1965 Mercury 500 shifting problems

[1958scottguy]

I have a 1965 Mercury 500 that will not shift. For some reason when the lower unit is on the outboard, it will not shift. Sometimes the shifter on the control box will get stuck and the lower unit has to be removed in order for it to move freely again. When the lower unit is off I can move the shift shaft through FNR, but as soon it is back on the motor it will not shift (it stays in the same gear as when I put it on when I go through FNR on the control box.) I find this puzzling because a few weeks ago I replaced the impeller and threw the lower unit on without the water pump or reverse lock cams in the motor and it shifted fine. Since then I've put everything back together it has not shifted. I have also noticed that it is shifting somewhat harder(on the control box) than it should be even though it is not shifting threw the gears. I received the motor with the lower unit removed so I had no idea if there was anything wrong with it. The owner told me it ran like a champ last season on the water. Any ideas on why it is not shifting?

On a unrelated note what does the reverse lock cam do and could this be causing the problem?

 

[carholme]

Re: 1965 Mercury 500 shifting problems

Do you have the s/n of your engine?

The reverse lock cam prevents the engine from raising upwards when in Neutral or reverse. It is disengaged when in forward. There is a possibility that the cam has been installed in the wrong position or the boat and engine were not in the same gear when the LU was installed. Can provide more information when we get your s/n.

Gerry

 

[1958scottguy]

Re: 1965 Mercury 500 shifting problems

The serial number is 1773674.

 

[carholme]

Re: 1965 Mercury 500 shifting problems

Yes it is a 1965:

50 1965 Short & Long 1755549 - 1870388

From here:

50 1965 Short & Long 1755549 - 1870388

Parts List:

MERC 500 - Mercury, Mercruiser, Force, etc. Parts Lookup

See the reverse lock cam as items 17/18 under GEAR HOUSING ASSEMBLY, COMPLETE (PAGE 1) which actuates items 6/7/8/9 and 10 under DRIVE SHAFT HOUSING ASSEMBLY, which actuates Reverse Lock Assy, item 13 under CLAMP AND SWIVEL BRACKET ASSEMBLY .

The older engines had a two piece reverse cam (metal) whereas the newer ones had a composite single piece cam.


The service manual you require for your engine is P/N: 90-25500 which you can search for on Ebay, but they are getting scarce and people are asking high dollars for them.

In the interim, here is a link to the condensed version of the Clymer manual. Download it soonest to your computer as the link is short lived.

MERCURY - MERCURY FOUR & SIX CYLINDER MODELS (1955-1965).: Small Engine Repair Reference Center Home

It does not have the pictures of the reverse cam, so I will add the 1969+ engines to show you the pictures:

MERCURY - MERCURY FOUR-CYLINDER MODELS (1969-1989).: Small Engine Repair Reference Center Home

See the two types of reverse cam on page 287 as Fig M12-63 (two piece) and Fig M12-64, (newer one piece).

Sorry for this being so long and after you have managed to get through it all, do not hesitate to return with any questions.


Gerry

 

[1958scottguy]

Re: 1965 Mercury 500 shifting problems

Thank you for the information. I will see if it is the reverse lock cam.