1980 80hp jumping in and out of gear when in forward

[mcurcio1989]

When you put the engine is operated on a hose it runs perfect. Then when you put a load on it in forward (Aka when it is in the water) its like the sliding clutch is jumping on the forward gear. It idles fine in gear but with the application of much power it starts jumping. This is violent and not like a mis. I am trying to visualize what could cause this but I'm stumped.

I bought this motor last year. It had some carb issues that took half the year to get hashed out. I finally got it running good and put it in the water. It ran great for a mile. Had plenty of power etc. Then I went to take off and it started doing what I have described. I thought it was an electrical mis so I went through all of the possibilities there. I had a bad rectifier so I replaced that. The lower unit was leaking oil / water so I rebuilt it with all new seals and o rings. Just got it back together tonight. I put it in and the engine ran fine but it was still jumping and no I am certain it is something in the lower unit. This time it will jump and sometimes it even continues to skip as liek the sound of a blown gear but then it grabs as soon as power is pulled from it. When I pulled it apart everything looked good. No bad bearings or excessive wear on the teeth. The only thing bad was the little cross pin slide was broken at the middle where the pin goes through. I replaced that. Any ideas or thoughts would be greatly appreciated!

 

[orbanp]

Re: 1980 80hp jumping in and out of gear when in forward

If the dog clutch is fine and not worn, then possibly the shifting mechanism is maladjusted and does not let the gear engage fully in forward.
Double check the shifting mechanism!

Peter

 

[emckelvy]

Re: 1980 80hp jumping in and out of gear when in forward

Did you get the very stiff spring in behind the shift clutch roll pin (the pin that was busted)?

This spring puts tension on the shift clutch when you're in Fwd gear, and if you don' t have it there (or it's on the wrong side), you won't have a proper gear. I imagine it would jump out of gear badly.

Check out the attached diagrams for a parts breakdown. The clutch spring is inserted into the end of the propshaft first, followed by the cross-pin slide. You can see where the spring fits onto the slide. You have to push the spring and slide into the propshaft and simutaneously align the shift clutch pin holes with the hole in the cross-pin slide. Install the roll pin, thru the clutch and make sure it's installed flush. Then the retaining spring is "wound" back into place on the shift clutch.

Once this is done, you'll note that if you attempt to pull the shift clutch towards the threaded end of the propshaft, there's an awful lot of pressure resisting your pull. This spring pressure is what forces the shift clutch into the gear when you're in Fwd.

I can't ever recall one of these L/U's jumping out of Fwd gear (as long as it was adjusted properly), so I'd bet it's an assembly problem.

HTH & let us know what you find.........ed

 

[mcurcio1989]

Re: 1980 80hp jumping in and out of gear when in forward

Thanks for the advice guys - I did some trouble shooting last night and found the problem.

I adjusted the shifter to see if it wasn't going in all the way and that did nothing. So I decided it was time to yank the guts back out of the lower unit. It came apart super easy since I had just had it apart. I immediately saw the problem. The notches on the forward gear and the shift clutch that are supposed to engage with each other are severely rounded out. This is clearly the problem. Reverse gear even has some notable wear on them as well. I didn't look at these when I had it out before, I inspected the bearings and gear teeth. There was metal shavings in the oil when I drained it the first time and I was trying to figure out where it came from. I don't really know how I missed that.

I am debating what I want to do now. I need to replace the forward and reverse gear, and sliding clutch and I will probably throw a new spring in for good measure. This motor is for a pontoon boat and I have a spare 25hp motor that I can throw on there and get by. I have a seaplane kit which is going to be taking up all of my time and money when I get it in 3 weeks so I am thinking it may be best to wait until mid summer when I am done building the plane to throw the money at this but not sure yet.

 

[mcurcio1989]

Re: 1980 80hp jumping in and out of gear when in forward

Other question I have. How is the seal on the shifter replaced? It has what looks like a round carrier with slots on the top presumably for unthreading it. I don't really see any threads though so I wanted to verify that that is how it is removed. After I did the seals on the drive shaft and prop shaft. I air tested it and saw it was leaking from the shifter shaft. I was hoping everything would be in order so I was going to do a quick test run and then pull the lower unit again to do the shifter seal. Obviously its not the only thing I need to do now but that was why I wanted to test it before waiting another week for a stupid seal.

Also the engine needs to be tuned in the water as it is wanting to stall when placed in forward. I know this sounds kind of weird but I'm thinking I'm going to throw it all back together and get that all tuned up good on the lower end. Rather than doing it when I have the fresh new gears. It holds in gear fine when at idle so I figure better to put wear on these junk gears than do it with the new ones. Any thoughts on that?