Mercury 500 gear problem

[oba97]

I have a 1975 merc 500 that with the lower unit removed I can be in neutral (spins freely both ways) with a wrench turn the shift rod clockwise engaging forward (ratchets clockwise locks counterclockwise) if I turn it back counterclockwise it will go back into reverse. If I turn it counterclockwise again it will go into reverse (prop locks in both directions). Everything seems to be working good. When I reattach the lower unit I can shift from neutral to forward back to neutral but I cannot get it to go into reverse! It feels like there is a lot of resistance and it kind of springs back. I do not have the control cables hooked up while I am trying this. Any help would be awesome.

 

[GA_Boater]

Normal - Turn the prop/prop shaft when trying to shift into reverse when the motor is not running.

 

[oba97]

Do you mean the actual prop or the flywheel?

 

[racerone]

Prop must be turned when motor is NOT running.----Do not try and shift to reverse with motor either not running or propshaft not turning.

 

[GA_Boater]

Turning the flywheel will work, too. The reason is reverse is only a gear and without the driveshaft or the prop being turned, the gears don't mesh. Forward has a dog clutch which will turn to allow gears to mesh without rotating shafts.

The clutch is why the prop clicks in one direction when in forward and the lack of a reverse clutch is why the prop is locked in reverse.

 

[oba97]

Still cannot get it???? When I push the slide mechanism I get resistance (while turning the prop) and never goes into reverse. It's almost like it needs to have another 1/2" travel to get it into gear. It's aggravating because on my work bench I can get all 3 gears easy, it only a issue when I connect the lower unit to the power head. I have been monkeying with this ever since I changed the water impeller and got things out of wack.

 

[GA_Boater]

Drop the lower unit, hook up the shift cable and put it into neutral, both the shifter and lower unit. Then reinstall the lower unit.

 

[racerone]

???----No the clutch dog is spring loaded.---If you shift to forward with motor not running nothing is being forced by the shift cable and no damage will occur.

 

[GA_Boater]

???----No the clutch dog is spring loaded.---If you shift to forward with motor not running nothing is being forced by the shift cable and no damage will occur.

Who are you talking to? Spring loaded?

 

[Chinewalker]

Is the reverse locking cam aligned correctly? That's the sloped part that sits on top of the shift shaft. Also, make sure the reverse locking mechanism isn't jammed on the tilt pin. If the reverse lock hooks or linkage aren't able to move freely, they'll jam up the shift rod via that sloped cam.

 

[oba97]

I'll fiddle around with it today. When it's in neutral the hooks are locked into the tilt pin. When I pit it back into forward it releases.

 

[oba97]

I'm about to put my head through a wall! I sill cannot get it. I even tried taking out the reverse lock and it still won't work. It like I don't have enough room on the slide bar to get it into reverse.?????

 

[oba97]

I'm not using the controls because I have them apart waiting for new cables, but it should be able to go into gear just by moving the slide bar right?

 

[oba97]

After a lot more monkeying around with it I decided to connect the one good control cable that I have from the control box to the motor. I hooked up the muffs and gave it a shot. I was able to shift from neutral to forward, back to neutral and into reverse. I didn't have the throttle cable hooked up so I only ran i idle speeds but it seemed to work. The prop spun clockwise in forward and counterclockwise in reverse. What I cant figure out is why when I didn't have the control cable connected I could get it into a solid forward but when I put it in reverse I would have to keep pressure on the slide otherwise is would go back into neutral? Does the control box actually hold the motor in reverse vrs selecting a reverse gear?

 

[GA_Boater]

What is happening is when shifting into reverse the gear teeth are hitting the high points of the drive gear and the reverse gear. When shifting with the motor off, something needs to turn to get off the high points of the gears - The reason for saying to turn the prop.

The control box does not hold the lower in reverse. For a simple explanation, it's held by over centering the shift cam.

 

[oba97]

Ok. I just found it weird that when turning the prop by hand at the same time as putting the controls into reverse wouldn't work but it seemed to stay in reverse when the motor was running. I guess one more test is to start the motor with the control cable disconnected and see if it shift that way as well.