how to make it work?

If it has a switch for 4-6-8 then you could try it set for an 8 cyl. That
would account for the 2 stroke having twice as many firing cycles as a 4
stroke.

"RB" wrote in message

 > Any reason I can't use a 4 cyl automotive tach for my 4 cyl o/b motor?
The
 > auto engine is 4 cycle, and the boat engine is 2 cycle.
 >
 > I'm just wondering what it take to make it useable on the o/b.
 >
 >
 >> Stay informed about: how to make it work? 

Actually on a four stroke one pulse reads out as two revolutions at the tach, not
four. Whether a two stroke or four stroke, it takes a stroke up and a stroke
down the cylinder to rotate the crank one revolution. A two stroke fires every
time the piston comes up while a four stroke fires every other time the piston
comes up. But what you are saying is true, the error would be 2:1.

BinaryBillTheSailor@Sea++.com wrote:


 >
  > >Any reason I can't use a 4 cyl automotive tach for my 4 cyl o/b motor? The
  > >auto engine is 4 cycle, and the boat engine is 2 cycle.
  > >
  > >I'm just wondering what it take to make it useable on the o/b.
  > >
 >
 > 2 more cycles. The tach works by counting ignition pulses. In a 4 stroke motor
 > those pulses occur once in every four strokes per cyclinder, so 1 pulse reads
 > out as 4 revolutions on the tach. In a two stroke engine, they occur every
 > other stroke.
 >
 > BB
 >> Stay informed about: how to make it work? 

All the vent is for is to allow air to travel back and forth. By routing
extra hose and mouting a loop as high as you possible can, you will prevent
water from coming into the tank (if the vent is too low) and you will
prevent gas from coming out. You want the highest part of the hose to be
above the tank fill position. There is no such thing as too high.

--
Tony
My boats and autos - <a rel="nofollow" style='text-decoration: none;' href="http://t.thomas.home.mchsi.com" target="_blank">http://t.thomas.home.mchsi.com</a>



"RB" wrote in message

 > Any reason I can't use a 4 cyl automotive tach for my 4 cyl o/b motor?
The
 > auto engine is 4 cycle, and the boat engine is 2 cycle.
 >
 > I'm just wondering what it take to make it useable on the o/b.
 >
 >
 >> Stay informed about: how to make it work? 

Sorry about that. Got my replies mixed up. This should have gone to the
fuel sloshing posts.

--
Tony
My boats and autos - <a rel="nofollow" style='text-decoration: none;' href="http://t.thomas.home.mchsi.com" target="_blank">http://t.thomas.home.mchsi.com</a>



"Tony Thomas" wrote in message

 > All the vent is for is to allow air to travel back and forth. By routing
 > extra hose and mouting a loop as high as you possible can, you will
prevent
 > water from coming into the tank (if the vent is too low) and you will
 > prevent gas from coming out. You want the highest part of the hose to be
 > above the tank fill position. There is no such thing as too high.
 >
 > --
 > Tony
<font color=purple> > My boats and autos - <a rel="nofollow" style='text-decoration: none;' href="http://t.thomas.home.mchsi.com</font" target="_blank">http://t.thomas.home.mchsi.com</font</a>>
 >
 >
 >


  > > Any reason I can't use a 4 cyl automotive tach for my 4 cyl o/b motor?
 > The
  > > auto engine is 4 cycle, and the boat engine is 2 cycle.
  > >
  > > I'm just wondering what it take to make it useable on the o/b.
  > >
  > >
 >
 >
 >> Stay informed about: how to make it work?