Got a 180 HP 3.7LX in the spring. First time on the lake I noticed 3 things that landed outside the range of what I would consider normal functioning or performance. 1) Overcharging, 2) poor warm idle (for example, cuts out when waiting in line at the dock), and 3) no WOT. The only remaining problem (for now
) is no WOT, and boy has it been a head scratcher.
Here is what happens when advancing the throttle:
0 - 1/2 throttle: big torque, jumps up on plane
1/2 - 3/4 throttle: speed increases consistent with throttle
Trim up: speed and RPMs increase until maxing out at the sweet spot around 3800 on the dash tach
3/4+ throttle: instantaneous bog with a linear power loss the farther past 3/4 throttle you go.
No transition, no stumbling, just an infinite boggy groan. If you pull back on the throttle even a cm, immediately jumps back to life. It does not take a second or two to "catch up" after doing this, it picks up right where it left off. This happens at precisely the same point whether you approach 3/4 throttle slowly and gingerly or at a medium-fast rate (like you might for most towables). Not accelerator pump for many reasons. The fact that this happens at the same throttle position so precisely and predictably whether warm or cold, pre or post carb cleaning, with on-boat fuel or auxiliary tank fuel, etc. leads me to believe the underlying issue is mechanistic (for lack of a better term). In other words, something different happens at that point that wasn't happening at all or to any degree before reaching that point. With that in mind I've narrowed it down to two suspects, because everything else I can think of either happens progressively or manifests with variability.
To test the ignition:
Is there any harm in pushing it to WOT in neutral? This is my first boat so I've been scared to go past 1/3 throttle on muffs simply because it seems scary. What about in the water? I'm asking because I think that would help me rule out ignition/spark issues that manifest at a particular RPM. For example, a faulty ignition module or short to ground (at the tach?) should not be load dependent and should therefore occur in neutral, correct? All the other possible problems related to ignition/timing that I can think of would happen either constantly or progressively. The issue I'm experiencing is like a light switch: smooth and consistent power band from idle to 3/4 throttle then immediately hits a wall. No transition, no stumbling, just an infinite boggy groan.
To test the secondaries:
To test if the issue is somehow related to the opening of the secondaries I came up with the idea to lockout (or tighten down the spring) on the air valve to the secondaries. As I understand it, the opening of the secondary throttle plates merely allow the airflow demanded by the engine to act on the air valves, and it is the position of the air valves--not the throttle plates--that dictate how much fuel/air is delivered. If I am understanding this correctly, wouldn't preventing the secondary air valves from opening essentially make it function like a 2 barrel carb? If this is true, and the issue was indeed related to the secondaries, in theory I should then be able to achieve WOT albeit with less available HP and lower top speed, yes?
Thanks for helping me out or talking me through this. All is appreciated.
) is no WOT, and boy has it been a head scratcher.Here is what happens when advancing the throttle:
0 - 1/2 throttle: big torque, jumps up on plane
1/2 - 3/4 throttle: speed increases consistent with throttle
Trim up: speed and RPMs increase until maxing out at the sweet spot around 3800 on the dash tach
3/4+ throttle: instantaneous bog with a linear power loss the farther past 3/4 throttle you go.
No transition, no stumbling, just an infinite boggy groan. If you pull back on the throttle even a cm, immediately jumps back to life. It does not take a second or two to "catch up" after doing this, it picks up right where it left off. This happens at precisely the same point whether you approach 3/4 throttle slowly and gingerly or at a medium-fast rate (like you might for most towables). Not accelerator pump for many reasons. The fact that this happens at the same throttle position so precisely and predictably whether warm or cold, pre or post carb cleaning, with on-boat fuel or auxiliary tank fuel, etc. leads me to believe the underlying issue is mechanistic (for lack of a better term). In other words, something different happens at that point that wasn't happening at all or to any degree before reaching that point. With that in mind I've narrowed it down to two suspects, because everything else I can think of either happens progressively or manifests with variability.
To test the ignition:
Is there any harm in pushing it to WOT in neutral? This is my first boat so I've been scared to go past 1/3 throttle on muffs simply because it seems scary. What about in the water? I'm asking because I think that would help me rule out ignition/spark issues that manifest at a particular RPM. For example, a faulty ignition module or short to ground (at the tach?) should not be load dependent and should therefore occur in neutral, correct? All the other possible problems related to ignition/timing that I can think of would happen either constantly or progressively. The issue I'm experiencing is like a light switch: smooth and consistent power band from idle to 3/4 throttle then immediately hits a wall. No transition, no stumbling, just an infinite boggy groan.
To test the secondaries:
To test if the issue is somehow related to the opening of the secondaries I came up with the idea to lockout (or tighten down the spring) on the air valve to the secondaries. As I understand it, the opening of the secondary throttle plates merely allow the airflow demanded by the engine to act on the air valves, and it is the position of the air valves--not the throttle plates--that dictate how much fuel/air is delivered. If I am understanding this correctly, wouldn't preventing the secondary air valves from opening essentially make it function like a 2 barrel carb? If this is true, and the issue was indeed related to the secondaries, in theory I should then be able to achieve WOT albeit with less available HP and lower top speed, yes?
Thanks for helping me out or talking me through this. All is appreciated.
