1984 40 hp Johnson slow in reverse

[amishboy]

I have a good running 40 hp Johnson on my 21' pontoon. First time I put it in the water this year, it is going very slow in reverse, regardless of rpms. Last year if I put any throttle at all on it, wanted to shoot motor right out of water. Was winterized and put in new lower unit oil before starting out. No metal shavings. We are in a shallow dock and prop did catch a little backing out. Does fine in forward. What's my checklist for figuring this out?

 

[Mel Taylor]

My guess (and it's only a guess) is that you are experiencing the first stages of a spun prop. The first time I had a spun prop on my 25 horse 1884 Evinrude that's exactly the way it acted. After a few days it was no longer doing so fine in forward. As long as I took it slow it would propel the boat. As soon as I cranked up the RPMs, the boat would stop moving.

BTW, this is not something you can check for by leaving it in gear with the motor shut down and trying to turn the prop by hand. You might be wise to carry a spare prop and tools to change it.