K&N Marine Flame arrester

[TuxedoPk]

I was reading some of the old posts where members where stating that they were going to be trying these out.

Now that you've been running them for 2-3 years what is your take on them? Is it worth the money to upgrade existing flame arrestors? What are your overall impressions?

[Cuda]

I have K&N on my Formula. I don't like them at all. They are too flimsy. When I try to put the valve cover vent hoses on them, they tend to collapse the filter. Gaffrig is a much better rig.

[tmdog]

I believe that installing a K&N filter providing it is more than 2 inches high is the best upgrade and cheapest improvment you can make. Routing vent hoses thru the filter is not a good idea for performance sake. Route vent hoses to catch or puke tank and than have hose from top of can vented to outside of boat. Made one from a m-t quart paint can. I by far am not an expert on hi-performance but some things just make sense.

[Cuda]

They are hoses for the valve cover vents for crankcase ventilation. It's the way it's supposed to work. The filters are just so flimsy it pushes the filter in. The Gaffrig on the Donzi is MUCH better.

[Cuda]

You can see in this picture what I'm talking about.

[Cuda]

Here is the Gaffrig on the Minx. It's a much sturdier set up.

[tmdog]

Cuda, I know what you are saying, but-- I'm saying ther is a better way to vent. My method does not contaminate the air filter. Why run oil and fumes down the carb that don't belong there. If you want to constantly fog your engine and ruin the filtration system just do not make sense.

[Cuda]

By routing it through the carb is that it gives a slight vacumn and circulates fresh air through the crankcase, like a PCV valve does on a car. In the old days on cars, they ran a pipe out of the valve covers down the engine and turned it facing backwards to draw air through the crankcase. It was called a "road pipe". I'm not sure your method will circulate the air through the crankcase.

[Cuda]

This explains why the crankcase needs to circulate fresh air through it.
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Crankcase Ventilation
The crankcase is a collection point for a variety of materials or contaminants harmful to the motor oil and internal engine parts. Some materials found in the crankcase are abrasive solids such as dirt, sand, and metal particles. It is the responsibility of the oil filter to keep these abrasives from circulating to the friction surfaces and to keep the amount of wear to a minimum.
Other materials which collect in the crankcase, such as water, acids, and unburned fuel, may be in the form of either liquid or vapor. These materials are by-products of the combustion process. For example, when gasoline is burned in the presence of an adequate air supply, water is produced at a rate of about one gallon of water for each gallon of gasoline that is burned.

Most of the water and acids created as vapor in the combustion chamber are carried out of the engine through the exhaust. However, some of these vapors reach the crankcase as blow-by. This means that vapor is forced between the rings and the cylinder walls by combustion pressures which are as high as 700 lbs. per square inch. Blow-by occurs even with engines in good condition, but increases as engines become worn. Unburned fuel resulting from incomplete combustion may also enter the crankcase as blow-by vapor. Additionally, some unburned fuel may be forced into the crankcase on the compression stroke of the engine before the fuel/air mixture is ignited. Pressure in the combustion chamber during the compression stroke may be as high as 200 lbs./psi.

Water, acids, and unburned fuel may enter the crankcase in liquid form as well as vapor. These materials can condense on the cylinder walls and be washed into the crankcase with the motor oil. Even the materials which enter the crankcase as vapor do not remain in vapor form. As the engine cools, they condense on the internal engine parts in the motor oil. Certainly, water and other acids can severely damage internal parts by causing rust and corrosion. The motor oil additive must counteract the corrosives and keep the sludge-forming ingredients in suspension. Unburned fuel, when condensed, places an additional burden on the motor oil. Gasoline, in liquid form, affects motor oil additives and reduces the oil’s film strength. Dilution of motor oil with unburned fuels may also increase oil consumption.

Contaminants Cannot Be Prevented From Reaching The Crankcase
Therefore, the only way to combat the effect of these harmful materials is to vent them from the crankcase while they are in vapor form. In this regard, the temperature of the engine is a critical factor. As long as an engine is operating at normal temperatures, engine heat will prevent these contaminants from condensing. However, if these contaminants remain in the crankcase when the engine is stopped, they are condensed as the engine cools. The basic purpose of any crankcase ventilation system is simply to remove these harmful ingredients in vapor form at about the same rate in which they enter the crankcase.
The History Of Crankcase Ventilation
The problem of crankcase ventilation was recognized, and the first ventilation system installed, long before the current PCV (positive crankcase ventilation) systems were developed. In fact, the first crankcase ventilation system was installed in 1925. At that time it was referred to as a road draft tube system. The system used a vented oil filler cap and a tube which extended downward from the crankcase area to a point below the engine block. The lower end of the tube was open and exposed to the air flow when the vehicle was moving. At speeds above 20 MPH, the air passing over the open end of the tube created a low pressure area, or partial vacuum. This, in turn, caused a draft, or air flow, through the crankcase. Fresh air entered the crankcase through the vented oil filler cap, forcing vapor out through the road draft tube. The road draft tube system, although not effective at speeds below 20 MPH, provided adequate crankcase ventilation and remained in use until the modern PCV systems were developed.

[Forrest]

I like using a breather cap on one valve cover and a PCV valve on the other. Everything stays nice and clean that way. The only down side the this set up that I can see is that when running wide open there is so little vacuum through the PCV valve, the breather cap tends to "exhale" hydrocarbon "blow-by" into the engine compartment and the top of the valve cover gets a little oily - but the flame arrestor stays clean.

[txtaz]

Dang Cuda,
Don't hold back, give it to us straight, no holds bar.
Just kidding, thanks for all the info and history. You can never have enough good info.
Wes

[Cuda]

Dang Cuda,
Don't hold back, give it to us straight, no holds bar.
Just kidding, thanks for all the info and history. You can never have enough good info.
Wes

:)
I just remember vividly my dad giving me a lecture about crankcase ventillation when he saw rags stuck in the valve covers of my first car. :D

[MOP]

Rich why not just go for the Merc 3" tall one, my 86 has one its in perfect shape. Even on a bronze mesh cleaners you can use filter oil to catch more dirt, boats do not ingest much filth usually just belt dust. Just want to keep birds and small children from falling in the hole! :)

[Barry Phillips]

I read a test in Power Boat concerning KN filters in a marine application and no appreciable gains in HP or performace were made over a standard flame arester.

[Jim]

Well I had gone and purchased a K&N Air Filter from Rex Marine before really doing my research. I installed it a few weeks back and I didn't really notice too much gain, I do like the filter system better then what the OEM uses which is like a metal screen system but other then that it was $180 to make it look a little nicer. I have a 502 and tried to find a Harding Marine Filter but didn't feel like spending almost $300 so I went with the K&N.

Bryan T. had mentioned which I will confirm that the adapter K&N uses is actually a reducer which the K&N attaches to, if I had noticed that when purchasing it I would of not gone with it. It doesn't seem to make much sense to take a 3X4 rectangle air intake or whatever it was and narrow it down to like a 3" diameter hole. I did see the highest top end with my boat last night but I think that had more to do with the cooler weather and having less fuel in the boat.

Thanks Jim

[Pismo]

I got the Xtreme arrestor for CP performance. I did a test run 75.5mph on gps, changed to arrestor from stock to the new one did a run not 10 minutes later and got 75.5mph on gps.

On a 1996 22 Classic with a 502 MPI 27" labbed Mplus prop. My revs were only around 4700 tho and a friend said i did not have the revs to see any difference due to the new arrestor. Need 5000+, who knows...............

Cheers
SL

Save your money. Get a better prop instead.