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Adjusting Gear Shift Linkage

Category: Engine

Contributed by Chris Woodbury

Summary: One more task that might come up a bit more often is the adjustment of the gear shift exchange mechanism and throttle control.
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The Morse MT-3 single lever dual control unit and the Volvo Penta DS unit connected by Morse control cables comprise the system that does the job. These devices switch the transmission from neutral to reverse or forward given input from either Morse control. It is quite clever and very simple but needs lubrication and checking from time to time to keep it smooth.

The DS unit is an 'or' gate type cam-operated device, which pulls or pushes the transmission shift lever to its detented positions, through a single sheathed control cable, no matter which control station gives the input. The Morse control is a more complicated contrivance which coordinates the shift requirements with the throttle control. It does this with well designed accuracy using cams, levers and clutches to translate lever position to the two control cables. All this happens in a beautifully coordinated way when properly adjusted. If not, the transmission could be damaged through slippage or you could have lousy coordination between control stations. This happened to us during a storm one time when we could not get into gear with the inside control, because the other control was misadjusted.

To check the adjustment put both Morse controls in neutral and (engine off), disconnect the control cable at the transmission shift lever. Clean and lubricate the lever detente ball with WD40 and shift it back and forth to get an idea of how far it travels. Reconnect the control cable and have someone work the Morse lever to forward and reverse. Watch to see that the shift level goes all the way to the detente positions. Watch the DS unit (not so easy on some boats) and lubricate the contact areas with a good light marine grease. With both controls in neutral the DS unit control rollers should be positioned just over their cam valleys and the roller bar (A)

gear diagram

As one lever is pulled, the roller for that cable jumps up on the cam while the other roller falls into its valley. On further deflection the output bar (B) operates the transmission lever through another control cable. The first 30 degrees of Morse lever rotation should put the transmission in gear; by then the pre adjustment is used up and the throttle runs up throughout the remaining deflection.

The Morse controls have friction clutches to help them hold position. This too might need adjustment, but it is quite involved. Friction build up in the control cables can interfere with the operation and can only be checked by disconnecting them at each end to find which one is stiff. A real overhaul includes removing these cables and disassembling them for lubrication. If saltwater has penetrated any of them, a new Morse cable assembly is the only fix, because rusted cables can not be lubricated satisfactorily. Normally everything should be fine,but when I checked ours I found the forward shift stopped short of its proper position; which explains why the transmission gave a kind of delayed clunk when going forward. If something like this is going on, make the adjustment soon, but if not leave it be. I have factory info on all this. If anyone wants a copy, request it through this website's contact form.

See an enlarged diagram: here

From May 1999: WARNING, as we said in previous issues, if your Morse-DS unit controls are not putting the transmission fully into gear (forward most importantly) you should take steps to correct this immediately. Incomplete forward selection will cause the boat to delay and then clunk as she begins to go forward. This will result in damage to the clutches and cost tons to get fixed, maybe, if you are away from the home yard. Fortunately, the Velvet Drive Transmission is a very common unit and is still in production but you don't need problems like this on your dream cruise. A repair job for this could be $600 about 1/3 the cost of a rebuilt unit.