Broken screw on Volvo Penta impeller pump housing

[bankofdad]

Hi all had a bit of raw water ingress at the weekend - it filled the sump under my VP D2 when I had to gun it to get into Portsmouth in the face of the last part of an ebb tide.

Upon inspection & running engine to find the leak a painted brass screw had broken at the top. I tried to screw in a temp replacement from stocks on board but thread has also gone and with a bit of original left in.

As a temp fix I epoxied the hole leaving the remaining screw piece still in place behind the epoxy.

It held absolutely fine and no more water entered the boat on the return trip.

What does that screw actually do for a living?

I’ve found references to buy one but no actual context to what it does.

Also now I’ve filled with epoxy presume I’ll be looking at a whole new housing.

 

[lektran]

I'd say it is holding the raw water pump's cam in place, the piece that compresses the impeller fins as they rotate.

 

[PabloPicasso]

Drill out the epoxy and brass screw, re tap the thread, put a new screw in.

Helicoil, or drill out oversize and put a bigger screw in after cutting a new thread.

Surely it just holds the cover plate on?

 

[bankofdad]

I'd say it is holding the raw water pump's cam in place, the piece that compresses the impeller fins as

I'd say it is holding the raw water pump's cam in place, the piece that compresses the impeller fins as they rotate.

Ah yes of course that makes total sense.

 

[bankofdad]

Drill out the epoxy and brass screw, re tap the thread, put a new screw in.

Helicoil, or drill out oversize and put a bigger screw in after cutting a new thread.

Surely it just holds the cover plate on?

I think lektran is 100% right and it screws into cam so q is risk it for the sail planned this weekend as won’t have time to attend to it until next week. It was dry as a bone under there after return leg Sunday.

 

[scottie]

Cam screw is essential and needs immediate attention
If the cam rotates no pump action no water no cooling
You may be able to renovate if not it’s a new pump likely as body is not usually a separate part but worth checking

 

[bankofdad]

I had a 1 hr run on engine after dropping sails on return to my mooring & was pumping ok presuming epoxy I pushed in has bonded round broken part of screw still holding cam

 

[scottie]

Your choice your responsibility but !

 

[bankofdad]

Your choice your responsibility but !

Absolutely fair comment!

 

[bankofdad]

Dont think I'll attempt to refurb - I'll replace the whole thing. £550 because of one poxy brass screw....

 

[philwebb]

I agree with Scottie, what you have done was OK for a quick fix, but you need to dismantle the pump and do a more permanent repair.
If the small cam piece comes loose in the pump it could do a bit of damage and your engine will overheat in short order. Sod’s Law says that you will lose engine in an awkward situation.

 

[Stemar]

If I've understood correctly, it's the head that's come off. The rest of the screw is in the cam and the body, just the same as it was while the head was attached. If that's the case, I doubt very much if anything's going to shift.
However

Your choice your responsibility but !

Dont think I'll attempt to refurb - I'll replace the whole thing. £550 because of one poxy brass screw....

A tightwad writes...
If you take the pump off and remove the impeller, you may find that the cam will come out from the inside with the remnants of the screw. A bit of persuasion with a punch from the outside may help. It should then be possible to get the screw out. If not, a small bolt remover may work.

 

[bankofdad]

If I've understood correctly, it's the head that's come off. The rest of the screw is in the cam and the body, just the same as it was while the head was attached. If that's the case, I doubt very much if anything's going to shift.
However



A tightwad writes...
If you take the pump off and remove the impeller, you may find that the cam will come out from the inside with the remnants of the screw. A bit of persuasion with a punch from the outside may help. It should then be possible to get the screw out. If not, a small bolt remover may work.

Correct only head and a couple of mm of thread came away - will also need to drill epoxy out as i didnt mess about filling it up Although a punch might well knock it out

 

[philwebb]

If you can’t fix it yourself, you could take it to Portchester Engineering. They will do you a quality repair much cheaper than the cost of the new part.

 

[VicS]

Dont think I'll attempt to refurb - I'll replace the whole thing. £550 because of one poxy brass screw....

Replace the whole pump if you really want to get rid of £550 but refurbish the old one and keep it as a spare. The only part you will need is a new screw and perhaps a fibre washer under its head.
Once the impeller is removed I'd expect the cam plate and remainder of the old screw to be easy to remove. The you will then be able to remove the broken screw. Maybe you'll have to drill it out and clean up the thread but if there is enough protruding you'll be able unscrew it.

 

[pete]

If you do replace the screw brass is not ideal, bronze would be a better. Brass will do though if you remember to replace it every so often as it will eventually dezincify if in contact with salt water.

 

[scottie]

Replace the whole pump if you really want to get rid of £550 but refurbish the old one and keep it as a spare. The only part you will need is a new screw and perhaps a fibre washer under its head.
Once the impeller is removed I'd expect the cam plate and remainder of the old screw to be easy to remove. The you will then be able to remove the broken screw. Maybe you'll have to drill it out and clean up the thread but if there is enough protruding you'll be able unscrew it.

Agreed this is likely my main concern would be doing nothing but to do it I would think it would be easier with the pump removed
Is it possible that an agent can dissolve the repair ?

 

[Poignard]

Your decision whether to trust it.

I wouldn't.

I would follow VicS's advice [post #15] .

If you can't easily remove the remains of the broken screw from the cam, and you can't get anyone to do it for you by this weekend, when you want to go sailing, you could buy a new cam, screw, and washer from ASAP Supplies Ltd (if they have them); they deliver pretty quickly.

Fit them and you're in business

 

[TwoFish]

Replace the whole pump if you really want to get rid of £550 but refurbish the old one and keep it as a spare. The only part you will need is a new screw and perhaps a fibre washer under its head.
Once the impeller is removed I'd expect the cam plate and remainder of the old screw to be easy to remove. The you will then be able to remove the broken screw. Maybe you'll have to drill it out and clean up the thread but if there is enough protruding you'll be able unscrew it.

Which is exactly what the skipper decided to do on a barge engine I was working on. In this case it was a brass cover screw that had snapped off. Once I removed the old pump I found it remarkably easy to drill out the broken screw, using a left handed drill bit. I was expecting a pig of a job, but two or three mins to setup and drill a small pilot hole in the broken screw and then a few turns with the left hander and the old screw popped out.

 

[Plum]

Hi all had a bit of raw water ingress at the weekend - it filled the sump under my VP D2 when I had to gun it to get into Portsmouth in the face of the last part of an ebb tide.

Upon inspection & running engine to find the leak a painted brass screw had broken at the top. I tried to screw in a temp replacement from stocks on board but thread has also gone and with a bit of original left in.

As a temp fix I epoxied the hole leaving the remaining screw piece still in place behind the epoxy.

It held absolutely fine and no more water entered the boat on the return trip.

What does that screw actually do for a living?

I’ve found references to buy one but no actual context to what it does.

Also now I’ve filled with epoxy presume I’ll be looking at a whole new housing.

Agree with the others, just fit a new cam eg. Jabsco 490 Pump Cam Plate for Flexible Impeller Pumps but use a stainless screw. To remove the epoxy just heat the local area with a soldering iron which will soften the epoxy so you can just push out the remnants of the screw. The thread is in the cam so its only a plain hole in the body. Use a drill bit to remove any remaining epoxy. Seal the new screw to stop water leaking.

The Johnson pumps I have come across have a 8-32UNCX8 cam screw so do not assume metric just because the cover plate screws are metric. What is your pump Johnson model number?

Www.solocoastalsailing.co.uk