Gearbox dramas... 125hp 1984 Chrysler

[Steven Bates]

Hi guys, recently fitted the ol 125 to our boat, and howl!!! It was going beautifully- motor still is very pleased. Was engaging the gear at low revs very smoothly. Now no. Motor just revs and box makes a sound like teeth chattering? Now it just won't go into gear... Shift rod bouncing around and won't engage properly~ will lock into gear when in shed and turned off, but on water and motor running just chatters... I took the forward controls off, disconnected the throttle and tried to just engage gears- no good! Is this a adjustment issue or maybe something internal in box? I changed box oil, seemed to be no metal in old oil... Was a bit discoloured... I also tried to adjust rod length using nuts on top. I Am out of ideas~ surely there's a fix or do you think box must come apart? (boat was towed over some ridiculous corrugated roads last trip...). Any thoughts appreciated... And may help me stay sane cheers guys~ Aussie Steve

 

[Frank Acampora]

Re: Gearbox dramas... 125hp 1984 Chrysler



First, disconnect the coupler under the transom clamps and push down on the shift rod. This will tell you if the forward gears are engaging inside the gearbox. Unfortunately, it will not tell you if they will stay locked under power.

If the drive dogs are chattering and not engaging at all with the engine running, then there is binding or maladjustment somewhere. Now: By 1984 the engines should have had Prestolite ignition. However, if you have the year wrong and the engine has a distributor, then check drive belt tension. Too tight will cause gear engagenent problems.

USUALLY, the lower unit will lock into gear with the engine off. This will not show much. If the drive dogs are worn, then under power they will ride over each other and not lock up.So it just may be time to open the lower unit and inspect them.

 

[Steven Bates]

Re: Gearbox dramas... 125hp 1984 Chrysler

Thanks again mate... Will try it. Should I try to start motor and engage gears without shift rod attached? And if that's no good is there a link to a diagram of gearbox? I'm pretty handy with the tools I couldn't find instructions on how the box dismantles- only the bit on using string to hold yoke on while installing... Any further hints/ tips are most valued

 

[Steven Bates]

Re: Gearbox dramas... 125hp 1984 Chrysler

Oh yeah~ motor is a 82 model... I keep confusing it with my merc! Has a dizzy, I read post about adjustment of belt and it seems within specs.

 

[Steven Bates]

Re: Gearbox dramas... 125hp 1984 Chrysler

After disconnecting the shift rod, it locks into reverse fully, but in forward it locks prop up if you spin it in drive direction~ but if I spin prop backwards it jumps... Does that say anything?

 

[Frank Acampora]

Re: Gearbox dramas... 125hp 1984 Chrysler

Look at the photos I included again! See the ramp on the drive dogs? These make it easier for the gears to engage. Because of these ramps and especially if the shift linkage is out of adjustment, if you put the engine in gear and turn the prop the correct direction, the drive dog ramps will ride over each other and drop back down with a click. When turned in the opposite direction, they will lock up.

While this sounds contrary, remember that the drive dog clutch is DRIVEN by the gear. When you turn the prop, the chutch is trying to drive the gear THUS, the drive dogs are engaged on their rear surfaces when you turn the prop.

To adjust, you adjust the linkage so that it is LONGER until it no longer clicks when you turn the prop while in forward. NOW, check that the lower unit will still go into neutral and reverse. Since there is some clearance between the drive dogs when engaged, you can move the prop a bit . If you have too much throw on the linkage, you can actuslly feel the drag as the drive dogs slide on the surface of the gear. Too much throw will wear the brass saddle so it is not preferable. The ideal is the have the drive dogs fully engaged yet no undue pressure is exerted on the internal parts. Since down is forward, to give more forward throw, the nuts under the carb must both be adjusted UP, thereby making the linkage longer. Go slowly, about 1/2 to 1 turn at at time. It is very easy to put in too much adjustment.

 

[Steven Bates]

Re: Gearbox dramas... 125hp 1984 Chrysler

So it sounds more like an adjustment issue? I hope so... Is there any reason it has happened? Vibrations or the like? Like, it was going sweetly, then just decided to play up..? I'm gunna adjust the rod till both forward and reverse click in nicely~ in hindsight I probably shouldn't have played with shift rod nuts so I had a better starting point. If this has no result, I spose id better go into box for a squizz... Or go beg my crappy local boat stores to look at it, straight after I apologise for not owning a Lewis or maxim boat and daring to bring the big ol beast to their shop... Haha