Johnson 18 hp slipping out of gear ?

I got my old Johnson running and now when going past half throttle it seems to slip out of fear. It seems to do O K at low speed, but when you try to go faster, the engine seems to rev up and the boat slows down. If it was the shear pin, it would not work at low speed, would it ? It was running fine until I went up in the throttle. I can't figure it out ! Any body got any ideas?

Re: Johnson 18 hp slipping out of gear ?

Model number?<br /><br />Does it clunk when it "slips"?<br /><br />Does it do it in reverse?<br /><br />Have you removed the prop to inspect the shear pin?<br /><br />Let us know.

Re: Johnson 18 hp slipping out of gear ?

You may have a spun hub on the prop or possibly a ventilation problem. Mark across the hub underneath the prop, drive the boat and check the mark.it should indicate if the hub is slipping.<br />A visual inspection may also show indications of a spun hub.

Re: Johnson 18 hp slipping out of gear ?

JeffC,If the boat just slows down when higher RPMs are applied it is likely as suggested a shear pin problem or spun hub.Some shear pins will grab when sheared at lower RPMs.If engine kicks completely out of gear when applying high RPMs you may have a problem with a worn shift dawg,gear lobes worn down, or linkage is out of adjustment.

Re: Johnson 18 hp slipping out of gear ?

Thanks JB, Steelespike and OB, -- JB - model FD- 18E , no clunking just just kind of sounds like it went into neutral. Reverse seems to be fine, but of course I can't go to fast in reverse. I was thinking more on the line of a shear pin myself. but then I thought that would keep the prop from spinning all together. After getting a manual, The spun hub thing sounds more like a possibility. I went out and took it (the motor) off the boat and brought it up to the house to look at while sitting at the picinic table and enjoying a cold one, ICE TEA that is. And what I found was that there was NO cotter pin in the hub. I unscrewed it and removed the prop, the shear pin WAS in place. Do you think that it was just that the cotter pin was missing, and that at high speed the prop came back just enough to come away from the shear pin ? I'm probably lucky that the hub did not fall off in the lake, YEAH !!