Raw water intermittently failing- De-bonded impeller

[Stephen Oliver]

Hi Guys

Had a few runs in the last few days – 1 hour south – no problems – then following day a hours run up the Swan River (Perth) and had an engine overheat alarm go off after about 45 minutes – Port side. I have an issue with this engine running hot anyway but i’m fairly sure its electrical as all gauges are off compared the the SB side. I’ve just got to trace everything through. Anyway this alarm was genuine as I could hear the raw water out the exhaust was at a minimum.. so shut the engine down and though we may have picked something up in the intake. (The Swan river is more jelly fish than water!) so reversed, then carried on for 5 minutes on one engine.. started the port back up and raw water was back to normal.. all good so carried on..

Today after a night on the river we had a 2 hour trip back. All good down the river and all good until 15 minutes from port, same thing.. heard the exhaust burbling and no raw water. Shut it down, ran on one engine and reversed also.. and tried a couple of times to start it.. with no joy. I was fairly happy with that as no water should be an easy find.. as something is blocked solid, impeller has shredded etc.. so just ran back the last few miles on one engine again.

Our pen is fairly tight so needed the port engine to get in (boat is 14.5m long and we have 17m clearance rearwards) started it up.. got in the pen and then noticed raw water was back to normal.. so now troubleshooting becomes hard again.. because its ‘working’

Any suggestions what could cause these type of symptoms?

Aftercoolers are due to be pulled after this season (2 seasons total) for another full bench strip down.

Port motor is running a DJ pump sherwood copy (but apparently much better)

Rydlyme was carried out while aftercoolers were being stripped last time.

HX were removed cleaned and rebuilt.

Fuel Coolers were removed about 10 months ago

Anodes replaced last month

So at a bit of a loss to find something that could cause this intermittently like it has

Not had any issues like this in my 2.5 years of ownership.. so want to get it knocked on the head as we get some crappy weather that blows in really quick.. so small windows of travel – and a shut down engine makes things a lot slower!

Steve

Topic

[Stephen Oliver]

Thanks Simon
.must be because we can’t trust the Cummins mechs here 😁

I considered removing the pump but space restrictions make it a tough job too. Jack engine, remove engine mount bracket AND engine mount, fight with raw water pipes to get them off then remove the pump, fit the impeller and the fight to put it all back on hoping I hadn’t screwed the alignment up… The pump was new last March and went thru hell trying to get the old one off.. so know the job well 😁 I just thought this time I’d try it the traditional way!

Not a bad thing as the aftercooler comes off so I may as well service it too…

We are based at Hillary’s so don’t get to Swan too often hence me thinking we’d picked up a jellyfish..

Steve

[Simon Jelly]

Hi Steve/Luke,

Seems to be a few of us Perth guys here. What club are you at? I am at Flying squadron.

In regards to your impeller, i always take my whole pump off my port engine and install the impeller on the bench. I find that easier.

Certainly has been a lot of jellyfish around lately…. I managed to get one in the genset sea strainer over xmas…. and the subsequent overheating…

[Mark Tripi]

When I was starting the project to move the r/w pump that question came up from someone. Tony answered that below.

Pump Speed

Just an FYI.. The gear driven pumps on all of the mid-range Cummins Marine engines turn at 1:1 or a just tad faster than 1:1..

Tony

1 user thanked author for this post.

Stephen Oliver

[Stephen Oliver]

Hi Mark

I have the flow charts but just not sure of the ratio of pump to engine.. so at 650rpm engine speed what is the pump doing.. if its one to one there is no way my dock water will keep up and not let any seawater in if the seacock is left open.

The other option is to add the flush post pump and flush with engine off. I can drain the mufflers so would hopefully be ok.. as long as I flush slowly and the drain sump can keep up. I guess the main objective is to just get the engine full of as close to fresh water as possible.

Steve

[Mark Tripi]

I did research it for my pumps, not the same pumps that you have. You can probably get the flow charts from SBMAR or the pump manufacturer.

[Stephen Oliver]

Hi Mark

I followed your post originally as you were doing it. Impressive bit of work to say the least! I have the ability to do something like that (I am a mechanical design engineer) but not the time or resources (3 year old, business etc etc) so was hoping for something off the shelf…. but as with everything I hope for a lot of things.. but get nowhere! I’m just surprised an option isnt available like a PTO take off at the timing end. I guess a few hours and a bit of disassembly is better than not doing it at all like the previous owner!

