1978 Merc 800 Shift Cam

[AugustMoose87]

So last summer, I was having trouble going into reverse, you can get some details HERE

Anyways, I've pulled the lower unit apart, and as WingedWheel suggested, it looks like my shift cam is bad. The rest of the lower unit looks like it has recently been worked on (at least since '78), but the shift cam has a pretty deep groove worn in it, and the shift shaft bushing looks fairly gummed up, so I'm thinking they tried to get in and replace that when they did the rest of it, but couldn't get to it and decided to not fix what wasn't broken.

So, short of the long, I need to replace my shift cam. It seems to me that once I get the correct tool (on its way), I should be able to remove the shift shaft, pull the old cam out through the center of the front gear, and then get to have fun with some extra long needle nose pliers trying to the the new one lined up right. Will I be able to do that, or am I going to have to remove the drive shaft and the front gear?

I went to a marina where one of the tech was going to help me out by removing the bushing, letting me have fun getting the new cam on, and then put the bushing back in for a few bucks. But when I got there, he was at lunch, and his boss basically told me I was an idiot, that there was no way I could replace the bushing without completely breaking down the lower unit (ie remove drive shaft, forward gear and bearing, plus the shift shaft assembly). He then told me he could sell me the two tools I'd need (shift shaft bushing tool and one for the top of the drive shaft) for $60, then made the implication i wasn't smart enough to handle it, so I should give him $120 (then up to $200 a few minutes later) plus parts to take care of it....

 

[carholme]

Re: 1978 Merc 800 Shift Cam

Before you waste money on other things, I would check to see how the ears are on the clutch and the reverse gear seen here as items 59 and 63. Poor shifting habits will cause the ears to round off, creating a reverse engagement problem.

http://www.crowleymarine.com/mercury-outboard/parts/484_19.cfm

As far as the shift cam goes, you say there is a deep groove worn in it. Here is a picture of a new cam:

http://img828.imageshack.us/img828/3793/glm11185.jpg

Mouse over the picture and you will be able to rotate it.

Gerry

 

[AugustMoose87]

Re: 1978 Merc 800 Shift Cam

I checked the gears and clutch pretty thoroughly, and they look almost band new. ears have near perfect 90 degree angles on them, and the gear teeth have so little wear you can just barely tell where they make contact with the drive shaft gear.

I can see in the pic that there is a bit of a groove in the new on, but from what I could see looking through the lower unit (and will hopefully confirm once I get it out) the groove on my cam was much deeper, and was even effecting where the two "plateaus" for the neutral and reverse position are (ie they are not as far forward and are more to the side of where they should be)

 

[merc850]

Re: 1978 Merc 800 Shift Cam

If you want to do it right you'll need to remove the propshaft and bearing carrier

then you can access the shift cam thru the FWD gear. This works best if the propshaft is horizontal: Remove the shiftshaft bushing and the shift shaft and pull it out, reach in and pull out cam to install put new cam in with top up (should be marked) push shiftshaft down its hole and locate into cam. Replace shiftshaft bushing.

 

[Faztbullet]

Re: 1978 Merc 800 Shift Cam

If you replace the cam put the newstyle follower in shaft as it will shift a whole lot better.....part #44532A 1

 

[AugustMoose87]

Re: 1978 Merc 800 Shift Cam

merc850 - thats exactly what I was wanting to hear. I have the prop shaft/bearing carrier out, and was thinking I'd be able to reaching in and work with the shift cam through/around the FWD gear and drive shaft pinion - the boss at that shop just made it sound like it was impossible to replace the cam without taking the drive shaft and FWD gear out as well.

faztbullet - thanks for the tip. Any way to tell the difference between the new and old style? Like I said, I'm almost positive the lower unit got some work done (as recently as 5-10 years - I've owned it for 3). The gears, clutch, and even follower all look pretty new, and I'd prefer not to replace it if there's no need

 

[Faztbullet]

Re: 1978 Merc 800 Shift Cam

Any way to tell the difference between the new and old style

Old is one solid piece and new is 2 pieces with 3 small ball bearings....

 

[AugustMoose87]

Re: 1978 Merc 800 Shift Cam

Glad I asked... Thanks for the tip, now I just need all my parts/tools to get here