4.3 shuts down at 3200 rpm

[Jcanine626]

Working on a 1989 Regal Boat 4.3 v6 merc.Alpha 1 outdrive . Engine starts and idles fine took out to lake got up to about 3200 rpm boat was on plane and then motor just shut down like you turned the key off. Engine will start right back up and idle all day long . This was a summer project. Put new floor in it. While repairing I took gas tank out and made sure it was clean as well as cleaned carb. I don't think it's a fuel problem . Would the coil be breaking down under load ? Or is this a shift interupt switch problem?

 

[Scott Danforth]

Its not the coil. Its never the coil Check for loose connections. Follow the Thunderbolt ignition troubleshooting guide

 

[Jcanine626]

I understand loose connections I'm an industrial electrician. I started boat at dock and use the throttle control with out drive engaged and wiggled wires on ignition switch and nothing happend boat stayed running . Got home and looked at connections on ignition control module and distributor everything was connected . I will look at the thunderbolt troubleshooting. Thanks for the info

 

[alldodge]

Look inside the distributor at the sensor module. New modules have an additional ground wire added to stop this kind of thing. Not saying its the issue, its just well know to be a possibility.

Then 10 pin engine harness connector
The lanyard kill switch

 

[Jcanine626]

I took that sensor out and it has three wires on it one going to ground. There is no kill switch up at the helm that I can see anywhere or on the throttle arm . I tried wiggling the main plug while running and nothing happend. Thanks for the info

 

[achris]

Mechanical fuel pump or electric?
Can you post the engine serial number.

 

[Jcanine626]

Mechanical fuel pump. Engine # OC 620050

 

[achris]

You need to determine if it's shutting down due to fuel loss or spark loss. Put a timing light on one of the plug leads and go for a run. As it's dying, look at the light. Still flashing means fuel, no flashing means spark. And watch your instruments. If they go out it's electrical.

 

[Jcanine626]

I'm pretty sure it's not a fuel issue because it does not spot and sputter like it's out of gas it shuts down completely and then can start right back up. I'm thinking my shift interupt cables are out of adjustment causing the shutdown soon as you put it back in neutral it fires right back up

 

[alldodge]

Assuming it has a TB-IV distributor.
Start the motor, get it to where you can run the boat up to speed. Stop and disconnect the shift interrupter, and then take it up to speed and rpm. If it does not die then its the shift interrupter.

Need to reconnect the wires in order to shift out of gear

 

[Jcanine626]

Ok thanks I'll try that this weekend