No air filter - is this normal?

Rivers & creeks

Rivers & creeks

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I read Andrew Simpson's diesel engine handbook and I'm gradually going over the engine checking it matches his description of what it should be like. But I can't find an air filter, there is a removeable mushroom shaped dome over the air intake with a very large guage wire gauze, the holes are so big it wouldn't stop dust, let alone fibres going in. Should there be a fine air filter in the 'mushroom'? The engine is a 75hp Thornycroft 245.

Thanks for your advice.
 
No real need on a boat installation. Would be different on a road vehicle and particularly a construction application where there would probably be a remote oil bath cleaner. Both my "modern" engines (Nanni and Volvo/Perkins) have just a foam pad on the air intake.
 
Tranona said:
No real need on a boat installation. Would be different on a road vehicle and particularly a construction application where there would probably be a remote oil bath cleaner. Both my "modern" engines (Nanni and Volvo/Perkins) have just a foam pad on the air intake.
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Thanks for the reply. A foam pad would stop big dust and all fibre particles - this is more like chicken wire!
 
Yes, quite common on older engines. Not much muck in the engine bay of a boat. If its any consolation foam looks like new even after years of service.
 
The Lazy Kipper said:
I read Andrew Simpson's diesel engine handbook and I'm gradually going over the engine checking it matches his description of what it should be like. But I can't find an air filter, there is a removeable mushroom shaped dome over the air intake with a very large guage wire gauze, the holes are so big it wouldn't stop dust, let alone fibres going in. Should there be a fine air filter in the 'mushroom'? The engine is a 75hp Thornycroft 245.

Thanks for your advice.
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Marine diesels like my old Gardner 6LW do not have airfilters. The air intake is usually a pipe set just above the bilge water. The cold air in the engine room is delivered by an air intake to just above the bilge water and the theory is any dust is collected in the bilge water. The warm air from the engine and exhaust is removed by a vent high up in the rear of the engine room so really there is no need for a filter except a wire gauze.
 
I had an engine with no filter so I fitted a K&N type, quite expensive but very good. They simply slide onto the stub and fasten with a jubilee clip. They are supplied with a bottle of gloop to coat them with, which gives them the properties of a tack rag! Although expensive, they can be washed out and recoated. As it was only a 13hp engine all it needed was a filter designed for a breather.

Rob.
 
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rob2 said:
I had an engine with no filter so I fitted a K&N type, quite expensive but very good. They simply slide onto the stub and fasten with a jubilee clip. They are supplied with a bottle of gloop[ to coat them with which gives them the properties of a tack rag! Although expensive, they can be washed out and recoated. As it was only a 13hp engine all it needed was a filter designed for a breather.

Rob.
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Did you notice any quietening effect from it? I've been thinking of putting a K&N on a VP2020 in place of the standard thin sponge one to reduce induction roar. The later D1-20 has a proper air filter and VP claim it cuts noise.
 
I didn't really do any comparitive tests before and after fitting the K&N, but there was no noticeable induction noise when running. I guess it took the edge off any whistle or roar, but probably no better than a boxed foam job.

Whilst on the related subject of engine box design, one set of advice is to fit vents in and out to cool the area and provide combustion air and the other is to seal it for sound-proofing and fire-proofing. Anyone got any brilliant ideas on how to meet both sets of criteria?

Rob.

P.S. Interesting... Correcting typos in a post doesn't carry over into a quotation in a later post.
 
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Troubadour said:
Did you notice any quietening effect from it? I've been thinking of putting a K&N on a VP2020 in place of the standard thin sponge one to reduce induction roar. The later D1-20 has a proper air filter and VP claim it cuts noise.
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I always put an air filter on. There are filters similar to KnN, or there are usually a few in the autobreakers, attached to wrecked boyracers (my ex stepson supplied me with go faster filters on a regular basis)
 
Sea Gull Catcher

Ford Sabre are the same, a large chicken wire mesh, that was delightfully refer to as a sea gull catcher, on their owners course many years ago.
 
rob2 said:
Whilst on the related subject of engine box design, one set of advice is to fit vents in and out to cool the area and provide combustion air and the other is to seal it for sound-proofing and fire-proofing. Anyone got any brilliant ideas on how to meet both sets of criteria?
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I am in the same situation. You (we) need an acoustic labyrinth so the air can pass but the noise bounces off the insulated walls and is attenuated as it transits.

There seems to be a lot of contradictory advice in the available documentation.

It would be nice to tackle the fire risk by being able to shut off the air feeds to starve the fire (and then add CO2). Then the engine would stop which might cause another problem. But you could feed the engine intake separately………………where do you stop!?
 
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