Hello out there...I'm a modelboater from the netherlands and have a question about a .45 OPS engine.I want to know if it's possible to change the direction it's rotating in.That's because I want to build two of those engines in my M-1 Supercat (1.40 m ,surface drives) and therefor need one of them to rotate cw and one ccw.Has anybody got advice on this subject?

Are you dealing with a front intake or rear intake OPS? The front intake will require a new crankshaft with the porting changed for reverse rotation. Although I seem to recall that on the K&B 3.5 with the removable crankshaft housing, it was possible to rotate the front housing 90 degrees to get reverse rotation. I think that was done for the outboard version. Does you OPS have a removable front housing? On the rear intake, the rotor will have to be timed for reverse rotation or you might be able to rotate the rotor housing to affect the timing. I can't tell you if either the crankshaft or the rotor are available for reverse rotation. I'll take a guess and say that the parts will have to be custom made.

Thanks for the quick reply!!! I'm not exactly sure what you meant with front and rear,so I'll try to explain....the crankshaft with flywheel are on the same side as the exhaust.The intake/carb are on the opposite side of the exhaust.So I guess that means it's a rear intake as I would call the crankshaft-side the front....right?

Hopefully someone that's real familiar with the OPS engine will check in. I believe it is as simple as rotating the back plate to a new position to get the reverse rotation but you will have to be carefull that you don't create an interference for the liner or piston when the back plate is rotated. You do have what we term a rear rotor engine.

Bring the piston up to the top of the stroke for reference, and leave it.

Remove the backplate without loosing its rotor orientation to the crankpin. Be careful and look for where the opening is, because just the slightest bump and gravity will make it turn. Take note of its position, or what rotor slot it was originally in.

There are two slots in the rotor disk, one each side of the brass axle pin.

Rotate the disk 180 degrees and re-insert the backplate, being careful the crankpin returns INSIDE the slot.

Looking from the rear view of the motor, the carb opening has to be turned 90 degrees to the right.

The rotor timing will still be off slightly, but the engine will work in the opposite direction.

That should do it.

If you loose reference between the drum rotor and the crankpin, start over with the carb mount towards the top, and the piston on its way up, and the rotor just begining to open.

Thanks Jetpack. I had OPS's many years ago and I knew the back plate could be rotated but I wasn't sure the rotor had two crank pin holes. Depending on the intended use of the boat, the minor loss of power shouldn't be an issue. Hondabc73 comes across as a newcomer to boating.

No problem, those OPS's are nice strong runners...I just wish they still made them. Sad to see them fall away like they did. Nice simple design and strongly built.

Well John , you were right about the fact that I am a newcomer in the world of nitro boating.....Before I was more into static models and nitro cars.So what gave me away as a newcomer? HAHAHAHA!!!!!!

Thanks anyway for all the replies,

Patrick

Patrick, you gave it away when you were asking questions about my terminology about front and rear rotor engines. But don't let that be a concern. We were all new to model boating at one time. I'm still learning but have 35+ years in the R/C Boat hobby.