minutes without water. As soon as I use up my stock of engine impellers, I will switch to Globe.

I replace impellers every two years.
I recall (somewhere back in my decrepit brain) some negative comments about those Globe run-dry impellers. Anyone here running them in main engines? Any real-world data to share?
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Old 02-15-2020, 08:26 AM   #37
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The Globe impellers have been around for a long time, but in my 25yrs of engine business, I have never dealt with them on a customer's boat. Just no experience to report.

Most rubber impeller pumps are super reliable, only three come to mind as troublesome: Cummins Sherwood 1700 series (like on my 450C), those things tend to shed vanes in under 500hrs. And the pumps leak (early versions, but that is another topic). Some Onan gennies where pump runs 900rpm, they don't like to prime every start. And some Volvo 4X series where pump is mounted up high driven by inj pump at half speed, they often don't like to prime.

I've seen many Detroit Diesels with Jabsco pumps where the impellers were at least ten years in service. Scold the owner that they should be changed way before then. Pull the impeller and it is fine!! Maybe vanes bent over a bit with some wear, but all vanes still there.

Wish Cummins had used Jabsco!!
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Old 02-15-2020, 08:54 AM   #38
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There was a stretch of time when the Globes developed a high failure rate as reported on the intetnet....who knows how accurate it was.

Alarming enough for many to stop using them..

Haven't heard/read anything lately....maybe better or just less users to report?
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Old 02-15-2020, 09:44 AM   #39
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There was a stretch of time when the Globes developed a high failure rate as reported on the intetnet....who knows how accurate it was.

Alarming enough for many to stop using them..

Haven't heard/read anything lately....maybe better or just less users to report?
I heard the same things, but have used the Globe impellers on some outboards without issue.

Ken
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Old 02-15-2020, 09:56 AM   #40
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I've had the Globe on the generator for less than a year. Will see how it looks at the end of two years.

If good, I'll try it on the FL.
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