Broke lower unit?

[belairbrian]

This is a 99 Force 40hp outboard on a 20 ft pontoon. First time out with this boat.

I was on the river yesterday and first trip out was fine. WOT was 5000 speed 15 mph.

Came back in for a while and went back out and had 3 other people on and boat was running About 14 mph.

Suddenly speed slowed to around 8 mph and rpms were 5200.

Headed back to the dock at half throttle (speed was about 8 mph at 3000 rpm)

Pulled the boat out and found that in neutral the prop can be turned both ways. In reverse it locks in and cant be turned.

In forward it cant be turned counter clockwise but will turn clockwise with a clicking sound.

Thoughts.

 

[pnwboat]

Re: Broke lower unit?

Was the motor jumping or jerking when you were turning 5200 at 8 mph? That's a sign that the clutch dogs might be slipping. Could be a simple cable adjustment or rounded off clutch dogs.

If not, I would suspect that the hub in the center of the prop is spun. The center spins at whatever RPM the engine is turning the propeller shaft, but the blades themselves are turning at a much slower rate. Put a mark on the metal outer part of the hub that the blades are connected to and a mark on the inner hub next to the propeller shaft/nut. Note they way the marks are oriented. Take the boat out and try to duplicate what you experienced earlier. If it happens again, look at the two marks. If they've moved, then you have a spun hub.

 

[belairbrian]

Re: Broke lower unit?

I've done some more reading and found that the ratcheting with the motor in forward (engine off of course) is normal. The ratchet allows the prop to spin free on a rapid deceleration where the water moving across the prop is trying to spin the prop faster than the motor shaft.

Hope I said that right.

Also I found the lower bolt on the fuel pump loose. The PO had it rebuilt (or did it himself) and put bolts in wrong longs and shorts were swapped. Fixing that changed the idle speed.

Still want to check the prop and see if it has a hub problem. Wouldn't be surprised, OP gave me his "spare" prop and it was pretty beat and current one has some dings as well

 

[Frank Acampora]

Re: Broke lower unit?

The clicking noise in forward gear is normal. It is NOT a design feature to allow the prop to spin freely. The drive dogs on the forward gear and dog clutch are "ramped" like a saw tooth to allow easier engagement into forward gear. Because the rear of the dogs are much lower than the front, they will ride over each other and drop back down with a clicking noise when reverse loads are applied to the prop.