View Full Version : How can you tell if an engine is counter rotation?

Scott Pearson
09-17-2014, 05:16 AM
I'm looking at some engines and they are a pair that came out of a Cigarette. Not sure if one is counter rotation. Is there a way to tell by looking at them on stands? They are 420 Mercruisers.

Any help would be great!

09-17-2014, 05:42 AM
Pull the valve covers, crank by hand, watch intake valves for firing order?

09-17-2014, 07:30 AM
When you put it in reverse and the bow slams into the dock??

09-17-2014, 07:32 AM
Check distributor wires for which direction it's spinning to get the right firing order.

09-17-2014, 07:41 AM
When you put it in reverse and the bow slams into the dock??



09-17-2014, 08:00 AM
inlet and outlet hoses on the sea water pump shouldn't match

starter drive teeth angle shouldn't match

harmonic balancer timing marks / tabs shouldn't match

09-17-2014, 08:14 AM
Scott if they were stern drive engs matted with trs drives and trans there both lefty's

joseph m. hahnl
09-17-2014, 09:52 PM
Firing order on the cap. On inboards with Velvet drives The starter is usually bolted on backwards "aft of the engine". I do not believe that there has ever been a reverse rotation Stern drive. But the firing order is truly the best way to tell. Or jump the starter and see which way it cranks:biggrin.:

09-18-2014, 07:18 AM
Remove the timing cover and look for a gear drive w/an idler to reverse cam rotation.

Scott Pearson
09-18-2014, 07:33 AM
Thanks for the great info guys. I missed out on these engines...I need to start looking again for a BBC. This guy had 2 and I figured I would buy both.