mating season

[flyboyo2]

How, in the name of all that's making me crazier, do I mate the shift shafts on a '89 Mariner 75 hp?  Dropped the L/U for a pressure test and now after multiple attemps to mate the upper shift shaft into the lower reverse lockout cam it's a no go. I've connected them twice and all I had was FWD.  Google search has been no help.  Would a bigger hammer help? The virtually worthless Seloc manual recommends hitting the shaft with a punch...WTH?

[Capt. Bob]

Not sure this is what the problem is or if it will help.

Re: Trouble with lower unit 75 horse Mariner

The book says otherwise, but big guns on here, and this little pee wee, like to set the shifter in the lower unit to F where prop ratchets in the free flow direction but offers resistance when turned in the direction that the prop turns to move the boat forward. Then set the shift lever on the Remote control to F. The reason for this is in the next paragraph and if you were using N, you couldn't do the alignment....would have to turn the crankshaft which is much more awkward than turning the prop in F gear.

Assemble your lower unit and when you get to the last inch, the splines of the shifter should match and with your hand on the prop, rotate it until the drive shaft splines line up and the LU fully mates to the mid section......be sure that your water tube is in the bottom of the powerhead.

Then, with the two sections fully meshed place the shift selector in N and ensure that the prop rotates freely in both directions and then while slowly rotating the prop and slowly moving the shifter into R, the gears mesh and the prop offers resistance to turning in BOTH directions. (Reverse gearing is composed of square gears that have to line up before the shift can occur....unlike F which aligns itself. If you force it you will damage your shift linkage.) Then button her up...


In any case, Fitz will be along soon to help.

Good luck.

[fitz73222]

If you have a 1989 Mariner 75 with power trim, there is no reverse lock cam, that's  pre 88 in line stuff with no power trim that has the shift cam. take the cowling off of the motor, shift the control box into Neutral and the gearcase in neutral by rotating the shiftshaft spline counterclockwise from its forward position to the neutral detent. Slide the gearcase into the midsection, water tube first, then shiftshaft connection, then driveshaft to crankshaft while rocking the flywheel back and forth to get the spline to go in. Done.

[Capt. Bob]

See, I told ya he'd show up.

Fitz, is that anything similar (your method) to what I copied and pasted from another Forum?

[fitz73222]

See, I told ya he'd show up.

Fitz, is that anything similar (your method) to what I copied and pasted from another Forum?

Not really, everyone wants to do it differently. I just do it my way that seems to work well and has stood the test of time. Some older Mercs are a royal PITA. But the '89 and up, 75-125 hp loopers are very easy, I'm surprised flyboy is having issues.

[flyboyo2]

Flyboyo2 is not surprised that Flyboyo2 is having problems, I live my life following O'toole's Corollary to Murphey's Law, to wit, Murphy was an optomist.
I should have asked you guys for help yesterday and saved myself a lot of frustration. I think the lower unit on this motor is a replacement from a manual tilt motor. Instead of having a shift shaft adapter it has a reverse lock cam. It also has the hole where the locking rod used to be. I used more than my allotment of industrial strenght invective trying to make something work that was not even installed. 
Now all I have to do is figure out if the grinding sound with accompaning rough vibes are normal when rotating the prop shaft CW in FWD gear. 

[fitz73222]

Flyboy,
I've never seen a shift cam on any larger Merc made after '87, well if it has one, it slides over the lower shift shaft on the gearcase and pushes up on a rod the pushes the "claws" down over the tilt pin and keeps the engine from tilting in reverse when you give it throttle. This also applied to neutral. You had to put the engine in forward gear to release the tilt lock, but that was old school Mercs up to 87. So you have a 3 cylinder 75 or a 4 cylinder 75? If it's 4 cylinder, it's older than 89'. A picture of this motor would be worth a thousand words. if you have a grinding noise when you turn the prop, it's off a tooth on the shift spline and it's not completely in neutral or not completely in gear.

[fitz73222]

Actually, lets get the terminology correct. There is a shift cam down inside the gearcase the pushes against a pin in the hollow end of the propshaft that pushes against a spring that pushes against a cross pin in the clutch dog that shifts the engine in and out of gear. The reverse lock cam is the device I referred to that is used for keeping the engine from tilting up when you throttle up in reverse on engines with manual tilt. Now one thing you never want to do is shift any Merc into reverse without either spinning the propeller in either direction or the engine actually running to help the clutch dog "find" the correct mesh into the reverse gear since it is mechanical engagement. Forward doesn't matter. It's spring loaded and finds the mesh as soon as you shift and won't hurt anything if you don't spin the prop or have the engine running. Forcing the engine in reverse without spinning the prop or engine running can damage the shift cam in the gearcase which requires complete teardown of gearcase to replace the cam. My advice is find someone to work on this for you. I know it's temping to do this yourself but some of this stuff takes some experience to do correctly without breaking something.

[flyboyo2]

It's definately a '89 3 banger, serial # is 205443. The reverse lock cam fits over the lower shift shaft and had me totally confused because there is no rod for the cam to push against. The hole for the rod is in the gear case directly in front of  where the shift shaft comes through.  I need to find a plug for it.  This is my first rodeo riding an outboard so I'm way behind the power curve on these things.  I was unaware that the PTT was the reverse lock.
I will resume my attack tomorrow using your advice for mating the shafts. My attempts so far resulted in not being able to get the upper shaft to mate with the opening in the reverse cam due to me trying to position the cam correctly.  That was a real PIA.

Thanks again for your sage advice.  I'll get a pix tomorrow.

[flyboyo2]

I think I've had the shnitzel...I just read your last reply and  have put it in and out of reverse several times without the prop spinning.  The grinding noise and rough turning is probably the cam you refered to.  See I told you Murphy was an optimist.