strange gear slip when warm

[neversinksmith]

hey gang. so I made a good trade for a 1973 merc 850 85hp outboard. after some tinkering ive got her running like a champ in the test tank. when I put her in the water I immediately realized I had almost nothing in reverse. no grinding noise but only slight movement backwards. forward worked proper. I ran it at the islands for a few days w/ no issues until I ran about 10 mins in forward at very slow speed. then when I punched it, she revved way up but the prop wasn't spinning(or propelling me forward). got back to the slip at low speed. the next day I fired her up and no issues or slipping in forward. im stumped. im guessing it had something to do w the gear oil being hot and thinner after a 10 min at low rpms. (aside from obviousle a gear/clutch dog issue).

any ideas? thanks

 

[Outsider]

Spun prop ... ?

 

[Chris1956]

Bad shift cable or shift rod adjustment can give no reverse.....

 

[Chinewalker]

Gears are under water - very hard for them to get hot. And, if the "slip", you'll know it, as it won't be silent. My bet is on either a fouled prop (weeds, plastic bag, etc.) or a spun hub.

 

[neversinksmith]

if it was a spun hub, wouldn't it do the same thing in forward as its doing in reverse?

 

[neversinksmith]

changed out the worn clutch dog. got reverse again. any idea why it would slip in forward after a 10 minute slow speed run but run perfect other times?