WAJetboating
Member
As discussed in an earlier thread, I have had an intermittent low-RPM roughness since I first purchased my 2001 C2K with 240EFI engine. I thought I'd resolved it last year when I discovered a failed mechanical wire splice coming off my two-stick console, but the roughness resurfaced this season.
Given that 1) the roughness occurred around 2500 RPM {the magic threshold for the throttle guardian} and 2) the engine would continue to run roughly until the throttle was completely idled {suggesting some electronics were making decisions}, I suspected the throttle guardian was still at the root of the problem.
Intermittent problems are a bear to debug. To prepare, I cut the output lead of the throttle guardian and inserted a spade lug connection. This enabled me to quickly remove the throttle guardian from the circuit. Since it works by grounding out the CDI's, all I had to do was disconnect this one wire to eliminate any effect the throttle guardian might be having.
Then I just had to wait until the problem recurred. It eventually did, and while someone else manned the helm I dove behind the console and disconnected the spade lug connection. The engine instantly started running normally. Touching the connectors together again caused roughness; separating them caused smooth operation. It was 100% repeatable. I taped off the two connections and tucked them away, disconnected. The problem has not recurred since, during probably 10+ hours of engine operation.
With my boat's two-stick console, I have separate control of the thrust reverser (via a FNR lever) and the throttle (via a throttle lever). There is a mechanical interlock that prevents dangerous configurations such as moving the FNR lever out of F or R when the throttle is anywhere but at idle. Another mechanically impossible setup is to advance the throttle off of idle when the FNR lever is in neutral.
None of these prohibited operations are dependent upon the throttle guardian; they are enforced by the two-stick console. So disabling the throttle guardian really doesn't have any operational impact on the boat.
That left one question: Was the throttle guardian part of the "Don't start the engine out of neutral" circuit? I didn't think so, but it's important to not start the engine in Forward or Reverse because you don't want to suddenly lunge forward or backward.
So I performed that test. Result: The engine will not start. It won't even crank.
This is GOOD news, because it means the throttle guardian is unnecessary and can be left out of the system. Its whole purpose in life is to prevent RPM's from exceeding ~2500 if the FNR lever is in neutral. Well, on my two-stick console, that condition is prevented mechanically - I cannot advance the throttle off idle when the FNR lever is in neutral. So that function of the throttle guardian should never be invoked.
As we've seen, though, the throttle guardian can rear its ugly head when it is NOT supposed to. That has caused me weird, intermittent engine roughness since Day One of my ownership. But since I disabled it, I haven't had a single issue.
Now that I've confirmed that the throttle guardian does not play a role in preventing the engine from starting when the FNR lever is out of neutral, it truly has no role in my boat. It's disconnected, and it's going to stay that way.
Hope this helps someone!
Given that 1) the roughness occurred around 2500 RPM {the magic threshold for the throttle guardian} and 2) the engine would continue to run roughly until the throttle was completely idled {suggesting some electronics were making decisions}, I suspected the throttle guardian was still at the root of the problem.
Intermittent problems are a bear to debug. To prepare, I cut the output lead of the throttle guardian and inserted a spade lug connection. This enabled me to quickly remove the throttle guardian from the circuit. Since it works by grounding out the CDI's, all I had to do was disconnect this one wire to eliminate any effect the throttle guardian might be having.
Then I just had to wait until the problem recurred. It eventually did, and while someone else manned the helm I dove behind the console and disconnected the spade lug connection. The engine instantly started running normally. Touching the connectors together again caused roughness; separating them caused smooth operation. It was 100% repeatable. I taped off the two connections and tucked them away, disconnected. The problem has not recurred since, during probably 10+ hours of engine operation.
With my boat's two-stick console, I have separate control of the thrust reverser (via a FNR lever) and the throttle (via a throttle lever). There is a mechanical interlock that prevents dangerous configurations such as moving the FNR lever out of F or R when the throttle is anywhere but at idle. Another mechanically impossible setup is to advance the throttle off of idle when the FNR lever is in neutral.
None of these prohibited operations are dependent upon the throttle guardian; they are enforced by the two-stick console. So disabling the throttle guardian really doesn't have any operational impact on the boat.
That left one question: Was the throttle guardian part of the "Don't start the engine out of neutral" circuit? I didn't think so, but it's important to not start the engine in Forward or Reverse because you don't want to suddenly lunge forward or backward.
So I performed that test. Result: The engine will not start. It won't even crank.
This is GOOD news, because it means the throttle guardian is unnecessary and can be left out of the system. Its whole purpose in life is to prevent RPM's from exceeding ~2500 if the FNR lever is in neutral. Well, on my two-stick console, that condition is prevented mechanically - I cannot advance the throttle off idle when the FNR lever is in neutral. So that function of the throttle guardian should never be invoked.
As we've seen, though, the throttle guardian can rear its ugly head when it is NOT supposed to. That has caused me weird, intermittent engine roughness since Day One of my ownership. But since I disabled it, I haven't had a single issue.
Now that I've confirmed that the throttle guardian does not play a role in preventing the engine from starting when the FNR lever is out of neutral, it truly has no role in my boat. It's disconnected, and it's going to stay that way.
Hope this helps someone!
