Seawater drain on Yanmar 3YM20

[CJ1]

Hi
In preparation for Winter I would like to drain the seawater from my Yanmar 3YM20.
I have found the drain cock, that has the appearance of a smooth metal disk, a bit smaller than a ten pence piece with a small hole in the middle.
But I can’t work out how to open it, nor what tool I should use to do this. Could anyone give me some advice ?

Many thanks.

 

[tross]

There are two places to drain the seawater from the system. The first is the pipe that goes from the raw water pump to the heat exchanger - which I think the one you are talking about. From memory it is a 7mm allen key to undo this. The second is a bleed nipple on the other end of the heat exchanger by the exhaust pipe - I think 10mm spanner on this. I added a length of tubing to this to make it easier to collect the water.

 

[CJ1]

Thanks for your reply.
Did you mean a 7mm socket spanner?
The draining cock I can see on the hose connected to the water pump, has a tiny - no more than one or two mm - hole in the middle. The water cock itself looks like a metal button. I can’t quite see how to get any purchase on it.

 

[VicS]

Thanks for your reply.
Did you mean a 7mm socket spanner?
The draining cock I can see on the hose connected to the water pump, has a tiny - no more than one or two mm - hole in the middle. The water cock itself looks like a metal button. I can’t quite see how to get any purchase on it.

What shape is the hole? Hexagonal? Will an Allen key not fit it ? I'd expect a metric one but you never know it might be Imperial

 

[RichardS]

Thanks for your reply.
Did you mean a 7mm socket spanner?
The draining cock I can see on the hose connected to the water pump, has a tiny - no more than one or two mm - hole in the middle. The water cock itself looks like a metal button. I can’t quite see how to get any purchase on it.

It is rather confusing but that silver button in the lower hose is an Allen fitting. I spent ages with a mirror down there because I wasn't convinced. It's metric and something like 3mm but you'll soon find out with trial and error. The moulding on the hose that the button screws into is only black plastic so it shouldn't be that tight.

Mine's a 3YM30 but it sounds like the same drain fitting. There's also the more conventional one on the side of the block near the oil filter plus the one on the elbow end of the heat exchanger.

Richard

 

[CJ1]

Thank you all for your feedback. I guess it is an Allen key type, with a very small aperture.

I can’t figure out how to attach a photo into this thread, otherwise I’d post a picture.

 

[VicS]

Thank you all for your feedback. I guess it is an Allen key type, with a very small aperture.

I can’t figure out how to attach a photo into this thread, otherwise I’d post a picture.

Click on the insert image icon on the formatting toolbar , then "from computer", then "choose file". Select the picture file, then "upload file"

 

[CJ1]

Here it is...

 

[RichardS]

View attachment 81501
Here it is...

As I said, 3 +/- 1 mm Allen key required.

Richard

 

[CJ1]

Thank you all for your advice.