help on reverse lock cam

richierichie

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Mar 5, 2006
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i just replaced water pump impeller on my 76 model 402/ 40 hp mercury. i have a manuel that says for older models you line diagnol to the mount screws. on the newer model it says to align high part of cam to middle nut on lu. right now i am stck in foward gear when i crank up with my shifter still in neutral. please help :eek:
 

papasmurf

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Nov 9, 2004
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181
Re: help on reverse lock cam

The easiest way I found is to place both the shifter and the lower unit in neutral. Turn the flywheel by hand to line up the splines of the driveshaft and then line up the upper and lower shiftshafts.
 

richierichie

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Mar 5, 2006
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Re: help on reverse lock cam

i had stator, rectifier, and solenoid questions and never got a response. i repaired myself by general knowledge. thanks for replying. i have no clue on upper and lower shafts what you are talking about. this i know.with lu off propeller turns freely. there is a small rverse locking cam near the front of the lu. the long shaft only has splines that will slide into engine at flywheel. no other gears are in sight. do i just push shaft up until it aligns into engine if so what direction will the reverse cam aim?
 

MercFan

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Dec 31, 2005
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Re: help on reverse lock cam

The "small reverse locking cam" is your selector shaft. Is gives forward gear aswell. Get is shifted into neutral. Make sure your seletor/throttle on the boat is in neutral aswell.<br /><br />Then simply slide the whole lot together. 3 parst must engage. The drive shaft must connect to the crank shaft (Flywheel). The selector shaft must engage properly in neutral. And the copper water pipe must engage.<br /><br />When you have these 3 engaged, you can check if the selector is working properly. The prop should be in neutral and spin both ways. Then you move your selector/throttle in the boat to reverse. The prop should be locked in both directions. Then move your selector/throttle into forward, your prop should lock in one direction and ratchet in the other.<br /><br />If all is well, continue to pull the LU up with nuts and tighten the nuts in a cross-over pattern.
 

AMD Rules

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Sep 23, 2004
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1,707
Re: help on reverse lock cam

As Mercfan pointed out, you need to make sure your lower unit and your gear selector are both in the same position. Check your prop behavior as he pointed out, and position your selector accordingly.<br /><br />The 'reverse lock cam' is a ramped cam that engages a locking mechanism on your mid-section that prevents the lower unit and prop from climbing upwards when you are in reverse. It is basically a safety device. When in forward motion, the cam lock is disengaged to allow the motor to swing up in the event you hit a submerged object.<br /><br />The position of the cam on the splined shift shaft is important. You may be able to install it in a variety of orientations (not keyed?), but only one position will give the desired locking feature when the shift shaft is in reverse gear.<br /><br />I don't know the answer to ritchie's question. Hopefully someone has a manual handy that describes where the cam should be pointing during assembly (the Clymer manual I have does not). It will also relate to the position of the shaft shaft (neutral/reverse/forward) during installation.<br /><br />The high point of the cam needs to be positioned directly under the push rod that engages the locking mechanism, when the shift shaft is in reverse.
 

richierichie

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Mar 5, 2006
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Re: help on reverse lock cam

thanks guy. i came home today and got it working. does reverse gear always sound a little noisy when engaging.
 

rickdb1boat

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Jan 23, 2002
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11,195
Re: help on reverse lock cam

It always did on my 67' Merc. 650....Shift firmly into gear...
 

richierichie

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Mar 5, 2006
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Re: help on reverse lock cam

i took my boat out today for the 1st time since i replaced impellor and got boat running from purchase. the boat went into gear in the right direction each way. 2 questions. when i put in reverse the engine kicks up out of the water. the second thing is when i get to half throttle after plaining out the engine revs and it fills like i am hitting air pockets of water or something. i noticed a rattling noise at a bar wear the engine sits against at the transome. the engine has a bracket that has slots that looks like it shold go over the bar with the pin in it. when i tilt the motor up this bracket does not move but has a rod that goes down to the foot. is something maybe binding this mechanism? please help
 

rickdb1boat

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Jan 23, 2002
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11,195
Re: help on reverse lock cam

Place shifter into forward. This should raise the locking mechanism that grabs the pin. Tilt the motor up and then lower it again. Then, when you shift back to neutral or reverse, the "Teeth" should grab the pin(What you are calling the "Bar"). This prevents the lower unit from kicking up in reverse. What I'm saying is, you cannot have the motor tilted and the shift lever in neutral and just lower the motor and go. It must be in forward when you lower the motor. The reason you are hearing a rattling, is that the lower unit is not sitting against the bar like it should, but is sitting against the reverse locking mechanism(Teeth). This is allowing the pin to vibrate in it's holes and make the noise you are hearing. But nevertheless, you must initially get the lower unit to sit on the bar. If it's not doing this, then the rod that activates the mechanism is installed incorrectly inside the lower unit. One easy way to see if it's working at all, is to raise the motor up and lock it there. Have someone move the control lever from forward to reverse and watch and see if the teeth move. As for the motor reving up when running, it could be that the motor was tilted out too far do to the fact that it was hitting up against the mechanism and not really sitting down on the pin as it should be. Or it could be that you need to change the position of the pin to another hole the will tilt the motor toward the transom further. Check it out and let us know what it looks like.... It's been a long time since I worked on that old motor, so I'm going from memory when I say that you must install the cam inside the lower unit correctly in order for the locking mechanism to function properly. I do not recall the position it needs to be in, but if you take a look at it, you will realize how it must be installed to work. I had the same problem when I bought my motor and finally got it right after a few tries, with no manual...
 

richierichie

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Mar 5, 2006
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Re: help on reverse lock cam

thanks alot rick. i dont know if it was working before i removed the lower unit the 1st time. i took the lower unit down again and no matter what i did with te little cam inside the lu the way it was i could not get the gears and the latch in sink. i took the cam off and turned it around. this is what i have now. in foward gear with motor running the propeller spins clockwise, with motor off and in foward it ratchets clockwise and locks counter clockwise. in neutral it spins freely and in reverse with motor running it spins counter clockwise and ratchets counter clockwise and locks clockwise with the engine off. the latch now slides into the bar when the engine is lowered in neutral. the gears seem to be engaging properly and the motor is coming all the way down as it should. is there anything i am missing? will it unlatch this way if i hit something while moving? i think the high revs at 3/4 speed was the engine raising out of water.
 

rickdb1boat

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Jan 23, 2002
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11,195
Re: help on reverse lock cam

Sounds pretty good. The important thing is, when in forward gear, can you raise the motor up freely? It should not lock in at all in forward. If that's the case, you're good to go....And make sure the motor is trimmed correctly to avoid the prop blowout you were having.
 

richierichie

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Mar 5, 2006
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Re: help on reverse lock cam

when i took this boat out the 1st time it crancked in about 20 seconds only by using the cold start lever. i ran the boat upo and down the lake for about 25-30 min.i then cut it off for about 10 min. to try out the trolling motor. when i went to crank it back up it kind of spit back a few times and i ended up using the electric choke and then it started back up. is this normal or should it crank back the 1st time you bump the starter? thanks
 

rickdb1boat

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Jan 23, 2002
Messages
11,195
Re: help on reverse lock cam

Depends on the temps. If it was fairly cold outside, probably need to choke it. Also, those are pretty cold blooded motors to start with, so it's not to unusual to have to give it a little choke to get her going again...
 
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