Re: 40 hp 4 cyl Merc stalls instantly at full throttle
It's beginning to look like I've got the same problem you have, whatever it might be. After a thorough fuel system check, the thing magically started and ran fine at varying throttle settings for 20 minutes. As I was returning to the dock, it "burped" once, but kept running -- as if a small slug of water got into the carbs. At the dock, while it was idling, it shut off immediately, as if the key or kill switch had turned it off.
It wouldn't start, so I checked the spark -- nada, zilch. The drinking lamp was lit by then, though, so I'm going to attack it again today. Here are my thoughts:
Kill switch circuit? - disable it altogether and test. I would really like this to be the problem, but I'm not optimistic.
Other? - possibly a heat-related component breakdown. When I use the boat, I seldom run it wide open, and it's never failed, except during this test, when I ran it at WOT for a while. The owner has a lead foot, though, and it's failed 3 times for her.
It's got to be something common to all cylinders, which limits it to the stator, trigger, stator adapter module (it's got a red stator), rectifier/regulator, and switch box -- in other words, just about everything in the ignition system. Since it only fails (it seems) when hot, it's going to be a ***** to troubleshoot.
If anyone has any thoughts about which of all these parts has a reputation for failing, I'd like to hear about it.
I'll keep you posted.
It's beginning to look like I've got the same problem you have, whatever it might be. After a thorough fuel system check, the thing magically started and ran fine at varying throttle settings for 20 minutes. As I was returning to the dock, it "burped" once, but kept running -- as if a small slug of water got into the carbs. At the dock, while it was idling, it shut off immediately, as if the key or kill switch had turned it off.
It wouldn't start, so I checked the spark -- nada, zilch. The drinking lamp was lit by then, though, so I'm going to attack it again today. Here are my thoughts:
Kill switch circuit? - disable it altogether and test. I would really like this to be the problem, but I'm not optimistic.
Other? - possibly a heat-related component breakdown. When I use the boat, I seldom run it wide open, and it's never failed, except during this test, when I ran it at WOT for a while. The owner has a lead foot, though, and it's failed 3 times for her.
It's got to be something common to all cylinders, which limits it to the stator, trigger, stator adapter module (it's got a red stator), rectifier/regulator, and switch box -- in other words, just about everything in the ignition system. Since it only fails (it seems) when hot, it's going to be a ***** to troubleshoot.
If anyone has any thoughts about which of all these parts has a reputation for failing, I'd like to hear about it.
I'll keep you posted.