msel9669

Is it possible to change the rotation of a 5.7 merc? Has anyone pulled it off? I have come into one that if I can change the rotation I can use it to replace a missing motor in my CC Stinger. I have heard rumors that it can be done but you have to relace the pistons,rods,cam, & distrib. gear.

knotrated

camshaft and distributor gear

msel9669

Is that all there is to it??

tbanzer1

Chris Craft had a reverse rotation 350 (volvo). They used a camshaft with a gear to gear drive vs a timing chain, this way the oil pump still turned the proper direction. They also used a special rear main seal. If you look closely at a rear main seal there are small grooves that direct the oil back towards the center of the engine when it rotates.If the incorrect seal is installed the oil that gets past the lip seal will be pushed out. Strangest Small block I ever saw. The motor was installed backwards in the boat and drove the outdrive off the front of the crank.

BillK

ms,
That is all there is mostly. To really do it correctly, you should also swap the pistons from one side of the block to the other. The reverse rotation engines had them in "backwards" compared to the "normal" rotation engines. You could probably leave them like they are but you might get some piston slap noise due to the offset wrist pins.

The other problem you are going to run into is the rear main and timing cover seals. The seals need to be the correct ones for a reverse rotation engine. The seals have small grooves on them that help pull the oil back into the engine, and if you use the normal seals on a rev. rot. engine, they will pull all of the oil out and make a pretty good mess.

You will need to use the reverse rotation starter too. All of the parts are readily available.

Hope this helps,

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Donzi502

I wouldnt even consider to do it without swaping the pistons over, I think you will be looking for trouble if you do.

jeff32

I agree not changing pistons.

Reed Jensen

Besides the pistons... you may have forgotten that the crankshaft is drilled to oil the rod journals prior to compression. What about the cooling system? Are you going to run the sea water pump backwards? Or the main water pump if it is still installed? What about the timing marks on the vibration damper... they will be backward also. What about a supercharger, it would have to be configured to run in reverse too. The main reason engines were modified to run in reverse harkens back to the old days before outdrives that could change the direction of the prop. So... if you were running twin engines and wanted counter rotation props, your only choice was to run the port engine in reverse ( if you wanted your props turning "out").Some people have the idea that both engines turning the same direction "torques" the boat over.... maybe... just a little. But the rotating mass of the crank and flywheel weigh just over one hundred pounds.... is it really going to effect the hull that weighs 100 times that? Some people think so... I don't.....

Reed Jensen

Here is a nice alternative to reverse rotation.... mount two engines tail to tail and have a shaft that goes around the rear engine......

MOP

Dumb ? but I have worked on quite a few twin I/O's have not run onto opposites are you sure yours turn opposite or do you just think so?