75hp Lower Unit - confirming reverse gear is engaged

[KEYCHS1720]

Motor: 97, 75hp,2st, 3 cyl, Mercury Serial 0D283222.
Remote Control: Mercury Remote Control 88688A26

I have the lower unit put back together on my truck's tailgate right now, before I bolt it back to the motor I need to confirm the following:

-When I spin the shift shaft CCW through it's detents: F to N (prop spins freely) and then into R (3rd detent) While spinning the driveshaft CW ; will I be able to hear a gear change or will the propeller begin to spin in reverse as it would in the water? I'm able to click into my reverse detent but I' unable to spin the propeller in the proper direction via the driveshaft.

 

[ahicks]

Please consider that the drive shaft, with water pump impeller installed, should be turned in one direction only.

To check for proper shifting, you would want to turn the shift shaft to a point where the prop shaft turns freely. That'll be your neutral. Then, depending on which way you move the shift shaft from that point, the prop should ratchet when turned on one direction or the other either side of neutral.

 

[KEYCHS1720]

Please consider that the drive shaft, with water pump impeller installed, should be turned in one direction only.

To check for proper shifting, you would want to turn the shift shaft to a point where the prop shaft turns freely. That'll be your neutral. Then, depending on which way you move the shift shaft from that point, the prop should ratchet when turned on one direction or the other either side of neutral.

Why would it matter if I spin my driveshaft with a new impeller installed? The paddles flipping on themselves once or twice isn't going to destroy them.

Building upon your answer, I'm aware the prop shaft will spin freely while the shift shaft is in the neutral detent. Per my original question, I need to know if it is possible to engage reverse gear and confirm it is indeed reverse gear and not forward. How do I tell the difference between forward and reverse gear on the lower unit? Which way will the propshaft spin in reverse while I spin the driveshaft CW?

 

[racerone]

No need to argue / slam folks helping you.-----You turn the driveshaft the way the motor runs / turns.----Then observe rotation of prop.----Easy to tell what is forward and reverse.-----To engage reverse the driveshaft or the propshaft must be turning.----Just the way it works.

 

[ahicks]

If you can engage a gear, makes no difference forward or reverse, on either side of neutral, you're good to go. Put the shift shaft in neutral position and reassemble.

You're right on new impeller vanes of course, but you failed to mention they were new, and it's a bad habit to turn them backwards.

If you MUST know what direction the driveshaft turns, look at the motor's flywheel. There's generally an arrow, or look at the way the notch is cut for the emergency start pull rope to engage. You should be able to figure it out from there....

 

[KEYCHS1720]

No need to argue / slam folks helping you.-----You turn the driveshaft the way the motor runs / turns.----Then observe rotation of prop.----Easy to tell what is forward and reverse.-----To engage reverse the driveshaft or the propshaft must be turning.----Just the way it works.

I apologize if my tone was wrong, I have no intentions to bad mouth any advice given! Only trying to be as straight forward as I possibly can be to simplify my question to hopefully simplify the problem I'm having in the field.

You may have confirmed it for me because I'm unable to make my propshaft spin in reverse by spinning the driveshaft CW (direction of arrow on flywheel). Now what......

 

[racerone]

Just take the lower unit apart for inspection.

 

[ahicks]

I apologize if my tone was wrong, I have no intentions to bad mouth any advice given! Only trying to be as straight forward as I possibly can be to simplify my question to hopefully simplify the problem I'm having in the field.

You may have confirmed it for me because I'm unable to make my prop shaft spin in reverse by spinning the driveshaft CW (direction of arrow on flywheel). Now what......

If you answer these questions, I may be able to give you a hand.

You're telling us that when the drive shaft is turned, that no matter where the shift shaft is positioned, the prop shaft turns in the same direction?

You do have neutral, right? Where the prop shaft does not turn when the drive shaft is turned?

If you have a neutral, can you feel the shift shaft pop into small detents on either side of the neutral detent? One of those detents will be your forward gear, the other, reverse.

