It's an adjustment and it's easy to do. I had an A4 in my Pearson Triton. Here's my description of the process from my old website:
Please reference this image for adjustment description below:
The reversing gear on the Atomic 4, what many refer to as the transmission, is easily
adjusted. However, despite the appearance of an easy job, I was intimidated by the
prospect and put it off far too long. The reversing gear is prone to becoming
mal-adjusted over time and can make engaging either gear or staying in gear difficult.
In my case, it was very difficult to engage the forward gear and impossible to fully
engage reverse. It got to the point that I wouldn't take the boat out on breezy days as I
could not rely on motor power for docking.
To remedy that, I read as much as I could on the procedure. It is really very easy. You
will need only a few tools:
Large flathead screwdriver
Gasket (available from Moyer Marine HERE)
Permaflex gasket sealant
Before removing the cover plate, put the motor in neutral. You should be able to rotate
the shaft at the coupling by hand. Once that is done, remove the cover plate.
The plate for the reversing gear cover is held in place with four half inch bolts, which
are easily removed. Once the bolts are removed, the plate slides right off. When the
plate is removed, you should see the assembly in the photo above.
The shaft should be spun so the lockscrew is positioned at the 12 o'clock position and
visible as illustrated in the above photo. The lock screw and the adjusting collar (which
is the gear the lockscrew secures) adjust the forward gear. The reverse adjusting screw
adjusts, you guessed it, the reverse gear.
Adjust the forward gear first. This is adjusted by manipulating the adjusting collar. If the
collar is moved to the right, it will tighten it. So, if your forward gear slips while engaged
- which is common - you would move the collar to the right.
To move the collar, back out the lockscrew until it no longer engages the gear. IT IS
CRITICALLY IMPORTANT THAT YOU DO NOT REMOVE THE LOCKSCREW FULLY.
If it falls into the oil beneath the assembly, you're in for a long afternoon. Once the
lockscrew is backed out, the collar will be able to move by hand. If it sticks a bit at first,
apply steady, controlled pressure. You need to be able to monitor how much you adjust
it. It typically requires only a notch or two to be sufficient.
When the collar is adjusted, simply back the lockscrew back down. It is important to be
sure it fits securely into the teeth of the adjusting collar. Also, do not over-tighten the
The procedure for adjusting the reverse gear is equally straightforward. The gear is
adjusted by a 3/4" inch bolt called the reverse adjusting screw, again see above photo.
If you are slipping in reverse, tighten the bolt; if you cannot engage reverse fully,
loosen the bolt slightly. Do not overtighten the bolt as the retaining plate can break.
Test your adjustments by engaging forward and reverse with your shift lever. The
forward gear should engage firmly after passing through it's detente. The reverse gear
does not have a detente, so just go by feel. You should be able to push your gear shift
fully into the reverse position. If you cannot, then you need to readjust.
After this, simply replace your gasket if needed and reinstall the cover plate.
TIP: You may want to go ahead and change your oil while the cover plate is off. The Atomic 4
is designed so the engine and the reversing gear share the same oil. Simply pump the oil out of
the easily reached bottom of the reversing gear assembly. Not only is this far easier than sucking
it out of the oil level tube, you can usually get more oil as you can reach lower into the assembly
than the oil level tube will