1980's Merc 9.8 wont go into reverse, won't stay when it does.

[lmuss53]

Is there an adjustment somewhere on this linkage? Everything seems to moving where it should, clicks in but won't stay engaged. If you back the gearcase housing nut off 1/2 turn it won't click in at all.

I had it apart and everything looks good, no excessive wear on gears or reverse or forward smaller cogs/gears, pin is clean and not worn, never modified, cross pin is clean no slop in it at all spring is all there and looks fine, shift cam shows signs of shifting but is not worn. The gear is up against the shoulder in the case, the nut is tight but not overtightened. It just seems that when the shift cam pushes the gear back to go into reverse their is not enough travel. I had the lower unit off and the shift cam out, splines seem good, properly lined up and not worn from shifting, no flat spots on the cam or pin.

Someone suggested dropping a small spacer in the pin hole in front of the gear cross pin to move everything that way 1/16 inch?

I don't want to modify anything like that, the thing should work like it was built.

Any advice is greatly appreciated.

SN, is 6476660

 

[racerone]

Have you tried adjusting anything at the top ?----------Look for possible adjustment on shift mechanism up top.

 

[Texasmark]

Any history on the engine?
Visible handling damage?
I agree on racerone's comment.
I agree on not modifying if everything looks good. My first reply was going to be the cogs were worn off but not so.
Only weak link in there would be maybe the spring, but that would have more effect on F where it has to exert adequate pressure when extended max.
How does the shift linkage attach to the shift rod, up at the top, under the powerhead? Is is a spline, 2 flat sides, just compression from an arm with a slot and compression screw...clamp sort of thing. Rod bent?
I had a '75ish 7 ? but don't remember much. Shifter came out the front of the engine under the cowl?????? Wasn't on the side was it? I know back in the 60's I had an OMC with the shift handle on the side and being a portable engine it was prone to damage when laid on that side when transporting.

 

[racerone]

Just look for the adjustment up at the powerhead .---Beside the block on starboard side !

 

[lmuss53]

OK Thanks, I'll check it out, I don't think there is an adjustment though.

The linkage has a gear at the top that turns the shaft. The shaft turns inside a 3 step cam in the front of the gearcase housing,

Step 1 is the lowest, the spring is completely relaxed and the engine is in forward.

Step 2 is the center position and the engine is in neutral, the cam is centered when you look in the gearcase without the prop shaft in the housing, goes in to neutral when running, but occasionally grabs at forward.

Step 3 is the highest step and the engine should get popped into reverse.

The cam is not worn on the lobes, or loose on the shift shaft. The spline has a flat so it can only go in the shift shaft the right way. With the the prop shaft out the shift cam turns so that the pin would have to be on top of the reverse lobe, The pin has no alteration marks on it.

I believe everything on the shaft is in place properly, so the gear is not moving far enough to engage the reverse cogs.

Another thing I noticed is it wants to grab at forward when you shift it into neutral, another indication that the shift gear is not sitting in the center when it is in neutral.

The motor is at camp, so I won't be able to get it apart again until tomorrow.

 

[racerone]

You realy should look at the adjustment beside the engine block !

 

[BLKBEARD]

Check to see that the reverse lock hook is not hitting the tilt angle pin or being interfered with. My 1984 9.8 won't shift into reverse without that pin in place. If the reverse motor locking hook can't pull down the shift lever can't move through the full shifting range. hope this helps.

 

[Texasmark]

Check to see that the reverse lock hook is not hitting the tilt angle pin or being interfered with. My 1984 9.8 won't shift into reverse without that pin in place. If the reverse motor locking hook can't pull down the shift lever can't move through the full shifting range. hope this helps.

You may have nailed it. After what he said problem wasn't in the LU.

 

[lmuss53]

I will check all these thing tomorrow fellas, I really hope you are right.

 

[BLKBEARD]

A quick check is to tilt the motor up into the travel position, & engage the lock leverto hold up the motor. In this position you can look underneath and see the reverse lock assy., & there won't be anything interfering with it. I found this out the hard way when I re-sealed my lower unit. Drove me nuts. I cured the water infiltration, but lost reverse. I repair things for a living and have a factory service manual for this engine, so losing reverse was a blow to my ego and a cause of severe head scratching.............Good luck

 

[lmuss53]

The lever is moving freely all the way toward the rear, just not going in to gear. They are using like it is, so I will not get it until tomorrow now.

I'll let you all know what we find.

Thanks for the replies.

 

[lmuss53]

So today I find out they had it in for a spun prop and the guy there decided to look the prop shaft over while he had it. He turned the LH thread nut the wrong way and overtightened it until it bottomed out.

This motor comes with a set of shims between the reverse gear and the bearing race that space it over to allow the reverse gear to engage. THAT is the adjustment method, kind of like putting a car rear end together. There are no shims between the gear and bearing on this motor, and I had to surmise that the overtightened nut closed some gap that had been between the bearing and gear.. I tapped the gear out of the race about 1/16" and it went into reverse and stayed there. I have to assume that either at the factory or sometime in service someone put this back together and didn't bother with the shims. It worked until someone else overtightened the nut and took all the gap the shims would be providing out of the assembly. I have ordered the shim set and new seals.

My question to the forum now is, does anyone know the proper way to reassemble this to get the appropriate clearances and have it back together right? BLKBEARD any chance you can snap a pic of that page in your manual and post it up? 1984 model 9.8 Merc.

 

[lmuss53]

The missing parts are #58 here, 5 shims from.002 to .010 'merican measurements.

 

[Texasmark]

I don't recollect immediately, but vaguely remember how to test the shim thickness for proper gear engagement.....setup is in the service manual. In there also is the drive shaft pinion to F and R which has to be checked with a special gauge. I understand what you are saying about needing shims and that makes perfect sense. You think PO shade tree mechanicin on outboards is a pain, try it on 50 year old farm equipment, especially tractors. No telling what you'll find.

 

[BLKBEARD]

I'll see if I can do that tomorrow, Also be sure you have both spacers on the prop. I think one is splined and the other is un-splined, one goes in back of the prop, the other between the prop & prop nut. if one is missing, tightening the prop will force the prop shaft & gears out of adjustment. The shims are very thin use a angled probe to feel for them. but make sure the spacers are on the prop first. hope this helps

 

[lmuss53]

OK Guys, thanks, everything is here except the shims. I laid it all out and stepped through it all and that's when I noticed the missing shims. I had not had the gear and bearing off the shaft so I wasn't looking for parts missing there.

I can see someone using the shims out method to let the gear find it's way to it's "happy spot" on that shaft. It would be a quick and dirty way to put the shaft back together without bothering with the shim setting. It worked here for over 20 years until someone turned the LH thread nut the wrong way and pulled all the spacing out of the assembly.

BLKBEARD, if you can find that I'd appreciate it, if not I think I can go to a friend's place and probably find a manual.

 

[BLKBEARD]

Sorry for the delay, My scanning software had to be re-loaded before I could scan the damn pages. Haven't scanned anything in too long I guess.

 

[lmuss53]

BLKBEARD, can you post those page numbers, I have that manual in a cd but it is 700 pages and the index is not here.

 

[BLKBEARD]

6-20, 6-21

 

[lmuss53]

Thanks, I appreciate the help. I'll let you know how it goes.