Raw Water Impeller, Remove or Not

[vyv_cox]

Blimey, just goes to show how big the Bukh is as there's enough room for a life raft in there too!
Regarding a previous question about the pss shaft seal vyv, where have you routed your vent tube?

The two pieces of aluminium angle in the photo support a tool box that I made to fit the space vacated by the Bukh cylinder head. It holds all my spare filters and impellers, a hacksaw, a vice, a selection of files and several other tools. Changing to the Yanmar also saved nearly 100 kg!

The PSS vent tube is the clear reinforced one to the right. It stops just out of the photo.

 

[RichardS]

The two pieces of aluminium angle in the photo support a tool box that I made to fit the space vacated by the Bukh cylinder head. It holds all my spare filters and impellers, a hacksaw, a vice, a selection of files and several other tools. Changing to the Yanmar also saved nearly 100 kg!

The PSS vent tube is the clear reinforced one to the right. It stops just out of the photo.

Your engine looks similar to my 3YM30s Vyv, although the sea water pump is hidden rather than at the front, but is there a good reason, other than for easy access, why you've removed the plastic covers on the drive belt and alternator pulley?

I removed the cover on the top of the alternator pulley on mine as I hope it might improve alternator cooling but perhaps I should go the whole hog and uncover the alternator completely?

Richard

 

[cryan]

So, are you opposed to preventative maintenance?

That is like asking if I prefer sunlight or darkness, sometimes I like it sunny, sometimes I prefer to be in darkness. Some preventative maintenance is good, some does more damage than good. Any engineer who has spent any time in an operational role will tell you that there are a lot of jobs which are seemingly done only to say they have been done and serve no, "maintenance," benefit at all. In the case of jasbco type rubber impellers you will do far more damage to the part by removing it and then trying to squish all the blades back into the casing than would have happened in several hundred hours of running. There is no need to do this as by removing the cover and looking with a torch you can see if blades are splitting at their roots, you can push a thumbnail into the side to see if still soft and you can see if there is any damage or marks. Then you can refit the cover without ever having to stress the blade roots out via disturbance. Good engineering is as much about knowing when not to touch something as when to, "Fix," it.
However in reference to the OPs post in a career at sea and ashore where I must have worked on machinery that was fitted with hundreds of these type of pumps I have never known of one to fail, or be damaged by either sitting idle in anti freeze for six months or by sitting in salt air in a dry casing for a length of time. The materials chosen for manufacture are chosen to deal with these situations.

 

[NormanS]

That is like asking if I prefer sunlight or darkness, sometimes I like it sunny, sometimes I prefer to be in darkness. Some preventative maintenance is good, some does more damage than good. Any engineer who has spent any time in an operational role will tell you that there are a lot of jobs which are seemingly done only to say they have been done and serve no, "maintenance," benefit at all. In the case of jasbco type rubber impellers you will do far more damage to the part by removing it and then trying to squish all the blades back into the casing than would have happened in several hundred hours of running. There is no need to do this as by removing the cover and looking with a torch you can see if blades are splitting at their roots, you can push a thumbnail into the side to see if still soft and you can see if there is any damage or marks. Then you can refit the cover without ever having to stress the blade roots out via disturbance. Good engineering is as much about knowing when not to touch something as when to, "Fix," it.
However in reference to the OPs post in a career at sea and ashore where I must have worked on machinery that was fitted with hundreds of these type of pumps I have never known of one to fail, or be damaged by either sitting idle in anti freeze for six months or by sitting in salt air in a dry casing for a length of time. The materials chosen for manufacture are chosen to deal with these situations.

You are responding to a retired mechanical /marine engineer, who wonders why your method of removing or replacing a Jabsco type impeller, would damage it. I suspect that your method may be suspect. I would defy you to do a proper inspection of an impeller, in situ.

 

[KAM]

I take mine out because the pump cover corrodes if the impeller sits in the same position all winter. 600 hours on the same impeller.

 

[CAPTAIN FANTASTIC]

I leave mime in because "modern" plastics do not suffer with distortion problems to the extend that will cause problems with performance

 

[vyv_cox]

Your engine looks similar to my 3YM30s Vyv, although the sea water pump is hidden rather than at the front, but is there a good reason, other than for easy access, why you've removed the plastic covers on the drive belt and alternator pulley?

I removed the cover on the top of the alternator pulley on mine as I hope it might improve alternator cooling but perhaps I should go the whole hog and uncover the alternator completely?

Richard

It's a 3GM30F that has never had plastic covers and none shown in the manual. It was clear that California-led safety overkill was taking over when I bought my engine, judging by the folder full of stickers that I was supposed to attach to every available surface Presumably they have gone several steps further with the introduction of the YM series.

 

[pvb]

I've always left the impeller in, and never had a problem. I'd agree with Vyv Cox's assessment that vane distortion is another boating myth.

 

[cryan]

You are responding to a retired mechanical /marine engineer, who wonders why your method of removing or replacing a Jabsco type impeller, would damage it. I suspect that your method may be suspect. I would defy you to do a proper inspection of an impeller, in situ.

I do not damage impellers, I have witnessed others who have. We are not talking about licenced Marine Engineers with Tickets from the MCA ensuring their competence in such matters has been examined and assesed - such as myself. We are talking about Joe Blogs practical boater.
Perhaps a quick check of material softness and a visual of fin security is not what an engineer as esteemed as your good self would consider a thorough investigative inspection but for Mr J Blogs' needs I'm sure they will be just fine, especially considering the improved durability of modern materials. I mean, if we are to go to the bother of removing said impeller and carrying out a detailed microscope inspection of the micro cracks caused by material stresses at the fin roots one must wonder why we wouldn't just replace the relatively cheap and disposable part altogether?
Now I know in the good old days when when men were men and steam was King that to keep everyone in a job certain parts of machines were stripped down, checked and rebuilt just because it was a Tuesday and that's what you did on a Tuesday but today we like to take a more liberal approach to operating machinery. Now a days Engineers are expected to question the logic of Tuesday's maintanece for Tuesday's sake and use their knowledge, training, experience and judgement to asses what needs done on an ever evolving and dynamic basis. In today's world if you pull off the cover, feel it's soft and either with your eye, a mirror or one of the many inspection camera devices available, confirm that all fins are present and correct and not torn away from the root then we assume, "She'll be reet." Replace the cover and carry on.


Ps. As you should be aware we Marine Engineers get a wee bit tetchy when annonymous bloggers question our competence without any knowledge of our work. Now if you don't mind Lidl are selling Stolen and this car park is getting cold so I'm going in to the shop.

 

[pvb]

Ps. As you should be aware we Marine Engineers get a wee bit tetchy when annonymous bloggers question our competence without any knowledge of our work. Now if you don't mind Lidl are selling Stolen and this car park is getting cold so I'm going in to the shop.

If you pay for it, it won't be Stolen...

 

[robertj]

The two pieces of aluminium angle in the photo support a tool box that I made to fit the space vacated by the Bukh cylinder head. It holds all my spare filters and impellers, a hacksaw, a vice, a selection of files and several other tools. Changing to the Yanmar also saved nearly 100 kg!

The PSS vent tube is the clear reinforced one to the right. It stops just out of the photo.

so it terminates below the engine box lid, is it just an open end vyv?

 

[cryan]

If you pay for it, it won't be Stolen...

Touché

 

[vyv_cox]

so it terminates below the engine box lid, is it just an open end vyv?

Yes. As per the instructions, just make sure it is above the water line under any circumstances. If the sea level was there we would be concerned about other things!