Another raw water question.....

[Lorien]

Hi,

 

I've never really got my hands to grips with our BMC apart from a little basic maintainence.

 

In the absence of a manual, I just wanted to check something on the raw water side.

 

I have a stop valve on the pipe coming up from what I assume is the 'mud box'. Above this the pipe raises to what looks like a large pot with a butterfly fastener.

 

Is this where the filter/strainer is?

 

In two years we've never had a problem but only recently I've noticed the water emitted with the exhaust doesn't quite seem as powerful as before.

 

If I have to shut off and replace the pump, should I clean out any other items at the same time?

 

Thanks,

Jim

[The Bagdad Boatman (waits)]

You must be sailing in very clean water. The mud box is normally cleaned out every trip and more often if in a weedy area. Close the stop valve, undo the top of the mud box/weed strainer and clean it out, sometimes the inlet pipe can be blocked with mud and you have to poke it clean with the stop valve open. Check the condition of all the water pipes and replace if rotten also check the condition and tension of the fan belt.

[FadeToScarlet]

Hi,

I've never really got my hands to grips with our BMC apart from a little basic maintainence.

In the absence of a manual, I just wanted to check something on the raw water side.

I have a stop valve on the pipe coming up from what I assume is the 'mud box'. Above this the pipe raises to what looks like a large pot with a butterfly fastener.

Is this where the filter/strainer is?

In two years we've never had a problem but only recently I've noticed the water emitted with the exhaust doesn't quite seem as powerful as before.

If I have to shut off and replace the pump, should I clean out any other items at the same time?

Thanks,

Jim

Yes, the large pot sounds like the secondary strainer-

 

 

It's worth undoing it and having a look inside before you start the engine every time. I'd also want to check the mudbox pretty soon, if it's not been cleared.

[Mac of Cygnet]

I assume that your water passes through a heat exchanger in the engine - direct raw water cooling must be very rare on canals. I don't have a mudbox, but do have a large strainer which I usually have to clean out about once a week depending on weed, etc. Occasionally the inlet pipe gets blocked with with a stick or such, but I can tell when that happens as the exhaust note changes and no water comes out! It's best to stop immediately then, as the engine can overheat quite quickly.

 

If you've got away with not cleaning the strainer for two years, you're doing very well! But if cleaning the mudbox and strainer doesn't increase the flow, then it's possible that the raw water pump may need attention - the impeller and even shaft replaced. The gritty HNC plays havoc with mine - had to replace it twice so far.

Edited February 1, 2015 by Mac of Cygnet

[Lorien]

Hi,

 

Thank you for the help.

 

I'm quite shocked as we've not taken care of something we should have !!

 

I take it the mud box is the large compartment with a lid on it like the rear weed hatch?

 

What's the best way to clean it out?

 

Thanks,

Jim

[Bee]

Are you sure you actually have a mudbox? it sounds as though the stop valve may just be a seacock on the inlet pipe that rises to the filter. If so then you don't need to do anything except turn it off when leaving the boat and keep an eye on the jubilee clips etc. The filter just needs to be checked, personally I do it every couple of days when moving, a dab of vaseline on the big rubber washer will do no harm, if this is not airtight the pump will suck air and not water. I would check the impeller on the pump if you have less water circulating, it will be at the front of the engine and probably be belt driven. the flappy bits break off. If it is missing any then they will probably be found at the front of the heat exchanger. If this all sounds scary it really is not when you get down to it, Oh, there are lots of different impellers, don't throw the old one away till you get an identical one, now how did I know that?

[mrsmelly]

Blimey

 

You must be in bottled filtered water. The bit with the wing nut on is probably the strainer? It may be above water level and safe to undo? or there will be a stop valve below it. We clear ours at work on all three engines every sail and usualy find quite a lot of leaves, grass etc. This would otherwise get to the heat excahnger which although a simple task to clear on here access may be more difficult on a small boat such as a narrowboat.

Id whip it apart and have a squint toot sweet.

 

Tim

[Grebe]

And when you buy the new impeller - buy two. You will then have another handy and not be stuck somewhere remote with a silly breakdown.

[gazza]

I keep the old one and replace bi annually.

 

Been lucky not to trash an impeller yet, despite the best efforts of Well Creek.....

[Lorien]

Wow,

 

How has it worked for so long.

 

I'm not sure what we have tbh. We've got a large, tall box with a lid on top held by two fixings very much like the weed hatch.

 

It's quite tall, I've been trying to figure out how (if it needed cleaning) I'd get to the bottom!!

 

On the bottom is a pipe approx 2-3 inches maybe, this rises upwards. Just off the rise is the stop valve. The pipe rises I'd say just above the box and here is the strainer type looking pot.

 

Hope my description is ok?

[mrsmelly]

Wow,

 

How has it worked for so long.

 

I'm not sure what we have tbh. We've got a large, tall box with a lid on top held by two fixings very much like the weed hatch.

 

It's quite tall, I've been trying to figure out how (if it needed cleaning) I'd get to the bottom!!

 

On the bottom is a pipe approx 2-3 inches maybe, this rises upwards. Just off the rise is the stop valve. The pipe rises I'd say just above the box and here is the strainer type looking pot.

 

Hope my description is ok?

 

Yep thats about right. Close the valve and whip the top off, There is probably a removable sleeve strainer in there. Pull it out and get rid of the crud.

 

Tim

[Theo]

I, too, have been lucky. In 3500 hours of running I have never had to clean out the mudbox. I did once have a blockage but it was a colony of snails that had set up home in the gear box oil cooler. In hunting down the blockage I replaced the impeller and always keep a spare one.

 

N