Looper vs. Crossflow

[Tcorum]

I have a 140 Johnson and I have been doing some reading but can't determine the difference between a looper and a crossflow. Can someone tell me how these motors differ in performance? Is one faster then the other or maybe more reliable? Also I would like to know how to determine which my motor is? The model number is 140TL78C so I would assume its a crossflow?<br /><br />Thanks<br /><br />Tcorum

 

[Franki]

Re: Looper vs. Crossflow

Well, without getting technical..<br /><br />A Crossflow has a wedge shape on the top of the pistons.. the incoming mixture gets deflected by that wedge upwards and pushes the exhaust gasses out.<br /><br />A looper achieves the same thing without the wedge.. uses the ports to "flow" the new mixture to the top of the head.. in a "loop" as it were..<br /><br />Loopers are supposed to be more efficient.. but I dont' think there is that much in it.... the main reason is that the pistons are much lighter without the wedge on them... and the combustion chamber can be more efficiently designed without taking the piston wedge into account.

 

[jegervais]

Re: Looper vs. Crossflow

You've got a cross-flow.<br /><br />-John

 

[wilde1j]

Re: Looper vs. Crossflow

I don't know if there is any inherent advantage from a power standpoint to a looper vs. cross flow design, but generally OMC 1984 and earlier measured HP at the bottom of the crank shaft, while newer motors measure HP at the prop shaft, which takes into account losses thru the gearcase. So, a newer 140 is naturally somewhat more powerful than the older ones due to where HP is measured. The delta is on the order of 5 to 10%. This was driven by the Japanese motors ... they always measured at the prop shaft.