The proper 'speed' to shift into gear

[thematt]

This is probably an embarrassingly simple question, but here we go: how fast (moving the shifter) should I be shifting from neutral to forward or neutral to reverse?


I have a 2 control system with throttle separate from the shifter.



I have a zf 15 transmission and haven't had any issues but I always get a loud (healthy?) Clunk when going into forward from neutral. I can't help but think I just didn't learn something basic. Reverse is often quieter but still noticeable.


I have a flexofold prop, so perhaps that's part of the reason why forward is louder...


I typically shift at the speed (how fast I move the lever) I would a stick shift car after throttling down and shifting to neutral.



Idle is ~600 rpm. I always use atf, and fluid looks good.



Am I just being overly worried here? The clunk makes me think I should somehow be doing something better.

[Chotu]

I think you are just worrying a little bit too much. They are clunk when you put them in gear. Try going slowly. It’s still clunks. When it’s ready to grab, that’s when it clunks

[rslifkin]

Generally you'll get the least clutch wear (especially on a mechanically shifted trans vs a hydraulic one) if you shift quickly, although the engagement will be less smooth. I tend to shift most boat transmissions like I'm flipping a large light switch. If going between forward and reverse, it's good to pause in neutral for a second.

[Dave_S]

I'm assuming it is a "dog box", if so faster is better but not with great force. You don't want to hear click click clunk - to slow. You want to have the gears trying to engage but without lots of force waiting for when the gears are aligned then you want them to engage as fast as possible so when the load is on the gear faces you have the maximum amount of engagement.

It is intuitive more than anything because it happens in fractions of a second. While it seems/feels/sounds harsh, they are made to take it.

[Rumrace]

3 types of marine clutches I’m familiar with all take different shifts.
The dog clutch wins but would blow up if there was an actual gear shift.
The Dog clutch common in big outboards and stern drives has a kill switch attached to the shifter. It grounds the spark during the shift. Slam it

Dog Clutch. Take it by the leash drag it over the engine grabs it your in gear. Smaller outboards Push and hold shift.

Disc Clutch. Cars motorcycles has disc clutches. Some automatic transmission like the ZF 8 speed have two automatic clutch packs to shift.
Then there’s boat disc clutches. Merc V drive rated up to 1200Hp multiplate monster with 12 double Springs
Then there is a 45hp sailboat with a lawn mower tractor motor with 2 crappy cups or discs. They work with two rough surfaces matting. The harder you hit it the more wear on the plates the longer you linger the more damage you do to the surface.
A firm gentle shift.

As a power boater now sailing I’ve noted many sailors over propping for a half knot. Power boaters don’t over prop it’s a 4400 RPM threshold, unless your running surface props which have massive disc clutches

Folding props misbehaving cause clutch damage also.

[Rumrace]

Sorry I messed up first paragraph referring to the cone clutch as a dog clutch.
Similar but not the same my bad

[Shrew]

I don't think there is an issue going from neutral into either FWD or REV with authority. You certainly don't want to 'pussy foot' about with it.

The far more important question would be.....how long do pause in neutral before going from FWD to REV, or from REV to FWD? This is what will cause problems.

I had my shaft removed about 2 years ago to find the key almost destroyed, the keyway on the shaft and the coupler wallowed out, and to solve the issue a previous owner drilled the shaft and coupler and used studs to hold them together.

Our guess was going straight from REV to FWD (and vice versa) without allowing the prop and shaft rotation to slow or stop in between.

[GordMay]

According to the Operating Manual ZF 15 M, 15 MIV, 10 M, 25 MA, 25 M, 4-1 M, 12 M, 5 M, 30 M, 15 MA:

”... During normal operation, the transmission should only be shifted with the engine at idle speed. Shifting at higher engine speed may lead to
overstress of the friction disks of the coupling and should be avoided in
normal operation.
NOTE:
The transmission may be shifted from forward to reverse in case of emergency, even at high engine speed ...”

➥ https://manualzz.com/doc/o/5g2hp/zf-...f-15-operation

[Shrew]

Originally Posted by GordMay

According to the Operating Manual ZF 15 M, 15 MIV, 10 M, 25 MA, 25 M, 4-1 M, 12 M, 5 M, 30 M, 15 MA:

➥ https://manualzz.com/doc/o/5g2hp/zf-...f-15-operation

Very interesting. I have a ZF30. In my case it wasn't the transmission that appears to have suffered. It was the shaft, key and coupler.

[thematt]

Thanks for all the answers folks! Sounds like the 'clunk' is normal even if loud enough that I feel like it can be heard in the next slip over.


I'll treat the shift lever as a light switch as one commenter pointed out. I can perfectly picture that 'speed'.



I have an old reliable westerbeke w50 and a v drive on either end of the transmission as well.



A few have asked about pausing in neutral. I always give it at least a few seconds there between forward and reverse, if time allows I give it more... because why not?

[capt jgw]

You're right about the pause between fwd and rev. Give everything a chance to stop turning before you make it turn the other way. One boat I had with a little 11hp would actually stall if I went right from fwd to rev. The engine didn't have the hp to reverse everything that quickly. Made for some exciting emergency stop maneuvers.

[P3sailor]

I wouldn't worry about it, my harley does that through all five gears! Now if your in gear, say forward, then switch to reverse without letting the trans/prop slow to a stop that may create some issues. Just a thought.

[Squanderbucks]

You should possibly check another source. Clunks can come from loose coupling and sometimes worn or shot engine mounts.
FYI

[waterman46]

Had the ZF in our boat. They are great gears.
The loud clunk when you shift to forward is a good sound, if that's all you hear (no whining sounds). If you hear it you know you are firmly in gear, the shifter is properly adjusted and the tranny is not going to slip. Ideally you will also hear a nice clunk when you shift to reverse. To me that sound was very comforting.

BTW the ZF (previously Hurth) can be shifted at higher RPM in an emergency, without damage. At least, the old Hurth manual on my boat says so, and I have had a couple occasions to do that in necessity.