[Green1]

Installed a new impeller in 1970-71 Mercury 400 40hp 2 stroke 2 cylinder motor. Had the control box in forwards but the reverse cam was moved when I had the lower unit off, I’m not sure how to re-align ? Put it back together with the reverse cam in the middle when in neutral. Now will only idle along in forwards but reverse will run at full speed and throw the motor out of the water. Is there a way of re-aligning the reverse cam and is this the problem ?

[Laddies]

[CharlieB]

As long as it shifts into forward and reverse then you have the shift shaft indexed correctly to the control box.

Your problem with the reverse lock is simply that the cam is indexed incorrectly on the shift shaft.

If you look very closely at the ramp on the cam you should see a contact spot midway up the slope, this is the point of contact with the reverse lock linkage while the control box and shift shaft are in the Neutral position. Rotate the shift shaft to the Neutral position then install the cam with this spot directly facing forward, rotate the shift shaft to Reverse and reinstall the lower unit.

The Reverse lock should be partially engaged while in Neutral, fully engaged when in Reverse and released when in Forward.

[Green1]

Thanks for the quick feedback ! Tried again today but still having difficulty finding neutral on the lower unit. I can turn the shift shaft all the way in one direction (reverse) and it eventually locks into something and the propeller will spin freely when I have it locked but I assume this is reverse (not neutral) since it's as far as it goes in the reverse direction. I can unclick it from this position but the propeller will then click if I spin it (Assume this is drive). If I keep going into the forwards direction it eventually gets to another point of some resitance then a very small click and it keeps going past that. I assume that I need to get this to lock into this reverse position when the control box is moved into reverse ? Is there a simple way to know when I have neutral on the lower unit ?

[Laddies]

The shift shaft turns counterclockwise for fwd gear and the prop shaft locks in counterclockwise movement for fwd gear. there is only a slight detent in fwd and the unit will shift by the detent for foward but will stay in fwd gear. Then move the shift shaft back clockwise and the first detent is neutral the prop turns either direction, continue turning the shift shaft clockwise and you will find quite a lot of pressure then a small detent the prop shaft will lock in the clockwise rotation that is rev. If you continue to the turn the shift shaft the cam on the shift will jump by and you will be back it fwd gear

[Green1]

Maybe it's my gearbox then ? If I turn the shift shaft CW I do get forwards on the prop (prop clicks if I turn it the other way) but when I start moving the shift shaft CCW I go all the way past the detent's and no where along the way does it change the movement of the prop. Prop still move forwards and clicks in reverse. If I turn the shift shaft all the way CCW it eventually clicks (not going any further) and the prop spins freely but this must be a faulse neutral then ? Does this mean I'm up for a gearbox ?

[CharlieB]

The spring on the shift slide is stiff enough that it is often difficult to turn the shift shaft CCW with your fingers. The small click is the neutral detent and the prop freely spins both directions.

This is the point to install the reverse lock cam.

You may even install the whole lower unit while in neutral, the control lever must be in neutral and you will have to reach up and turn the flywheel to align the splines.

ALWAYS ensure that the key is OFF, and it never hurts to pull the spark plug wires off the plugs before turning any motor by hand.

[Green1]

Ok that worked when I put it on in Neutral and the prop now spins the right way. Took the boat for a test run and all seems to be working good now. Thanks heaps for the info