Reversed counter roatating lower units...

[Whit]

My stupid mechanic may have inadvertently switched the lower units after replacing the water pumps on my counter rotating suzuki 140's. My question is would this create any problem if the Port lower unit is now on the starboard side and vice versa? Also, if the lower units are on different sides now, should I also reverse the props to the opposite sides?

In the interest in full discosure, the stupid mechanic in this case was me. The water pump project was halted abruptly due to a thunderstorm and in my haste to get everything put away, I didn't lable everything and forgot which lower was which.

 

[Dhadley]

Re: Reversed counter roatating lower units...

You may have done yourself a favor. What type of boat is it? V bottom? Cat? Are the motors mounted to a bracket or are they on the transom?

Regardless of where the cr gearcase is it must have the left hand prop on it. And obviously vise-versa.

 

[Whit]

Re: Reversed counter roatating lower units...

Thanks for the reply. I'm not sure I understand what you are saying that I might have done myself a favor? The boat is a 25 dusky center console- V bottom. So I guess my question is does the counter roatation happen in the lower unit or is it the engine?

The trouble is I know what side each prop came off to but am not 100% sure if I have the lowers on the wrong side or not. Does it matter that the lowers were reversed if the props go back on the same side?

What has me thinking I have the lowers on differnt sides is the trim tab zincs which I kept next to the port and starbord props. One of the tabs is a zinc and the other is just a plastic trim tab. I marked them before I took them off so i could put them back at the same angle. When I put the tabs back on, they didnt line up with the marks unless I reversed the plastic and the zinc one (they both sit slightly differently) which got me thinking I put the lowers on the wrong sides. So if the lowers are on opposite side than before will that reverse the counter roatation or can I just put the props on the way they were and be OK? Thanks

 

[dlkiller]

Re: Reversed counter roatating lower units...

I think he's saying it might work better this way, I don't know why.

The engines and upper driveshafts turn the same way whether it's a standard or reverse rotation, the CR is changed in the lower unit. You need to make sure the CR prop goes back on the CR lower, or your F will be reverse and your R will be your new forward.

 

[MikDee]

Re: Reversed counter roatating lower units...

It's true both motors themselves will turn the same way when running, usually clockwise when looking at the flywheel from the top when running.
Counter rotation is done at the lower unit. You will have different effects depending on which side the counter rotating motor is on. Looking at it from behind the boat, The C.R. motor being on the right, will tend to lift the transom between the props, The C.R. motor being on the left will tend to push down on the transom between the props, it all depends on what works best for you.

 

[Dhadley]

Re: Reversed counter roatating lower units...

Exactly. We find that on V bottoms it may or may not make a difference if the motors are mounted to the transom. If they're on a bracket (or the boat has a stepped or notched transom) it usually helps a little on the top end, some in the cruise range.

Most cr gearcases have some sort of identifying mark on the end of the propshaft. The prop direction can be identified by looking at them. A right hand prop will have the trailing edge (thicker edge with the cup in it) at the top when the blade is in the 3 o'clock position when behind the prop looking forward. A left hand prop will have the trailing edge at the top in the 9 o"clock position.

Don't forget to check / reset the toe in too.

 

[Whit]

Re: Reversed counter roatating lower units...

Thanks all! Very helpful feedback

 

[Randybeall]

Re: Reversed counter roatating lower units...

Take the top cover off the engine, pull off the spark plug wires, put the shift in forward and turn the flywheel in the direction of normal rotation. If the prop turns as it should you don't have a problem, if it turns reverse, swap props from one engine to the othe.

 

[Frank Acampora]

Re: Reversed counter roatating lower units...

Uhhhh! Life 'aint always simple! Not to be the messenger of doom, but some counter-rotating engine pairs were designed with the engines themselves turning in opposite directions and gear teeth cut opposite. If you switch lower units on these engines, you will improperly load the gear teeth on the wrong faces while running--even if you switch props. This WILL cause shortened service life.

Do yourself a favor: With the hoods off, crank over both engines and see what direction they turn. If they do indeed turn in opposite directions, be certain that the correct lower unit is installed on each engine.

 

[Randybeall]

Re: Reversed counter roatating lower units...

Perhaps life is simpler than we care to make it sometimes. On most flywheels there is an arrow marking direction of rotation, I know some people would not look at it but I give Whit the benifit of the doubt. He did come to Iboats forum didn't he? If the engine is turned that direction and the gear selection is in forward you should be able to match prop to output shaft. It would be extremely rare to find the reverse rotation engines in more common boats. I have not searched the Suzuki web site but will do that since you bring up the possibility. Happy boating.

 

[Dhadley]

Re: Reversed counter roatating lower units...

I really doubt that anybody today makes a powerhead that turns backwards. Especially a 4 stroke (and I'm assuming the Suzys are 4 stroke) and really especially if anyone was paying attention when Second Effort went thru the backwards OMC powerhead fiasco. It's realitively easy to run a standard 2 stroke backwards but a backwards 4 stroke is a lot more involved.

Assuming the powerheads are both the same rotation and assuming the propshafts are not marked (so we can tell by looking), all we have to do is put the props on. Pick a prop and pick a gearcase. Once installed start the motor and shift both into forward (or just one). If it / they push the boat forward, the props are on the right gearcases. If pushing the control forward now put the boat in reverse, the props are on the wrong gearcases.

In the off chance the powerheads do turn opposite, I'd bet one of the impellers is installed rotated in the wrong direction.

I'd bet that everything is fine and Whit has been out enjoying his boat.