How a Looper Works va. Cross-Flow

[Skools Out]

for the questions on loopers here's ya some info

[THEFERMANATOR]

The short story is a crossflow uses ports directly opposed and uses a deflector shaped dome piston to direct the incoming and outgoing charges. Loopers use a flat top or nearly flat topped piston and uses the port locations to direct the incoming and outgoing air charges. Since loopers rely on airflow to move teh air where it needs to go, they are less efficient at low RPM's where air speed is lower. As teh RPM's increase though, air speed increases and allows teh porting to work as designed in a more efficient manner. Cross flow engines with there design utilizing the piston shape is more efficient at low RPM's than a looper is. Cross flow engines are normally used in applications where they need alot of bottem end torque and good idle characteristics like smaller kicker motors and such. OMC really changed the game when they came out with the first loopers, and revultionized outboards at the time.

Then there is the type of porting used in many chainsaws, but I won't even go into that one.

[smokeonthewater]

can't help ya on the carb question but fyi it isn't a "wise tale". The term is "wife's tale"

as for how to ID the design..... Just the other day I was shining a light into the spark plug holes on my merc and looking at the ski slopes on the pistons

[THEFERMANATOR]

Originally Posted by smokeonthewater

can't help ya on the carb question but fyi it isn't a "wise tale". The term is "wife's tale"

as for how to ID the design..... Just the other day I was shining a light into the spark plug holes on my merc and looking at the ski slopes on the pistons

Most loopers will not have removeable covers over the intake ports whereas every crossflow I have seen will have a removeable cover over the intake ports. Also crossflow engines tend to have a smoother idle with a slight rattle sound to them whereas a looper will have a lope to it like it has a big camshaft(unless it is a direct injected engine).

[spareparts]

Ferm and Skools, ya'll just showin off now

[bgreene]

The various " they " out there say the Evinrude 150 hp looper from the mid 90's era was one of the best outboards ever made.

[spareparts]

it may be, but good luck trying to find a set of carb bodies for it reasonably, more hard to find parts to follow

[BigHE]

I was just about to Google this...and here it is. Good info.

[Destroyer]

Originally Posted by BigHE

I was just about to Google this...and here it is. Good info.

Generally speaking, if it has something to do with V20 boats, or the engines that push them, you'll be able to find it here.

[jasoncooperpcola]

Originally Posted by Destroyer

Generally speaking, if it has something to do with V20 boats, or the engines that push them, you'll be able to find it here.

This site is the best tool in my box.