 

[KEYCHS1720]

If you answer these questions, I may be able to give you a hand.
You're telling us that when the drive shaft is turned, that no matter where the shift shaft is positioned, the prop shaft turns in the same direction?
You do have neutral, right? Where the prop shaft does not turn when the drive shaft is turned?
If you have a neutral, can you feel the shift shaft pop into small detents on either side of the neutral detent? One of those detents will be your forward gear, the other, reverse.

I have taken the lower unit apart previously, everything is appears to be in working order.
I appreciate the effort, answers below to your questions:
-That is correct, except for when I turn the shift shaft into the 2nd detent (neutral).
-Yes, I have neutral.
-I have no problem locating neutral and or popping into either detent on each side of neutral. However, the prop shaft continues to spin the same direction it did regardless of either detent I "pop" into from neutral, is that normal? My brain tells me in reverse the propshaft should spin a different direction than in forward but I've been wrong before.....does that make sense or I'm happy to explain in a different way.

 

[racerone]

This is becoming difficult.----Are you holding the shift rod in the reverse detent ( vicegrip ) while giving the driveshaft a full turn ?

 

[ahicks]

I'm going to go way out on a limb here, and tell you that it's impossible for that prop shaft to turn in the same direction with the shift detent on opposite sides of neutral.

The shift shaft is sliding a clutch dog back and forth between the forward gear and the reverse gear. Neutral is located in the middle, between them. With the shift shaft on one side of neutral, one of those gears WILL be engaged. On the other side of neutral, the OTHER gear will be engaged.

Put the shift shaft in neutral, make sure the shifter is in neutral, and put it back together. I think in this case, it'll be much easier than getting your head wrapped around this. Best of luck...

 

[KEYCHS1720]

This is becoming difficult.----Are you holding the shift rod in the reverse detent ( vicegrip ) while giving the driveshaft a full turn ?

Yes, that is correct. Does it matter if I hold it though? Isn't that the intent of the detent?

 

[KEYCHS1720]

I'm going to go way out on a limb here, and tell you that it's impossible for that prop shaft to turn in the same direction with the shift detent on opposite sides of neutral.

The shift shaft is sliding a clutch dog back and forth between the forward gear and the reverse gear. Neutral is located in the middle, between them. With the shift shaft on one side of neutral, one of those gears WILL be engaged. On the other side of neutral, the OTHER gear will be engaged.

Put the shift shaft in neutral, make sure the shifter is in neutral, and put it back together. I think in this case, it'll be much easier than getting your head wrapped around this. Best of luck...

I would agree with you but at the same time is I don't know for sure. I can't make the propeller spin the opposite direction which is why I'm wondering if my dog clutch isn't moving far enough back to engage the blocks on the reverse gear?

 

[racerone]

??----There is a strong spring in there.-----It will kick it out of reverse in the blink of an eye.-----Hold the shift rod in reverse and test.----This is simpler than you can imagine !

 

[ahicks]

Agreed. The real detent, the one designed to hold it in gear once selected, is up in the powerhead.

 

[racerone]

The control box and cable hold it in reverse.

 

[ahicks]

I can't find anything detailing where the shift cable attaches to the shift linkage in the parts diagrams. Are you saying the cable attaches directly to the end of the link labeled #27 "coupling shift shaft" here?

https://www.boats.net/catalog/mercu...-0b240450-usa-cat-90-13725-3cyl/exhaust-plate

I'm a Honda guy, and pretty familiar with this lower unit as they use them as well. Further I KNOW there's a shift detent used on the Honda's, so it's hard to believe Merc doesn't use one as well. I couldn't find a neutral safety switch either. Do they just use the one located in the control head? What if it's a tiller, or is that switch located inside the tiller somewhere.

Bottom line, I believe there's a shift detent used. I just can't find it, or the detail where the shift cable attaches for whatever reason. -Al

 

[racerone]

Sorry-----You have to look on another parts page to find the " shift slide "----for this motor !!