{Stus-List} Yanmar YSB12 Air Induction Tube

[Rich Knowles]

A picture of your engine can be seen at:

http://annonces.romandie.com/annonces_photo_0_0_2516959xx69a22b65f23dc2932961a74d284e09cf.jpg

Many Yanmar engines were made for other than pleasure boats; tractors,  
fishing boats etc. The intake runner may have been designed to keep  
water and crap out of the engine or to keep the profile low. On a 12  
HP single cylinder engine, I can't see it's length or shape having a  
dramatic effect on performance. Try removing it and seeing how the  
engine performs under load. If it still works well, you could either  
modify the existing unit or have a new one made up to fit that would  
give you more clearance for the sink.

Rich Knowles
INDIGO LF38
Halifax, NS.




On 14-Jun-09, at 11:05 PM, Steve Thomas wrote:


Jake,

The air intake tube is made of cast iron, about 2 inches in diameter,  
and
curved into a vertical semi circle that ends up facing squarely aft.  
There
is no air filter and no provision for one. It always looked kind of  
odd to
me, that the air flow would be turned 180 degrees like that with no
obviously compelling  reason. I figured that it might be "tuned" for
performance within a particular rpm range. Maybe it is just to aim the  
noise
toward the stern.

The image in the link you provided is of a related but different engine.
The engine in the image has a vertical cylinder, while in the "YS"  
series of
engines, the cylinder is horizontal.

Thanks,
         Steve

-----Original Message-----
From: cnc-list-bounces at cnc-list.com
[mailto:cnc-list-bounces at cnc-list.com]On Behalf Of Captain Jake
Sent: Sunday, June 14, 2009 5:30 PM
To: cnc-list at cnc-list.com
Subject: Re: {Stus-List} Yanmar YSB12 Air Induction Tube


Steve,

As a general rule, the length of the induction tube (or whatever you may
call it) is usually not a critical dimension.  I am assuming you're
referring to the air intake tract, which leads to the air filter and
then the intake manifold.  I think I found a picture here:
http://www.ekstrom.fi/site/img/82.jpg

The intakes are usually tuned for optimum performance and minimum
noise.  Changing the length may alter one or both of these, but usually
not by much.  What material is the induction tube made from?  Sheet
steel, fiberglass, or something else?

Jake

C&C 35 Mk-III
Midnight Mistress
Hampton VA

Steve Thomas wrote:
> I would like to replace the sink in my 1978 C&C 27 with one that is
> deeper, but the semi-circular air induction tube on the engine is in
> the way. Does anyone know if this tube is has a critical length, or
> have you seen one of these style of engines in use with any other sort
> of air induction tube?
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