Engine water filter

[robertt]

I got my boat in March this year, she has a reconditioned Yanmar 2GM20F engine which looks immaculate (reconditioned 2011).
I'm just learning about the engine and am trying to get to grips with basics like bleeding and replacing impellor etc
I just noticed that there is no filter on the raw water intake for engine cooling.
Is this a potentially serious flaw? Is this unusual? I wouldn't like any muck to get into the coolant around the engine head.
I imagine I could just cut the rubber pipe and stick one on?

Thanks for all advice, as ever

Robert

 

[aluijten]

If you have a saildrive then the engine manufacturers seem to think you don't need a strainer.

Volvo Penta says because you take the water from a deeper level, there will be little or no debris in the sucked up water.

Don't you believe it though, a raw water strainer is very advisable. When you mount one make sure the top of the strainer is a bit above the outside water level so you can easily clean it when the time comes.

Arno

 

[Tranona]

Quite common not to have a strainer. However, not difficult to install one. Have a look in the Vetus catalogue www.vetus.com and there is a section on choosing and installing a strainer. Where you install it depends on the layout in your engine bay, but the ideal is above the waterline immediately above the water intake, so you will need new hose from the seacock to the strainer and from the strainer down to the water pump. Make sure you check the size of your hoses (probably 3/4") because on some strainers the spigots are fixed sizes.

 

[mjcoon]

... When you mount one make sure the top of the strainer is a bit above the outside water level so you can easily clean it when the time comes.

Arno

Does that mean that you have to be sure that the pump will quickly re-prime if air gets in (leak or cleaning) and breaks the siphon?

Mike.

 

[oldbilbo]

It's remarkably easy for the cooling water intake to become blocked by e.g. a small strip of plastic sheet, some weed, a growth of mussels.... and the flow of cooling water to be stopped, which causes the impeller to fry with friction. That causes more expensive troubles 'downstream'. It may be both worthwhile and convenient to arrange the positioning of your new raw water filter so that you can easily see whether 'fresh' water is bubbling into it when the engine is running. I inserted a perspex viewport into a convenient panel for this purpose, on a boat that had suffered several 'impeller problems'.

One other convenience is that of being able to supply the impeller with cooling water from a bucket/hose arrangement when running the engine on the hard.

Be aware, from a previous post, that it is all too easy to misalign the sealing rubber O-ring which caps the filter bowl, which then causes air and not cooling water to be introduced to the impeller. That also leads to costly consequences.

Edit: As for provision of a raw water filter, while there are many sources, ASAP Supplies have an excellent reputation for being helpful and reliable.....

 

[vyv_cox]

Does that mean that you have to be sure that the pump will quickly re-prime if air gets in (leak or cleaning) and breaks the siphon?

Mike.

The supply to the pump is taken from the bottom of the housing and suction comes in at the top. So when taking the lid off for cleaning the water level remains high in the housing, providing a positive head for the pump. Even if the housing is only half full it doesn't take long for all the air to be pulled through the pump, restoring the water level to the top. An additional bonus is that when flushing the engine through ashore it is only necessary to remove the lid of the filter and top up the housing with a hosepipe as water is drawn down. Much less hassle than arranging a supply with a bucket in the cockpit.

 

[mainsail1]

My Volvo Penta Saildrive has not had a raw water filter for it's entire life of 16 years without any problem and the boat has been used a lot. If Volvo think it is unnecessary I would leave well alone.

 

[vyv_cox]

It depends very much upon where you sail/motor. When we transited the Canal du Midi we emptied our strainer countless times, full of leaves and debris. I doubt that much of it would have gone through the heat exchanger.

I understood that there was a filter at the inlet of a saildrive, down the leg?

 

[savageseadog]

I've used Yanmar saildrives for thirty years on a regular basis, mostly in dirty estuarial water without any additional strainer with no problems.

 

[Tranona]

My Volvo Penta Saildrive has not had a raw water filter for it's entire life of 16 years without any problem and the boat has been used a lot. If Volvo think it is unnecessary I would leave well alone.

But many (including all the Bavarias I have seen) are fitted with a strainer - supplied by Volvo as original equipment.

 

[robertt]

FWIW I don't have a saildrive, it's a conventional prop shaft setup

 

[viva]

I think a raw water strainer is a must. I have recently replaced a barrel type strainer with a higher mounted Vetus type with the clear plastic screw-on lid. It is so much better, I can see the water flow and any debris in the strainer and I can add antifreeze without having to rig up a hose and bucket. If you mount the strainer above the water line you get a siphon break too.