What is a looper?

[JnT]

See a lot of OMC motors referred to as loopers.What exactly does that mean?

[rmh77]

Fancy name for a BOAT ANCHOR:D

[JnT]

Don't be hatin!!:)

[quickonstep]

a looper is a omc that is "loop charged" with pistons that send the flame arc into a loop out the exhuast (i think) they make more power than xflow's on average, and have a little more aftermarket availble.

Charlie m or another omc guru will jump on this in due time

Jesse

[mr.clean]

Fancy name for a BOAT ANCHOR :eek: :eek: :eek:

[Bill H]

I'm glad you asked that JnT, I didn't have the nerve.

[MarkHP]

A looper or loop charged motor has intake porting to direct the incomming air/fuel mixture upwards into the combustion chamber and utilizes a flat topped piston. Whereas a cross-flow uses a scalped piston top to achieve the same desired flow with cobevtional porting. I believe, for the same size, the loopers develop more torque and are more fuel efficient than the cross-flows. Of course I am not an expert and if this is not right, please, someone correct me.

[JnT]

I'm here to learn. Thanks for the replies!

[Raceman]

All V6 Mercs are loopers, which is a more efficient design. Omc's were made in both configurations at various times.

[JnT]

Is an 87 Evinrude 225 a looper?

[neveredge]

Yes, And it is the bridgeport block and has the good heads. If you really want to wake it up, send it to Racer (Al Stoker) He can bore it to 3litres and finger port it. 300 HP is easy to obtain from these engines.

[ON THE HUNT]

Loop charging is a method of scavenging the cylinder of a two cycle engine. To make power we must have a fresh untainted charge of air and fuel. In a loop charged engine we have an exhuast port, two schnerle ports 90 degs to the exhuast port(one on either side of the exhuast port) and last but not least a boost port(and figerports where used). Look at the cylinder from the top and divide it into four pieces. The exhuast port is one piece of this pie,the schnerle ports on either side take up the next two pieces and last but not least we have the boost port directly across from the exhuast port. Spark plug sparks and starts the fire. The rapidly expanding gasses are pushing the piston Down the cylinder turning the crank. Somewhere past half way the exhuast port starts to open providing the expanding gasses away to escape and the piston continues downward. A few deg. of crankshaft rotation later the schnerles open which have been aimed away from the exhuast and up towards the cylinder head. The schnerles then fill the cylinder forcing the exhuast gasses into there piece of the pie,the piston is still traveling downward. Next acouple of degs after the schnerles open(for all the gurus out there this is basic schnerle port mapping) the boost port that is directly across from the exhuast port opens(and finger ports). The boost ports top edge(roof) is aimed towards the plug and its bottom towards the far edge of the combustion chamber. As the gasses from the boost port encounter the cylinder head the heads shape be it top hat or "hemi" turn the charge on top of the exhuast ports pie piece and ram it out insuring a fresh charge on the next power cycle. This could have been a Whole lot longer but thats the basics.

[JnT]

Neveredge,What would the mods you mentioned cost?

[INXS]

I checked with Al last fall, there are varibles, such as weither or not your pistons can still be used, how much HP you want, what octane you want to use, ect.. I think he said that for what I was looking at, about 265 HP? running 92 octane at about 6500 rpms, it would coast about $3k. I'm not 100% certain of these numbers but I think that's what it was. You can drop him a e-mail letting him know what your're looking for from your motor and he can send you some info.. From what I heard his motors are much better then production motors. I've a 88 225 Johnson which I plan on sending to him this winter. If you crunch the numbers your're find it's a bargin compared to going new or relatively new.