Ugarph1982
Cadet
- Joined
- Apr 8, 2017
- Messages
- 16
Hey everyone!
I have a 1988 Mercruiser 3.7L 165 HP (B954661) in a 1988 Celebrity Crownline. I've been having a great time with the boat this summer, but I've been experiencing a pesky issue related to the ignition. The basic symptom is that the tachometer is bouncing around a bit and the engine feels like it's missing in direct accordance with the tachometer shenanigans. While there isn't any popping or backfiring, the tone of the engine will change slightly and the boat will decelerate for a split second just enough where my passengers give me a funny look. It does not always occur. Most of the time, in cruise, the engine runs as smoothly as a baby's butt. It's also worth noting that I can see this at the beginning of the first run in the morning, or after the engine has been at temp for a while. Also, none of the other gauges are jumping around.
One time, we had just pulled away from shore after a 30 minute break and had been underway for about 45 seconds and the motor missed a couple of times and then quit "dead as a hammer" at about 30 MPH ... At first I was thinking, "great, vapor lock ... time to get out the cold rags" .... But, when I took it out of gear to attempt to restart it, it cranked right back up and we took off. It missed and stumbled a few times once we got back up to speed, but I blipped the throttle a couple of times and then it cleared up. Also, I noticed the tach jumping around right before it quit. Hmmmmm ... maybe it is a sticky shift interrupter switch. Maybe not.
Moreover, this past weekend the tachometer began reading consistently 1000 - 2000 RPM's higher than the engine was actually running. It mainly displayed this symptom when I was in and out of gear trying to teach someone how to get up on skis. It cleared up and went back to a more accurate reading after shutting down for a few minutes. I feel like the engine was having a harder time at idle as well while it was doing this; even though that could have partially been a little vapor locking.
The boat has the Pertonix ignition (1146A) and the flamethrower 3.0 ohm coil. Both are new this year. The distributer cap, rotor, wires, and plugs are also new this year. The boat has a Breezeworks alt kit on it that reads a steady 14.2 volts.
There are a couple of things I want to rule out and this is where my question comes in. I would like to rule out the tachometer (which is original and has a loudly ticking and inaccurate hour meter) and also the shift interrupter switch.
1) For the tachometer ... where should I unhook it to make sure that it's not shorting out the ignition? The grey lead on the back of the gauge? The grey lead on the coil (Not sure about that because the wiring diagram indicates that the shift interrupter switch is spliced into it)?
2) The shift interrupter switch. I know most people say this shouldn't affect the ignition with the boat fully in gear, but I need to rule it out and make sure it's not sticking. Plus, several folks have talked of similar issues and claimed that this was their problem. I have the original switch, but might consider the new kit (8643536A1) if I need to replace it. Perhaps the existing switch could be adjusted??? If I wanted bypass it to make sure it's not causing the problem, how would I do that? Disconnect leads and splice together, or simply disconnect them? I'm no electrician, but it looks like that circuit provides system ground to the ignition. I realize that I have to shut off the ignition to get the boat out of either gear while I'm running this test.
Any other advice would be greatly appreciated!
I have a 1988 Mercruiser 3.7L 165 HP (B954661) in a 1988 Celebrity Crownline. I've been having a great time with the boat this summer, but I've been experiencing a pesky issue related to the ignition. The basic symptom is that the tachometer is bouncing around a bit and the engine feels like it's missing in direct accordance with the tachometer shenanigans. While there isn't any popping or backfiring, the tone of the engine will change slightly and the boat will decelerate for a split second just enough where my passengers give me a funny look. It does not always occur. Most of the time, in cruise, the engine runs as smoothly as a baby's butt. It's also worth noting that I can see this at the beginning of the first run in the morning, or after the engine has been at temp for a while. Also, none of the other gauges are jumping around.
One time, we had just pulled away from shore after a 30 minute break and had been underway for about 45 seconds and the motor missed a couple of times and then quit "dead as a hammer" at about 30 MPH ... At first I was thinking, "great, vapor lock ... time to get out the cold rags" .... But, when I took it out of gear to attempt to restart it, it cranked right back up and we took off. It missed and stumbled a few times once we got back up to speed, but I blipped the throttle a couple of times and then it cleared up. Also, I noticed the tach jumping around right before it quit. Hmmmmm ... maybe it is a sticky shift interrupter switch. Maybe not.
Moreover, this past weekend the tachometer began reading consistently 1000 - 2000 RPM's higher than the engine was actually running. It mainly displayed this symptom when I was in and out of gear trying to teach someone how to get up on skis. It cleared up and went back to a more accurate reading after shutting down for a few minutes. I feel like the engine was having a harder time at idle as well while it was doing this; even though that could have partially been a little vapor locking.
The boat has the Pertonix ignition (1146A) and the flamethrower 3.0 ohm coil. Both are new this year. The distributer cap, rotor, wires, and plugs are also new this year. The boat has a Breezeworks alt kit on it that reads a steady 14.2 volts.
There are a couple of things I want to rule out and this is where my question comes in. I would like to rule out the tachometer (which is original and has a loudly ticking and inaccurate hour meter) and also the shift interrupter switch.
1) For the tachometer ... where should I unhook it to make sure that it's not shorting out the ignition? The grey lead on the back of the gauge? The grey lead on the coil (Not sure about that because the wiring diagram indicates that the shift interrupter switch is spliced into it)?
2) The shift interrupter switch. I know most people say this shouldn't affect the ignition with the boat fully in gear, but I need to rule it out and make sure it's not sticking. Plus, several folks have talked of similar issues and claimed that this was their problem. I have the original switch, but might consider the new kit (8643536A1) if I need to replace it. Perhaps the existing switch could be adjusted??? If I wanted bypass it to make sure it's not causing the problem, how would I do that? Disconnect leads and splice together, or simply disconnect them? I'm no electrician, but it looks like that circuit provides system ground to the ignition. I realize that I have to shut off the ignition to get the boat out of either gear while I'm running this test.
Any other advice would be greatly appreciated!