1993 Force 40hp jumps

[Dale Lyons]

Hi, I have a 40hp Force (1993) outboard that in the higher rpm range (in forward gear) it periodically "jumps". The motor jumps from the water and you can feel this thru out the boat. My son-in-law suggested that the female driveshaft spline mounted on the crankshaft of the powerhead may be cracked, allowing the driveshaft to slip. I removed the powerhead and I see no evidence of a cracked or worn spline. I then took the gear housing apart in the lower unit and I found no obvious damage there either. Has anyone had any experience with this type of problem? Thank you for your help.

 

[ferdly1]

Re: 1993 Force 40hp jumps

Sounds to me like a bad dog clutch and forward gear. There is a name for this called stumpknocking, feels like you hit a stump. Did you take the lower unit apart and closely examine the clutch and forward gear. Any wear will cause this. Hope this helps.

 

[Dale Lyons]

Re: 1993 Force 40hp jumps

I really wish to thank ferdly1, you hit my problem right on the head. After inspecting the gears in the lower unit,I did see some wear. I brought the clutch dog and the forward gear to a machine shop. The machinist wasn't sure he could re-cut the faces on the parts ( he said they were really hard steel) but he gave it a try. I put everything back together and there wasn't any stumpknocking any more !!! So again, many thanks to ferdly1. D. Lyons