Mariner 2 hp water pump puzzle

[sharpener]

I have a Mariner 2M (6A1) which has served us well for 30 years, however yesterday it stopped because there was no cooling water flow at all.

On stripping the pump I found the two 4mm drain holes in the base of the cup completely blocked with hard white plastic, to which small bits of the impeller had stuck. The 6mm inlet hole was the same. I cleared them out with suitable drill bits and the impeller itself has only minor damage (but I will replace it anyway).

Can anyone tell me what the white plastic bit is and why it ended up blocking the holes? There is also a fourth elongated hole at the side opposite the inlet hole, what is the purpose of this and should I clear it out as well?

Thanks in advance!

 

[sharpener]

So I decided all the parts need replacing anyway and the spares have now arrived from BHG Marine. But the water pump insert cup is stuck very firmly to the plastic oil seal protector, it all seems to be welded together and stuck to the cast aluminium housing.

Is there a recommended method for getting these parts out?

It would be especially good to hear from @steve66 or @VicS with their extensive experience of these Mariner ouboards!

TIA, Chris

 

[alahol2]

I have a Mariner 2M (6A1) ...

On stripping the pump I found the two 4mm drain holes in the base of the cup completely blocked with hard white plastic, to which small bits of the impeller had stuck. The 6mm inlet hole was the same. I cleared them out with suitable drill bits and the impeller itself has only minor damage (but I will replace it anyway).

Can anyone tell me what the white plastic bit is and why it ended up blocking the holes? There is also a fourth elongated hole at the side opposite the inlet hole, what is the purpose of this and should I clear it out as well?

There's a photo of the inside of the water pump in this document. It looks like all the holes are 'blocked' by the white plastic cup. I can't see why you would need more than one inlet and one outlet hole.

 

[anoccasionalyachtsman]

Edited. If you've got a new stainless liner then it looks like it's a matter of getting a thin blade between metal and plastic and folding the liner away enough until you can get pliers onto it and pull it out. You probably need to do the same folding on the opposite side to get a second pair of pliers in.

My guess is that there are two lumps in the plastic that engage with the holes in the liner to help align it correctly, and to help stop it spinning in use,.

Before you do it though - do you want to put a picture up to let us judge whether it's badly enough scored to warrant changing?

 

[sharpener]

Thanks guys. Had already found your document @alahol2, really useful, though in the event I found it easier to separate the leg from the power head first. I suppose it depends where it comes apart most easily.

Back to the pump, yes I have been folding the cup inwards (with a cold chisel, in four places) to get something I can get a purchase on with pliers and/or tyre levers, so defo needs replacing now! (the base was domed anyway, don't yet understand exactly why) .

But still stuck, am about to fold it some more over the head of a big bolt and improvise a slide hammer on the shank of the bolt.

 

[sharpener]

Finallly got it apart by levering with the big bolt.

As you can see from the pix the base of the inner cup is badly distorted, I think by all the expanding corrosion products underneath, though there are also signs the nylon outer cup has been melted in places. The oil seal was coming apart and it's a small miracle it was still keeping the water out of the gearbox, so that needs replacing as well.



The big hole at the forward end is the inlet via the cavity in the base casting and the six intake holes in it. The two side (drain?) holes communicate directly with the outside world. There is a lug at the aft end of the steel inner cup which goes through the fourth hole in the outer cup and into a blind hole in the casting to prevent it all from turning round.