Out of interest in your research did you happen to know the pump rpm to engine RPM ratio? Trying to work out raw water flow at idle (for fresh water flushing purposes)

Steve

[Mark Tripi]

Steve, I had looked into having a billet timing cover made to mount a pump on the front but ran into some problems making sure the drive gear had enough mating surface and was not too close or far for gear contact depth. I also worries about the aluminum getting work fatigued leading to a crack and worse. I did mount my 4 BTA sea water pump in front of the engine, it is in a post here.

1 user thanked author for this post.

Stephen Oliver

[Stephen Oliver]

Ok so new impeller is in (DJ pump spare I had) and new ones arrive on Friday along with a heap of other stuff including aftercooler oring sets.

I have to say that the job is a PIG I can only access the pump from the rear from above so only doable at full stretch when the aftercooler is off and fuel solenoid and bracket is gone. Hopefully the impellers can last a full cycle of aftercooler service (although after 18 months in seawater the port one was very clean as was the HX)

Is there any trick to getting the impellers in? I ended up cable tying the vanes down and cutting the cable ties in stages as it went in. Problem was I could only get it as far as the splines then i couldn’t push it any further (i’m working one handed due to space) I ended up putting a plug in the impeller thread, using a long stainless tube over the plastic plug (plug centred the tube) and then using a piece of wood to lever the tube inwards – which popped the impeller in nicely but seemed like a lot of effort.

I reckon the port impeller change if not doing anything else would take around 2-3 hours now all up, but still not the 15 minutes of the SB engine! – Are there any options for adapting the timing cover to mount the pump at the front and external? I have space… lots of space at the front of the engine.. which is no help trying to get to the back of the pump!

Steve

[Stephen Oliver]

KevinS wrote:

A follow up to the possiblity of the impeller spinning it’s hub for intermittent overheating. This happened to me this past August whenever I would break 2,300 RPM. I usually cruise at 2,264 to 2,284 so when I would on occassion break 2,300 the overheat would occur. I first pulled the cover plate on the sea water pump and only discovered the issue when I proceeded to pull the impeller. When turning the hub to remove the impeller I found the hub moving and the impeller staying in place .. son of a gun, issue found. I replaced the spun Sherwood with my backup SMX Super 26 (QSC engine).

At least that hub has some external ‘splines’ to hold the rubber in place.. and looks like some glue too.. this has nothing! Certainly a crappy impeller.. Great to know that Luke was spot on and everyone was pretty much in agreeance..

I’m still confused as to how water could still pump.. I guess just luck.. as it caught and drove the impeller then stopped and slipped again!

Now the pain of putting the new impeller back in.

Steve

[Stephen Oliver]

Well great timing for a follow up…

I decided to check the impeller first. It’s a horrible job as there just isn’t any access from the top front or rear. I’m working to see if the top access can be made possible but involves cutting floor beams etc.. not a quick job.

So after pulling the fuel solenoid and it’s bracket off the engine and removing the aftercooler I could get the pump rear plate off.. and it was immediately obvious that it had spun. Pulled the hub out then pulled the rubber out. The rubber had split.

I’ll give it the benefit of doubt that maybe I cooked it with a jellyfish blocking the intake but there is no obvious damage. Either way less than 40 hours.. not good.

New DJ going in tomorrow as I have a spare. New Super 27s being ordered shortly. Aftercooler being serviced while it’s out.

Pictures for your viewing pleasure.. sorry there are no in place ones I was pushed for time.

[KevinS]

A follow up to the possiblity of the impeller spinning it’s hub for intermittent overheating. This happened to me this past August whenever I would break 2,300 RPM. I usually cruise at 2,264 to 2,284 so when I would on occassion break 2,300 the overheat would occur. I first pulled the cover plate on the sea water pump and only discovered the issue when I proceeded to pull the impeller. When turning the hub to remove the impeller I found the hub moving and the impeller staying in place .. son of a gun, issue found. I replaced the spun Sherwood with my backup SMX Super 26 (QSC engine).

