yanmar 2cyl genny Impeller Q

[vas]

evening all,

trying to get my mase genny running after the refit and seem to have an odd problem, bear with me.

Yanmar 2S engine, running at 3K rpm or there abouts
Only thing I did over the refit was to remove the impeller housing (cannot change impeller anyway without taking it all out), and since inlet was a measly 18mm dia (or even 16mm) and I had a 21mm internal dia injection, seacock and strainer I removed the inlet off the housing and replaced it with a larger one.

Anyway, engine fires up (after figuring out that in order to prime with the manual lever one has to turn (by hand) the flywheel to get some travel...) BUT no water comes out of the exhaust.
New impeller, clean housing, instant gasket on the cover, screws tightened properly.
Head from sea water level to actual impeller intake is a little over 30cm!
On starting the engine, seawater level rises on the wire reinforced head is reduced, water only needs a further 120mm for the sea water to suck in and do it's job.

Now, removed and refitted the impeller (housing) half a dozen times. Noticed that if I suck or blow on the inlet, air comes straight through which seems odd.
Note of air escaping changes as i manually rotate the pulley of the housing.

Q1. is that right? I'd have thought that impeller in the housing with a properly tightened impeller cover should work!

Q2: is it possible that the "height" of the new impeller is slightly less than the original one and it fails on this sealing?

Any other Qs .

cheers

V.

 

[Mr Googler]

Is the strainer after the impeller. I have often "primed" an impeller by pouring sea water into the strainer when the system has been drained down. it saves the impeller running dry and gets pumping water straight away.

Apologies if I have misunderstood the layout.

 

[vas]

thanks F.,

strainer is a good 2m before the engine over the seacock.
Mind I did try to prime the impeller (although it shouldn't really be necessary!) by removing the hose on the outlet of the housing where it meets the coolant heat exchanger but the water went straight through the impeller and on the inlet side level to the sea (effectively pushing the seawater down)

There's no sealing what so ever happening within the impeller housing!
I'd have thought that impeller housing should be water/air tight.

I mean blowing on the inlet without any effort all air comes out from the outlet. If I block the outlet thing is sealed
I can only assume that the impeller is wrong or housing/cover is badly worn.
Genny has just 1K h on the clock.
Should I just get another impeller housing and be done with?

Going to the shop I bought the impeller to check if there is another identical one with 1 or 2mm longer body (which imho would be daft!) They also keep in stock a series of impeller housings for small fishing boats, I'll do the blowing test on them, pretty sure they'll be sealing and not blowing straight through...

cheers

V.

 

[Portofino]

On my Mase -air cooled -

The water enters via seacock goes to a vetus antisyphon thing mounted 1M above the Geny then
To the radiator ( to cool the air ) -then to the pump ,then exists into exhaust manifold .

From the radiator / heat exchanger to pump is INLET Your 1st paragraph sugests "outlet"

Are you thinking it all the wrong way round ?

Prime the radiator / heat exchanger 1st---- if this is full ish pump will draw ,but check impeller is right way round too ,they can self correct but these are tiny and may rupture if put in wrong way round ?

 

[vas]

On my Mase -air cooled -

The water enters via seacock goes to a vetus antisyphon thing mounted 1M above the Geny then
To the radiator ( to cool the air ) -then to the pump ,then exists into exhaust manifold .

From the radiator / heat exchanger to pump is INLET Your 1st paragraph sugests "outlet"

Are you thinking it all the wrong way round ?

Prime the radiator / heat exchanger 1st---- if this is full ish pump will draw ,but check impeller is right way round too ,they can self correct but these are tiny and may rupture if put in wrong way round ?

nice,

you completely confused me at first.

Bearing in mind that mine is an older I think gen of two cyl yanmar (its a 2S engine) I'm pretty sure that the flow is as I describe. After all, it did work when I got the boat 4yrs ago and was pushing water around...

