ALWAYS check your exhaust water!

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boathealer

boathealer

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BOTH engines. Simultaneously. 230hrs. Strange. Haven't figured out the root cause.
 

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Did you check your strainers? You may have gone through some grass, clogging the strainers which made the impellers work much harder.
 
SOP: examine exhaust water-flow upon starting engine(s).
 
I have a Borel alarm system on my exhaust. Very simple uses no power until it has an alarm condition. Mine also monitors water in fuel and high water alarms.
 
Have Borel alarms. Observed lack of flow before alarms were an issue.

1 year old. 230hrs.

Happened immediately on splashing after only 6 hours in the yard. All fine prior. All in a clear harbor. Thru-hulls closed just prior to going into slings, reopened as soon as splashed.

Water not present at exhaust right at startup.

Very strange to me.......
 
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Could it be an air lock from the through hull to the engine meaning they were running dry?

Or,

Did they paint over the pick ups? (If you got a bottom job).
 
menzies said:
Could it be an air lock from the through hull to the engine meaning they were running dry?

Or,

Did they paint over the pick ups? (If you got a bottom job).
Click to expand...

Certainly could be, however they were closed prior to haul and reopened upon splash. If drained somehow (drripless seals?) should only have been dry for 20sec or so as hose is only 4ft from thru-hull to pump?

No bottom paint involved. Clear strainer(s) ther whole time.

Stymied.☹
 
That is always the first thing I do right after firing up the engine. I go aft and check water flow, also check water flow in strainer. Few minutes after I go on the swim platform and check with my hand that water is warm not hot as too hot means not enough flow.

L
 
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.
 
I always check for water from both engines right after start before doing anything else. Although with the big water lift mufflers on my engines it's also very obvious by sound if there's not enough water to keep the mufflers filled.
 
Ditto on always checking exhaust flow after starting (and periodic checks while underway as well). As SOP it helped me to identify that my stbd transmission cooler had failed, as all of a sudden I had a bit of a slick in the exhaust flow wake... So there's multiple reasons to always check!
 
What is funny is that, by experience, unfortunately I should say, I discovered that it is easy to find out there is no water going out of exhaust just by the sound of it. It occured once for me underway and suddenly my boat was roaring like a big truck instead of purring like an happy cat.

L
 
Lou_tribal said:
What is funny is that, by experience, unfortunately I should say, I discovered that it is easy to find out there is no water going out of exhaust just by the sound of it. It occurred once for me underway and suddenly my boat was roaring like a big truck instead of purring like an happy cat.

L
Click to expand...
Heard of that but never experienced it. Personally, I check my exhaust water every morning just after rising, can`t be too careful :D.
Your hint to recheck exhaust water heat after a few minutes is a good one, so far I`ve trusted my gauges.
 
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That is definitely a sign of heat or cavitation. It might have been caused by a vacuum leak of the sea strainer caps.
 
On my boat at least, easy to shoot the temp of the exhaust hose downstream of elbow on ER checks
 
On my single F.L. I ALWAYS check for water output. Even though I can hear the back flow clattering and can hear the occasional big splash out the back when the muffler fills and empties.

Not so much with diesels but with gassers you could tell by the sound the instant the exhaust became "wet". Still miss that "contented gurgling"

pete
 
Does your boat have a seawater chest instead of seacocks for the water intakes? If so, would you have to purge air from the chest after splashing so water could reach the hoses?

I've seen photos of N47's that have them, so thought yours might as well.
 
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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.
 
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.
 
Were perchance the engines turned over or attempted to be started while on land?
 
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.
 
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.

20181111_052501.jpg

20181111_052535.jpg

Ted
 
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.
 
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!
 
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.
 
Dcbeach said:
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.
Click to expand...

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.
 
O C Diver said:
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
Click to expand...

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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