Air Filter

[Grant_West]

Ok I might not be using the correct name of it but its the metal flame arrestor in front of the air intake on the motor on a PCM 5.8 GT-40
I never thought that this was a mainteanace item. My mechanic said that this Air filter /flame arrestor was very dirty. And needed to be cleaned out. He said he shot like 2 cans of carb cleaner threw it and lots of black stuff came out. I know thats not good. And could cause poor air flow. Do you clean yours out every year along with oil and filter changes???

[Mikeski]

RE: Air Filter

There are not really that many sources for dirt under the motor box of the boat. One of the most significant source of the black powder is your fan belts. Since you have a high powered alternator and you drive it hard with lots of accessories you probably get more fine rubber dust lodged in the spark arrestor than most. My 1995's GT-40 spark arrestor looked like new at 560 hours which was the last time I serviced the boat before it sold. I tend to run the v-belts just tight enough to keep them from slipping so the bearings behind those pulleys last, but I was not pushing a 100+ amp alternator.

Luckily the black rubber powder is probably not very abrasive to the internal engine components. An extremely dirty air filter can cause an engine to run slightly richer but I doubt that the spark arrestor was clogged that much. It's probably a good idea to check it out every 100 hours or so. A clean engine is a happy engine.

[Hollywood]

RE: Air Filter

Please don't "clean" it out with compressed air. This is something a MC or Bu owner would do... Buy a new one.

[DanielC]

RE: Air Filter

It is a flame arrester. You do need to clean it. There is a hose that comes off of your oil filler tube that vents under the flame arrester, and over time it gets a light coating of oil on it. The oil then traps any dust that might get in the engine compartment. soak it in a solvent that dissolves oil. and then blow it out with compressed air, from the inside out. DO NOT DO THIS WITH THE FLAME ARRESTOR STILL ON THE ENGINE!

[jhiestand]

RE: Air Filter

I'm not sure how they get dirty either, but it's easily removed & cleaned with carb cleaner. Hitting it whenever you change oil should be plenty often.

[25xs]

Yes you clean it: No you don't replace it:

Newer fuel injected motors have more of an air filter on them than traditional carburated motors. There are K&N Marine replacement filters available for them that flow better than stock. "Spark Arrestors" that most of us encounter don't flow worth crap, but that's what we're stuck with. You need to keep them clean as new to get the most out of your boat. Better yet, stack two together if you're engine box allows the room and your intake will flow better.

A dirty spark arrestor can make a carburated engine run rich (black smoke, soot on the transom, rough idle, etc...) A dirty spark arrestor/air filter on a fuel injected engine will not make it run rich so much as just run poorly. Your air flow meter on a fuel injected engine measures the actual amount of air being drawn into the engine, so it compensates for a dirty spark arrestor/air filter by injecting less gasoline i.e. low power.

A performance K&N flame arrestor is about $100 retail for an EFI motor, a performance spark arrestor for carburated engines is about $200 retail. (Just got the new Livorsi Marine catalog yesterday :>)

The metal "spark arrestor" on boats is designed to collapse in the event of a fire. Mainly on carburated engines, it will collapse flat when the four rivet looking posts melt the wrinkled layered disks compress flat and snuff out the fire in the carb. I have only seen a few engines that burned, but all of them had flattened spark arrestors that performed right. The problem on those was that the fire was not in the carb. I have seen one Nautique that overheated severely and the spark arrestor was partially collapsed just from the engine getting so hot!

The best way to clean them is in a parts washer. If you don't have one, a cakepan filled with gasoline works and you clean the debris off the outside surface with a paint brush or similar item. Then shake off as much gas as possible and use compressed air, BLOWING FROM THE INSIDE SURFACE to the outside so you don't pack more debris into the filter disks where you can't see them and where the engine might end up ingesting them.

You don't replace spark arrestors, you clean them. They are WAY too expensive to just toss out and replace, but if anyone decides to do that I'll pay the shipping for you to send me your dirty spark arrestor!

[nms1991]

RE: Yes you clean it: No you don

Accually you can get a ticket from the coast guard if you have a dirty flame arrestor. Best way to clean the flame arrestor is to use mineral spirits in a parts tank an clean inside to out then blow inside to out also. If you have no access to a parts tank use either carb cleaner or brake cleaner, but do not do this on the engine or in a enclosed enviroment. Also look at it every time you check your oil and trans to see if it is getting dirty.

[25xs]

RE: Yes you clean it: No you don

Ya know, nms1991 makes a good point... Check the flame arrestor periodically and make it part of your routine. As stated in an earlier post, the v-belt dust is the most common clogging debris on a flame arrestor and it's produced in GREAT QUANTITIES if you fail to protect your v-belt pulley from rusting during long term storage. The belts wear off the factory paint and expose smooth, polished steel surfaces on the pulley's that will rust and pit during the winter months or even in the summer if your bilge area is not properly dried and ventilated when not in use. A quick shot of WD-40 will do wonders for belt & pulley life and although belts are cheap, pulley definitely are not cheap. Add a corrosion/rust preventative on the pulleys to your winterization list.
Tom

[ag4ever]

RE: Yes you clean it: No you don

WD-40 on the pulley????

I would think that would cause the belt to slip and wear a lot faster.

Also, I have not seen a marine engine with a mass air flow meter. Most are run off of set parameters since you can't put an O2 sensor in the exhaust.

[25xs]

WD-40 on the pulley... Sure.

WD-40 on the pulley????
I would think that would cause the belt to slip and wear a lot faster.
Also, I have not seen a marine engine with a mass air flow meter.

Sure, WD-40 won't make the belt slip if you only spray the exposed, bare steel section of the pulley that gets polished from belt wear... WD-40 isn't really a good lubricant anyway, it is technically a "penetrant" designed to soften old grease, penetrate rust, and foremost to disperse moisture. Don't go hog wild and have the engine dripping with WD-40, just coat the shiny section of the pulley so it doesn't rust during the off season.

Also, no one mentioned a mass air flow meter until 'ag4ever' did... But the fuel injected motors do take manifold air pressure readings from both sides of the throttle body and derive a mathematical mass air flow based on these pressures. This is combined with engine rpm to decide how much fuel to inject. If the air is restricted (dirty flame arrestor), the rpms won't increase and not as much fuel will be injected. Today's motors aren't quite as smart as a true mass airflow meter equipped motor, but they are ALOT smarter than a "speed/density" injector algorithm from the early 1980's.

This is splitting hairs, but I've replaced pulleys on a few MerCruiser I/O's and inboards due to rust on the belt drive vee section and it's not cheap... WD-40 or similar rust preventative sprayed on in the fall would have been cheap insurance for those customers.

[ag4ever]

RE: WD-40 on the pulley... Sure.

Your air flow meter on a fuel injected engine measures the actual amount of air being drawn into the engine

But the fuel injected motors do take manifold air pressure readings from both sides of the throttle body and derive a mathematical mass air flow based on these pressures.

In one you say measures the actual amount of air, then the nxt you say derive a mathematical mass air flow, not exactly the sam thing. That is why I asumed you meant a measured by means of a mass flow meter, even though it too is based on mathmatical computations. I guess what I am saying is you don't really measure the actual air flowing through an engine, but just calculate how much it should be flowing under the given conditions.