Simple Question, Complex Answer

[LuckyPenny]

Why do mairne engines (i/o) vent the valve covers back to spark arrester/air filter rather then utilize a PVC valve to the intake manifold?

 

[Don S]

Re: Simple Question, Complex Answer

It works, and is very uncomplicated. Nothing to stick or go bad.<br /><br />Well, that's my opinion anyway. Like any other "Why" question, we are not privy to why engineers do anything. So we deal with what they give us.

 

[trog100]

Re: Simple Question, Complex Answer

with cars cos of emission controls it has to be a sealed system.. with boats it dosnt so they have done it the way they have always done it.. the easy way.. the pvc valve a relatively recent way of doing it.. nothing on a boat is "recent" even relatively.. he he he<br /><br />trog

 

[Reel Poor]

Re: Simple Question, Complex Answer

Pcv valve require high manifold vaccum to work. Marine engines are practically always under extreme loads witch reduce manifold vaccum. Therefore a pcv valve does not operate properly. So as the engine builds crankcase pressure it must be vented somewhere. To keep these gases out of the bildge they are piped to the flame arrestor where the air flow into the carb/air intake can suck them in to be burned and exhausted.<br /> Some of the newer engines do have pcv valves but they are not equivelant to automotive design, although they look alike.

 

[LuckyPenny]

Re: Simple Question, Complex Answer

Question: in stead of venting to the carb, is it legal to vent the crankcase overboard? I am just tired of cleaning the flame arrester and carb.

 

[Bondo]

Re: Simple Question, Complex Answer

I am just tired of cleaning the flame arrester and carb.

Is That Excessive Blow-By,......... <br />Or,.....<br />Just being anal about a Really Clean motor,...????.......

 

[LuckyPenny]

Re: Simple Question, Complex Answer

Both, I think. how much blowbye is excessive? And yes, I am anal about keeping my engine clean.

 

[Haut Medoc]

Re: Simple Question, Complex Answer

Pretty sure the maint. is 100 hours or so....I generally do mine once in the beginning of the season & once in the middle......If you do have blow-by there is nothing you can do about it....A compression test will tell you what's happening.....BTW, GO TO BED! & Merry Christmas....JK

 

[trog100]

Re: Simple Question, Complex Answer

with the engine in good condition there shouldnt be much coming out of that valve anyways.. my engine is pretty old and nothing much comes out of the vent.. at least not messy oily stuff.. i dont suppose it would be that big a job to mod how the vent attaches to the arrester and make it so as it goes right inside over the top of the carb.. that way all the oil fumes (if any) would get sucked straight back down the carb leaving no mess at all.. it is a trick i have done with older car engines in the past..<br /><br />trog<br /><br />ps.. an elbow type fitting in the top of the arrester right over the carb choke would do the job very easily.. just attache the vent tube to that.. no mess at all..

 

[Buttanic]

Re: Simple Question, Complex Answer

One advantage of a PCV valve is the vacuum on the crankcase helps prevent oil seeping past seals and gaskets. Unless you run wide open all the time there should be sufficent vacuum for the PCV valve to work.

 

[f_inscreenname]

Re: Simple Question, Complex Answer

The people I talk to think the PCV valve is the way to go. The hose to the F/A is a thing of the past and no maker does that anymore (except big block Mercruiser I think and that is supposed to change).

 

[jimmbo]

Re: Simple Question, Complex Answer

My 2002 VP 5.7 uses a PCV valve on one valve cover and a hose to the FA from the other.