1979 Mercury 402 40hp Reverse Gear issues

[MacDaddy21]

Having some trouble with my reverse gear in my 79 402 40hp. Shifts into forward gear fine, but Reverse is a little different. It makes some grinding noises, and is a little clunky sounding when it first drops into reverse. I haven't torn into the lower unit yet, but I've rebuilt nearly everything else on the motor, so I'm not worried about getting into it. I'm just curious what could be causing this trouble, and what to look for when I tear into it. Any advice is appreciated.

 

[carholme]

Re: 1979 Mercury 402 40hp Reverse Gear issues

MacDaddy;

Barring rigging problems, could be just the clutch teeth slightly rounding off, item 59 here:

http://www.crowleymarine.com/mercury-outboard/parts/489_19.cfm

You can clean them up yourself if you have a Dremel tool but I see it is available at $44 which gives you new teeth edges in Forward and Reverse, if that is the problem.

Gerry

 

[MacDaddy21]

Re: 1979 Mercury 402 40hp Reverse Gear issues

I'll check into that. As you can tell, I finally got the ol' 40 on the water and it runs like a top. Good little motor. Thanks for all the wiring assistance you gave me. It really helped out.

 

[MacDaddy21]

Re: 1979 Mercury 402 40hp Reverse Gear issues

What is the easiest way to tell if the clutch needs replacing though?

 

[carholme]

Re: 1979 Mercury 402 40hp Reverse Gear issues

When you get it apart, as you are having a problem with Reverse, you should notice the teeth edges will be more rounded on the reverse side than the forward gear side. The clutch has teeth on both sides which mesh with the same teeth in the Forward and Reverse gears.

I'll see if I can dig up a schematic somewhere to show you the setup.

Gerry

 

[MacDaddy21]

Re: 1979 Mercury 402 40hp Reverse Gear issues

that would be great, thanks Gerry.

 

[carholme]

Re: 1979 Mercury 402 40hp Reverse Gear issues

Here is a link to a different engine but virtually the same as yours as far as the views of the clutch and gear arrangement. If you start about page 6A-16 thru 19, you should be able to make out the defined teeth (jaws) on the clutch and the two gears. You will also see the main reasons for rounded gears.

http://1manual.com/Mercury manuals/Service Manual PDFs/TwoStroke/852572r1/6a.pdf

Hope it helps you understand what you will find in yours. See that the clutch slides on the prop shaft as selection is made between F/N/R.

Gerry

 

[Wingedwheel]

Re: 1979 Mercury 402 40hp Reverse Gear issues

Could also be a worn shift cam and/or follower, stretched cable ect. See if you can shift in into reverse by hand with the cable disconnected. Thats a good place to start.

 

[MacDaddy21]

Re: 1979 Mercury 402 40hp Reverse Gear issues

Thanks Gerry, I'll give that a shot.

Wingedwheel, I replaced my cables and a lot of the shift assembly with one that was in much better condition. When I pull the lever into reverse, there is no friction or difficulty moving the lever. I just move the lever very slowly so I don't grind unnecessarily. I think it is gear related, and I'd like to see what it looks like in there just for personal knowledge.

Gerry, don't know if you will know this, but I am wondering if you could tell me if the parts from my other LU will work to swap. Before you ask "why don't I just swap the LU's?" Well, the one off my parts motor has a broken skeg, and has a chunk missing out of the cavitation plate, so I dont really want to use it, but the marine dealer I got it from said they went through it and it was solid. Whether or not that is true, I guess I will have to wait and see. But I'll give you the serial #'s and if you could check compatibility that would be awesome.

1979 402 Motor (on boat) - 5253808
1980 402 parts motor - 5661617

 

[carholme]

Re: 1979 Mercury 402 40hp Reverse Gear issues

Here are the prop shaft area parts lists for both s/ns:

5253808:

http://www.crowleymarine.com/mercury-outboard/parts/489_19.cfm

5661617

http://www.crowleymarine.com/mercury-outboard/parts/673_180.cfm

I just did a brief check but the clutch, F/R gears are the same p/ns for both so I don't think you will have a problem at all.

Gerry