Fitting Jabsco sea water pump to Perkins 4108

[pcatterall]

I need to replace the seal in my pump.
I have previously read that getting the pump back on was a bit of an issue and that some kind of tool was required.
I did not fully understand the written discription at the time.
Now, with the pump off I cant see what the problem could be. There just seems to be a 'keyway' at the end of the shaft which presumably just locates on a key in the engine??
My instinct is that I just need to line them up pretty well by eye, offer the pump up and just twist it slightly until it engages on the key.
There would not seem to be an issue if the key located 180 degrees one way or the other?
Am I missing something?
As an aside am I correct in thinking that there is a replaceable seal at the back of the pump?

 

[RichardS]

I agree, although I don't have that engine. If the key is not offset, it will fit either way. If it is offset, it will only fit one way but it will be obvious that the bolt holes don't line up properly. There will, indeed be two seals ... one to keep the oil in the crankcase and one to keep the water in the pump with the springs facing outwards towards the oil and the water respectively.

Richard

 

[Roberto]

The pump is attached to a sort of circular metal support piece, which is in turn bolted to the engine.
If you detach the pump from the metal support there is no problem in bolting it back, if you unbolt the metal support you will need the Perkins alignment tool or something to put it back.

 

[pcatterall]

The pump is attached to a sort of circular metal support piece, which is in turn bolted to the engine.
If you detach the pump from the metal support there is no problem in bolting it back, if you unbolt the metal support you will need the Perkins alignment tool or something to put it back.

I don't really understand this ( despite it sounding like the information that I had read before!)
The unit I photographed is actually a spare as I have yet to remove the one I want to repair. Just looking at the one in the photo, which is complete with the 'support piece ' you refer to, I cannot see why it needs a special tool to fit it back on. The 'support piece' seems to be just acting as a spacer? My manual here doesn't cover this pump but the one on board ( in Spain) does. I will have to do some more delving!

 

[Motor_Sailor]

The centreline of the pump shaft must be exactly inline with the centre line of the camshaft. If not the drive dog we be eccentric and will move laterally with each revolution and cause wear.

The pump is mounted on that circular plate (in the photo) which in turn is mounted on the timing chain cover. Neither of these is a good fit and the 'play' in the mounting bolt holes allow it to be mounted several millimetres in any direction. The alignment tool guarantees that the timing chain cover and the circular mounting plate are replaced in exactly the right position.

However if you remove the pump from the circular plate, and leave that plate in situ on the timing chain cover, then the pump can be replaced without disturbing the alignment.

 

[DownWest]

The centreline of the pump shaft must be exactly inline with the centre line of the camshaft. If not the drive dog we be eccentric and will move laterally with each revolution and cause wear.

The pump is mounted on that circular plate (in the photo) which in turn is mounted on the timing chain cover. Neither of these is a good fit and the 'play' in the mounting bolt holes allow it to be mounted several millimetres in any direction. The alignment tool guarantees that the timing chain cover and the circular mounting plate are replaced in exactly the right position.

However if you remove the pump from the circular plate, and leave that plate in situ on the timing chain cover, then the pump can be replaced without disturbing the alignment.

What he said.

The double row ball bearing in the pump is not supplied by Perkins any more, but can be found from specialist outfits. A seal kit is quite cheap.

 

[pcatterall]

Thanks all. Fortunatly I have not removed the unit that requires the new seal, so I will remove the pump from the plate. I may get a better idea of how the referred to eccentricity is introduced as ( just looking at what is in front of me) there would seem to be little potential movement possible in just bolting it back ( 4 holes in plate 4 studs on engine).
If nothing else this rebuilding exercise has made me much more aware of how to fix things on the engine in place aided by the fact that access is slightly easier with the one in the garage !!

 

[Motor_Sailor]

. . . there would seem to be little potential movement possible in just bolting it back ( 4 holes in plate 4 studs on engine)

Yes, most of the 'sloppiness' is in mounting the timing chain cover to the block.

But it's still good practice to separate the waterpump from the engine by releasing its own mounting bolts and leaving the circular plate attached to the timing case cover. Then you have a machined, interference fit for the water pump to slide into.

 

[pcatterall]

Yes, most of the 'sloppiness' is in mounting the timing chain cover to the block.

But it's still good practice to separate the waterpump from the engine by releasing its own mounting bolts and leaving the circular plate attached to the timing case cover. Then you have a machined, interference fit for the water pump to slide into.

Cheers, yes I can see that. I believe that I can get a part kit from parts4engines which includes the 'nitrile washer and spring' which fits behind the impellor. Twenty odd quid which gets me a spare impellor as well.

 

[coopec]

I bought a new pump for my marinised 4 108 and had no trouble buying parts.
https://www.parts4engines.com/perkins-4-108-water-pump-kit/

Are you aware that Perkins never had a marinised 4 108 engine? They used to sell the standard 4 108 engine to jobbers who marinised the engine to their own design. If you look at these photos you can see a number of different versions.
https://www.google.com.au/search?q=...87XiAhUA7nMBHep_D3wQ_AUIDygC&biw=1055&bih=587

 

[Motor_Sailor]

Are you aware that Perkins never had a marinised 4 108 engine? They used to sell the standard 4 108 engine to jobbers who marinised the engine to their own design. If you look at these photos you can see a number of different versions.]

That's not true. Perkins themselves produced several different versions of the marinised 4108.

 

[pcatterall]

The photo link shows the Perkins 4108M. My Manual is from Perkins and deals with 4108M calling it the 'marine version'.

 

[PCUK]

I had to remove my pump on numerous occasions due to the slotted fitting on the end constantly breaking. There is no problem and no offset when fitting. Just make certain that the slotted piece almost bottoms out on the drive spigot on the engine otherwise the slotted piece will break. (It was not until I had sold the boat that I discovered why the slotted part kept breaking).

 

[Motor_Sailor]

It was not until I had sold the boat that I discovered why the slotted part kept breaking.

The slotted part breaks because it is not aligned properly. If it is, they never break. Being misaligned means the slotted joint gets bent one way and then the other for each revolution, which being 1/2 engine speed is still over a 1000 times a minute. No wonder they break off. The alignment tool makes sure the adaptor plate is aligned properly when the timing chain cover is replaced.

It should be called the 'adaptor plate alignment tool' rather than the water pump alignment tool as once you have the timing chain cover and adaptor plate aligned, the pump can come off and be returned with no problem.

 

[pcatterall]

The slotted part breaks because it is not aligned properly. If it is, they never break. Being misaligned means the slotted joint gets bent one way and then the other for each revolution, which being 1/2 engine speed is still over a 1000 times a minute. No wonder they break off. The alignment tool makes sure the adaptor plate is aligned properly when the timing chain cover is replaced.

Makes sense!

It should be called the 'adaptor plate alignment tool' rather than the water pump alignment tool as once you have the timing chain cover and adaptor plate aligned, the pump can come off and be returned with no problem.