Water comes in from the left as you see the front of the engine, then to the right is a specially formed hose that goes to the heat exchanger and through it straight in the exhaust elbow for mixing with the gasses.
No doubt about it, especially as water level on the clear ss reinforced inlet hose clearly comes up and almost makes it to the engine when running.

Read a thread on the topic, read a couple of other discussions on the jabsco vs Johnson debate on their pumps and I may have a slightly worn pump struggling to get the suction.

Got the pump to the place I bought the impeller, were confused initially as turning it didn't make the right noises (had smeared liberally the vanes and housing with grease to avoid issues of dry running) declared that this is completely wrong, and even went ahead and took it apart, cleaned everything, replaced with another impeller and sealed it again with instant gasket on the faceplate. IE, did exactly what I'd done bar the grease considering what I'd done wrong, go figure...
They were happy that the noise produced by the thing when turning the pulley is there, but couldn't answer my simple question on WHY when blowing on the inlet (or outlet) the air with minimal (read none whatsoever) restriction comes out from the outlet (or inlet) whereas on all the new pumps they had (ok, slightly larger) inlet was almost sealed from outlet and vice versa.

Left the place wiser only on the obvious fact that this shouldn't happen and with a stronger opinion on the technical capabilities of the staff of that place...

I'm tending to conclude that the casing is worn and the vanes don't seal (top and bottom of the "barrel" they rotate) Cam seems to be fine and proud compared to some worn examples I've seen on the web. Mind you, there was no strainer fitted when I got the boat I fitted a guidi (sp?) one over the new replaced seacock. And before you ask, yes it seals properly no air bubbles anywhere. Wouldn't' be as strainer is around 150mm lower than waterline, may move it up at some point.

Two options:

A. get another pump and be done with, only got to be locally due to these capital control mess
B. get the pump to Vagelis (my friendly and capable machinist) and tell him to fix it That will be most likely by building a new cover plate that is thicker "inside" effectively pressing the vanes top to bottom onto the casing and stopping the leaking, or fitting a bronze "ring" and pressing it inside

I know B is slightly controversial, but probably only cost me a tenner and may save me couple of hundred euros or more

any other opinions/experiences gladly received.

cheers

V.

 

[vas]

small update,

option A didn't work, none had anything remotely similar (and small!) around here.
So got it to Vagelis, took it apart, identified a shot bearing and will do a full rebuilt (bearing, seals, maybe reprofile the cam and possibly a thicker bronze washer at the bottom where the impeller sits. He also found out that the axle is worn, so he's either redoing it or welding and latheing it true again.
Looks like a lot of work, hopefully wont be over 40euro and I'll have a new pump.

cheers

V.

 

[vas]

to close the thread.

Vangelis called me to say that the shaft is shafted so had to fabricate a new ss shaft with the right tapers, key hole, pulley flat end to lock, threads et al.

Two bearing and a seal later, plus all his work, I got an effectively new pump back.
Bearings where really shot and seal probably never replaced leaking water that went to the bearings...

NOTE: if you blow or suck on the one end, yes the air comes through the other side, doesn't seal as I've seen bigger pumps do, go figure. But it works!
So if yours is not pumping, remove impeller and check for play carefully I didn't!

15euro for spares, 45euro for his work means I've got my genny working with a fully rebuilt pump for 60euro.
Hadn't realize that at 1000h this could happen tbh.

Now wonder where the heck the anodes are for this little engine!

cheers

V.

 

[vas]

always allowed to revive a thread you started

so, a year and a half later and probably no more than 20h on the genny, no water coming out of the exhaust again. Removed pump, pulley rotates suspiciously easily, open up, pulley and shaft rotates, but not the impeller. Remove impeller, no key to be seen anywhere. Realised that I've used a ss key (the only I could find!) on a bronze pump housing.
Fizzed away?
probably, new key built out of stock bronze, we shall see how it performs two years down the road.

cheers

V.

PS. still haven't bothered with the anodes, will try over the w/e