Need Help

[nate2800]

I have a 90 hp 1986 mercury engine and am having problems with my reverse.The cam that moves the shaft back and forth from forward to reverse is giving me fits. Ive replaced it three time and am going to have to replace it again.For some reason it is chipping on the side and wont fully engage it in reverse . I have no idea why. I really would appreciate some advice


Thanks and God bless
Nathen

 

[Chris1956]

Re: Need Help

Nate, When you say "the cam" do you mean the shift cam located in the front of the gearcase? If so, the garcase has some crucial shimming requirements to make sure the gears engage properly. Did you follow these specs?

 

[nate2800]

Re: Need Help

I am not aware of the shimming would you now how i get these specs,and yes that is the cam i am talking about.

 

[Laddies]

Re: Need Help

The shiming Chris is talking about is the shiming of the carrier depth or rev. gear backlash if there is to much backlash caused by the carrier not being in far enough in the cam and pin cannot push the clutchdog far enough into rev. gear to keep the clutchdog fully engaged

 

[nate2800]

Re: Need Help

so what is chipping the cam?
and do you now where i can get a display so i can see what your calling shimming?

 

[nate2800]

Re: Need Help

Im alot better with pics.

 

[nate2800]

Re: Need Help

Ive got a pic of the cam but i cant figure out how to put it on this thread

 

[Laddies]

Re: Need Help

Nate, goto the non boating technical topics of this site and the first item tell you how to post photos and things

 

[nate2800]

Re: Need Help

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[nate2800]

Re: Need Help

bump for more help

 

[Laddies]

Re: Need Help

Nate,this is not much help I know but in 40+ years I have never ran into anything like that, my only advi to you is to check with a dealer and ask for the Mercury Marine customer service center at either distributer or factory level and get with them for a answer

 

[nate2800]

Re: Need Help

thanks laddies

 

[CharlieB]

Re: Need Help

What is the condition of the shift pin/plunger in the end of the propshaft look like?

If that pin is worn, the contact area can get off-center of the shift cam.

 

[nate2800]

Re: Need Help

the endof it is new the last time i put one of the cams in it i lost one of the ball bearings and the only way to get it is to buy the pin,and the three ball bearings

 

[CharlieB]

Re: Need Help

Hopefully it's a safe assumption that you are installing the pin with the pointy end against the cam.

Strip that propshaft down to bare bones and check it for straightness, if the shaft is bent/warped even slightly it will waiver the pointed end of the pin against the cam.

Check the shiftshaft that fits into the cam, if that shaft is bend/warped the cam does not rotate flatly but moves (?) how to describe (?) (?)

the shift pin would not stay centered on the cam as the cam rotates, but would move off-center, near an edge.

 

[nate2800]

Re: Need Help

O.K. the shifting shaft is bent very, very littleand i do mean very little.
on stripping the prop shaft down is there any thing i need to now, all i have ever done is replace the water pump and this shifting cam,ive never realy messed with taking this apart.

 

[nate2800]

Re: Need Help

bump

 

[CharlieB]

Re: Need Help

http://www.crowleymarine.com/mercury_parts/278/23.cfm

Link above should be the parts diagram for your unit

You should see how the spiral lock wire retains the cross-pin in the shift slider

You will need the shift pin and balls installed and press it all against the bench to compree the spring while you drive out the crosspin.

Once the shaft is bare roll it across a flat surface to check for straighness.

Same with the shift shaft.

Any bend should NOT be there, the bend in your shift shaft contributes to the shift cam being (?) out of alignment with the shift pin.

You might consider inking the cam with a felt pen, install the cam, then install the assembled propshaft and carrier minus the carrier outer seal, shift a couple of times so that the shift pin makes a mark on the inked cam. Tear it all apart again and look at the line made in the inked cam. It should be straight and true, if not then replace the vertical shift shaft.

At some point in time, some was reinstalling the LU and jammed the verticle shift shaft, causing it to bend.

 

[nate2800]

Re: Need Help

O.K. the prop shaft looks good the shifting shaft has a very little bend in it.very little.

 

[CharlieB]

Re: Need Help

NO amount of bend is allowed.

Imagine the contact line through the very center of the cam. at least that's where it is supposed to contact IF/WHEN the shift shaft is perfectly straight. The shift shaft rotates the cam one a perfect horizontal plane, pushing the slider into reverse or allowoing the spring to push the slider out and into forward gear. And boating is GOOD.


If the shift shaft in the lower is not correctly aligned AND timed with the UPPER shift shaft THEN as the cases come together the shafts collide, bolts are tightened crushing the shafts together forcing one or both to bend, when the lower shaft has ANY bend, especially bear the bottom (cam) end, then that cam is no longer on a horizontal plane and the shift pin is OFF CENTER.

Does this make it all clear as mud?