3 users thanked author for this post.

Stephen Oliver, David Wesner, Rob Schepis

[Rob Schepis]

That’s a great and safe way to use the Rydlyme Steve. I just did the same with Barnacle Buster in a Yanmar 6LP – full circuit flush in place, now all coolers are coming off for bench service: gaskets, paint, psi test, etc.

1 user thanked author for this post.

Stephen Oliver

[Stephen Oliver]

Great thanks I’ll need to get creative as its the port motor and pretty much not visible directly! Cant say i’m looking forward to removing / changing it if I have to as it was a nightmare changing the pump due to seized / wrecked engine mounts etc.. Still the SMX mounts installed now and greased accordingly will be easy to remove if I have to remove the pump.. i’m trying to avoid that.

I’ll let you know what I find!

Steve

[Tony Athens]

Totally understand the cost thing..

Our impeller interchanges with the Sherwood 27000.

De-bonding– Pull the fuel solenoid plug– Remove the back plate of the pump and crank the engine/watch the impeller. Leave it dry (no lube or water so it’s hard to spin)

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Stephen Oliver

[Stephen Oliver]

Thanks Tony

Goes without saying (having been an avid reader on here for a number of years) that if the impeller has shredded, then another full cooling system strip down will occur.

Re Rydlyme – I use this as a pre aftercooler removal tool – pump it around for 4ish hours before removing the aftercooler and then flush. Remove aftercooler then I only have fin cleaning to worry about. The only way I learned to do an after cooler service is on here – no short cuts – full bench service. It really does not take that long apart from the pressure tests which I leave for 24 hours.

Re the DJ pump ‘pump’ I believe its almost the same as the SMX one certainly better than the Sherwood (not that that is much of an achievement). They were available from NZ at a good price to me. I would have gone SMX pumps, however US – AUD exchange and shipping is a killer at the moment, not to mention Tax at source now that the Aus government has introduced. My freight forwarder now collects it if the retailer doesnt so no escape and another 10% on top. Works out to roughly 160% the cost for the SMX – hence my decision..

As a few people have mentioned the Impeller bushing debonding – does the super 27 impeller fit the DJ pumps. I have some stuff to order from you, so could add a couple of these too. Its a DJ 08-35-1201 which I believe is the replacement for the sherwood 27000k impeller.

Any sure fire way of testing for debonding other than holding the bush and turning the impeller?

Steve

[Tony Athens]

If you are missing any pieces of the impeller, you must find them.

1– inside the aftercooler–On the bench, core out, for a proper service.. Rydlyme will not deal with rubber chunks

2–Inlet side of gear cooler

3– sometimes a few in the heat-X, but not usual as the aftercooler & gear cooler act as “traps”.

4– stuck inside the inlet side of the pump–This happen when the engine shuts down

DJ pump ?? Very questionable overall quality, especially their impellers due to de-bonding issues.

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Stephen Oliver

[Stephen Oliver]

Hi Rob

Thanks for the input. I opened the strainer which was clear. The thru hull I can’t imagine how it could get blocked intermittently.. the first overheat on the river I just put down to jellyfish… But the returning home overheat (sorry forgot to be specific) was ocean on which I have never had a blockage.. if it was the case I’d be buying a lotto ticket tho! Pipe from strainer to pump was new last March.

I’ll be diving the hull to check it out though. Shouldn’t be growth as it was only out in October for antifouling and I stripped the hull strainer back to metal, primed and antifouled individually..

Steve

[Rob Schepis]

Don’t forget to investigate ahead of the pump too – the hull intake and intake hoses.

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Stephen Oliver

[Stephen Oliver]

Hi Luke

Yep good thought – port engine so pain in the rear to get to.. either way i’m going to end up pulling the pump or impeller.. it was only installed 29/3/19 and has done about 35 hours..

I was also wondering if some crud could have got in and was blocking the aftercooler.. but on shut down it dropped back out.. i think this was a bit far fetched tho.

Steve

[Luke Nelson]

Hi Steve,
I would take guess at the bronze bushing slipping on the neoprene impeller at higher rpm? Drop a spare in and see? Worse case is it can be ticked off the list?

Luke

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Stephen Oliver

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