I have been doing some maintenance on my Yanmar 3GM30 and am struggling with the fact that it doesn't have an air filter, the service manual says it should have a silencer and a foam filter as shown below. Plenty of comments on other forums that say you don't need one and just as many that say you do with most saying the genuine product is useless and after market is the way to go. I found Walker engineering in Brisbane do custom filters for Yanmar engines, anyone used them are there off the shelf products suitable for marine? I assume that the filter has been missing for a long time and for its age the engine doesn't use much oil and runs well as is. What are your thoughts brains trust?

Cisco you will be pleased to know that I have started stripping out that gigantic petrol compressor from the engine bay. Wasn't much point having the potential to fill dive tanks or use a hookah if you cant access the port side of the engine for service and repairs or even change out the fuel filter water separator!

Just from past experience with generators and marine diesels...and the advice from the most experienced diesel specialist I know.

You must have a filter....paper filters don't last as long - but work better...

Fit the biggest filter/ silencer system you can. Just make it easy to remove...not lots of bolts.

Good clean air and cool air is the best thing....snorkels on 4wd and trucks are not there just for water crossing. They get the air intake up higher where there is less dust, and the air does cool down on the way through. Cool clean air = more power.

Fitting big silencers...do make a big difference to the noise.

The best air cleaners were made back in the 50s example would be on a FC Holden for example they were oil bath and to service them you replaced the oil after cleaning the old oil out .
They went to paper elemets so they could take more dollars off the owners

I was surprised how much additional noise was apparent when the cover on the inlet filter on my 2GM was a not quite properly seated. Also, there is a surprising amount of dust always settling inside my boat, both wind-borne and old bits of flaky paint etc etc.

So based on my experience, I'm voting in favour of having an effective filter. Yanmar did go to the trouble of designing and providing it in the first place.

Cheers, Graeme

Fitting a petrol dive compressor in the engine room sounds divine! what are you going to do with it?

Place the air intake down as low as possible so it sucks up the cold air from the bilge. Have a vent at the top of the engine bay so heat can escape. Real marine engines did not use filters, they just have inlet pipes down to a couple of inches off the bilge water. Dust settled into the water and the engine sucked up cool dense air.

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Ramona said..
Place the air intake down as low as possible so it sucks up the cold air from the bilge. Have a vent at the top of the engine bay so heat can escape. Real marine engines did not use filters, they just have inlet pipes down to a couple of inches off the bilge water. Dust settled into the water and the engine sucked up cool dense air.

You are right Ramona. The cool dense air from down low is great for the engine. My only concern with that is, if (when) the bilge pump switch fails, the engine will soon be sucking up bilge water.
I keep my air intake above my backup bilge pump for that reason.

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southace said..
Fitting a petrol dive compressor in the engine room sounds divine! what are you going to do with it?

If you do a lot of diving it is divine if you have the space for it.
In Wander66's case it totally occupies the cockpit locker severely restricting engine access and taking up valuable storage space. The yacht is a Carter Passage (centre cockpit) 33 so on a yacht that size you have to consider whether you really want it.

It is beautifully fitted but can't be removed in one piece. Good job Wander66.

Re air filters. I agree with what all have said. It is better to have one than not. The standard Yanmar filter/silencers are probably not very efficient but they are simple and easy to service with no tools needed and the intake can be directed to nearly any angle. Rather than fitting a modified filter I would just make sure the element and it's support frame are in top condition.

Thanks for the advice everyone I think I will go with the factory silencer and buy two filters so I can swap them out as required. Good idea about getting heat out the engine bay, the 6" diameter air intake for the compressor is already set up as a snorkel into one of the open storage compartments in the cockpit so it wouldn't be hard to fit a computer cooling fan to it and wire it to the ignition. The extra storage room will come in handy, the compressor was strapped to a reasonably study wooden frame so I will leave that in place and strap in a space case with spares and tools that can slide out as required.

I will definitely be selling the compressor SA it is 185 l/min twin tank powered by a Honda GX 160 plus oil separator and carbon filter. You gotta love those Honda motors, done nothing since May 2015 and started half way through the first pull.

The walker airsep has the added advantage of creating a negative crank case pressure, helping to reduce oil leaks. Worth a look from what I've read but not from direct experience

I am really intrigued by the idea of routing the air intake from down in the bilge. How many have this arrangement on their boat?

How can you guarantee water wouldn't be sucked up, say if you're motoring into heavy weather with the boat pitching around? Or if there's a leak or bilge pump or switch failure?

I'm more than happy to trade off any tiny theoretical bit of engine efficiency to keep water right away from my engine's intake!

Cheers, Graeme

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wongaga said..
I am really intrigued by the idea of routing the air intake from down in the bilge. How many have this arrangement on their boat?

How can you guarantee water wouldn't be sucked up, say if you're motoring into heavy weather with the boat pitching around? Or if there's a leak or bilge pump or switch failure?

I'm more than happy to trade off any tiny theoretical bit of engine efficiency to keep water right away from my engine's intake!

Cheers, Graeme

The normal routine on a power boat is to have air routed down to the bilge via a pipe from a scoop in the upperdeck. At the rear of the engine bay at the top there is a vent for the hot air to escape. Most of the time the hot air rising is enough to suck in cold air. In a yacht where the engine is usually tiny and not used continually the cold air is sucked in through the cabin limber holes and vents in the bilge and probably the hot air escapes through the cabin hatchway.

Now that you mention moving air through the bilge that might have been what someone was trying to do on my boat once upon a time. In the sole over the bilge and in front of the mast are slits that let air in from the cabin and under that was a rusted out computer fan. I had always assumed that it was an attempt to draw air out of the bilge so as to keep the mast step drier but it might have been going the other way through the bilge and into the engine bay. If I draw air out of the engine bay via the old air intake it will do something similar without having a fan exposed to bilge water. Still like the idea of a physical barrier on the intake as well though.