ALWAYS check your exhaust water!

[syjos]

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.

 

[Codger2]

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.

 

[Alaskan Sea-Duction]

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.

 

[Ski in NC]

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.

 

[Simi 60]

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.

 

[boathealer]

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?

 

[Ski in NC]

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!!

 

[psneeld]

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?

 

[kchace]

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

 

[syjos]

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.

 

[Lou_tribal]

It would be great to have the impeller housing transparent so to check the impeller without having to unmount everything.

L

 

[boathealer]

It would be great to have the impeller housing transparent so to check the impeller without having to unmount everything.

L

What a brilliant idea! Is there any kind of acrylic/glass or something that could stand up to that?

 

[Aquabelle]

Sure makes my Borel alarms, which have no temp display, look like expensive dinosaurs! I see they even have dual probes and displays in a single unit (think twin engines)

This on the exhaust elbow has saved us more than once.
As soon as there is restricted water flow, temp goes up, alarm makes noise.
$12 well spent.

https://www.trawlerforum.com/forums/s6/cheap-engine-temp-alarm-38822.html

 

[Aquabelle]

That's a very good genset tip....thanks

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.

View attachment 99367

View attachment 99368

Ted

 

[firehoser75]

Boathealer,
I am not familiar with the "sea chest" instead of a sea strainer? However, it sounds like both engines are fed their cooling water from the same sea chest? At least, they both suffered a lack of supply at the same time. I have heard of this happening when the thru hull is left open when the boat is lifted, but this is not the case for you.

I know that on a former boat, I suffered a lack of supply when the lid on my strainer was not secured tight enough and was allowing an air leak, therefore the pump would not prime properly. Could something along those lines have occurred?

To hopefully avoid issues like this, I installed an Aqualarm water flow alarm that is located between my sea strainer and the raw water pump. As long as the alarm is functioning properly, it (is very loud) will sound an audible alarm and light a red light (located by my helm station) to warn of a poor or lack of water flow. For one engine the whole "set up" cost about $150 for parts.
Other advice like checking the pump for heat right after startup are good ideas, but require you to enter the ER.
Hopefully you will determine the cause of this, to avoid a repeat.

 

[rgano]

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.



Ted

This kind of idea is the nugget I am always looking for when trudging through forum threads! Thanks, Ted.

 

[rgano]

I heard the same things, but have used the Globe impellers on some outboards without issue.

Ken

Went through a few of them in SHORT order on my Onan in the early 1990s. Quit them.

 

[boathealer]

Boathealer,
I am not familiar with the "sea chest" instead of a sea strainer? However, it sounds like both engines are fed their cooling water from the same sea chest? At least, they both suffered a lack of supply at the same time. I have heard of this happening when the thru hull is left open when the boat is lifted, but this is not the case for you.

I know that on a former boat, I suffered a lack of supply when the lid on my strainer was not secured tight enough and was allowing an air leak, therefore the pump would not prime properly. Could something along those lines have occurred?

To hopefully avoid issues like this, I installed an Aqualarm water flow alarm that is located between my sea strainer and the raw water pump. As long as the alarm is functioning properly, it (is very loud) will sound an audible alarm and light a red light (located by my helm station) to warn of a poor or lack of water flow. For one engine the whole "set up" cost about $150 for parts.
Other advice like checking the pump for heat right after startup are good ideas, but require you to enter the ER.
Hopefully you will determine the cause of this, to avoid a repeat.

Photos of sea chest and bottom strainer/grate(s). Sea chest really isn't horizontal - just can't get that one to rotate correctly

The sea chest has every thru-hull on my boat going to it. There is an air vent/escape at the top, so no air lock possible.

I have made removable strainer grates for cleaning/maintenance.

I have Borel alarms on the exhaust, but IMHO by the time they go off, it is sort of too late. I think your earlier indication from the Aqualarm is a good idea.

I am fairly convinced now that in my case some damage must have occurred in the 230hrs/1400 miles prior (sand, air, etc.) and that the incident this time (probably just the 15-20 sec dry run for re-start) was just the "last straw" and quite nicely finished off the impellers.

Thanks for an informative discussion!

Best,
Ray

 

[oscar]

It would be great to have the impeller housing transparent so to check the impeller without having to unmount everything.

L

Here's one for a Bobo..... suspect you may find other ones for other makes....

https://www.ebay.com/itm/Volvo-Pent...parent-Sea-water-strainer-cover-/223134977759

 

[Lou_tribal]

Here's one for a Bobo..... suspect you may find other ones for other makes....

https://www.ebay.com/itm/Volvo-Pent...parent-Sea-water-strainer-cover-/223134977759

It was about pump impeller housing, no sea water strainer

L

 

[Ski in NC]

Anything clear as a pump cover plate will get abraded quickly and no longer give a clear view.

 

[oscar]

It was about pump impeller housing, no sea water strainer

L

Oops, my bad. And this is a good point:

Anything clear as a pump cover plate will get abraded quickly and no longer give a clear view.

A thin metal plate on the inside with slots in it could provide a partial view and protect against abrasion. This is something one could experiment with, as it is a simple piece.

 

[Mischief Managed]

Did you use anti-freeze to Winterize? May be a chemical reaction between the anti-freeze and a faulty batch of rubber impellers.

 

[MurrayM]

Could the sea chest air vent have been stuck/obstructed/impeded from allowing water into the sea chest?

 

[Northern Spy]

Oops, my bad. And this is a good point:



A thin metal plate on the inside with slots in it could provide a partial view and protect against abrasion. This is something one could experiment with, as it is a simple piece.

Keep in mind that the impeller vanes seal against the pump body and cover plate axially as well as the pump body radially.

Any axial gap allows the vanes to bypass with decreased pump efficiency.

A thin strip of metal would likely just get "picked up" by the vanes as it passes the created step and destroyed as well.

Interesting idea though.

 

[kapnd]

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.

Cheap insurance for sure, but why not keep a fresh one for the spare?
If I have to change one out, I only want to do it once!

 

[slowgoesit]

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.

Except that the OP stated in post # 27 (quoted below) that the thru-hulls were OPEN)

Quote: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!End Quote

 

[Alisske]

Were perchance the engines turned over or attempted to be started while on land?

Exactly my thought. If they did some service and n the engines or something and just wanted to “make sure it ran” and maybe felt a short run would be OK.

Shame. Sorry to hear.

 

[Gulf Comanche]

Lou I also immediately check exhaust water for a full minute. I through my head over the rail aft and wait till I see a big belch of seawater. My seawater output is never steady.
Don’t check the strainer though.

Same here, seawater flow is never steady, always kind of a belch. Always wondered why.

 

[Lou_tribal]

Same here, seawater flow is never steady, always kind of a belch. Always wondered why.

Because exhaust gas pressure needs to build up before expelling water.

L