thanks all. I have actually read all the adult pages. I was considering trying to do something like
this myself to see if it fixed, but looking at the engine scared me off a bit. I couldn't even locate the interrupt switch
I'm in Iowa, on one of our few private lakes, and I think it may be a challenge to find a good mechanic. I got the number for a mobile mechanic and he started saying how he doesn't do lower unit work and such which concerned me, but maybe I'll give him a try.
But what I'm hearing is that this should definitely not be something I accept and try to live with.
OK, that's my video. ("And as always, thanks for watching.")
First thing, what is your engine serial number. We ask this of every thread as it allows the people helping you to know exactly what we are all working with.
Second. You need to understand how the system works. Here's a brief overview.
The dogs on the clutches (in the gear housing) are undercut. That means with load on the propeller, like when the engine is pushing the boat, the clutch tries to pull itself into engagement. This stops the torque of the engine forcing the drive out of gear. That's important for high torque engines, especially 5.7 and BBC engines. A consequence of this is that when the prop has load, pulling the clutch out of engagement is difficult/near impossible. The solution is the 'shift interrupt switch'. This switch kills the spark for long enough to get the clutch disengaged, and then allows the engine to keep running again. Here's the tricky part. The lower shift cable arrives up at the shift plate on the engine and attaches to a point on the lever that is offset to the lever pivot point. When there's load on the prop and the operator tries to shift out of gear, the load on the cable and its offset mounting point force the lever to move. That closes the switch that grounds the ignition system, causing the torque to be removed from the propeller shaft, allowing the clutch to disengage, which removes the load from the cable, and the lever is sprung back to the 'rest' position, the switch opens and the engine merely hiccups and continues to run. All that happens in a blink of an eye, literally less than 1/2 a second. And it's that load on the prop that starts it all. When running on flushers, there is no load on the prop, so no interrupt when shifting... If you DO get an interrupt when shifting while running on flushers, there's something wrong with the system. And the interrupt only works coming OUT of gear (and that's either reverse or forward). It does not operate when going into gear (the last thing you need when adding a sudden load to an engine is for some fool to be shutting off the spark! :facepalm
Whenever I service a boat, one test I do when running on the flushers is to just press down, then pull up on the lever to check the switch is working, in both directions. I need to hear that hesitation. That's the first place I recommend you start. Verify the switch working. The next thing is the adjustment of the switch with relation to the lever. It does need to be right, and there is a spec.
If you have a plunger type switch, like the one I'm working on in my video, then the spec is 3mm (1/8"). The switch needs to close when the plunger has moved 3mm. If it's too far, the lever may never trip it. Use a 3mm drill bit to check the distance.
Chris.......
