Pulsating engine or outdrive??

[mesajeeper]

1987 Mercuiser 5.7 with Alpha 1 Gen 1 outdrive. When at low speeds or idle, it seems that the engine is constantly pulsating although I don't see a change in rpm's on the tach. Any ideas on what the cause of this could be?

This was our first trip out after our newly rebuilt outdrive, upper and lower. In addition, we have replaced the alternator, lower shift cable and all bellows since we purchased the boat 5 weeks ago. I mention these just in case they could play a roll in the pulsating. This whole boat endevor is getting expensive

 

[mesajeeper]

Re: Pulsating engine or outdrive??

Any ideas on this guys?

 

[wire2]

Re: Pulsating engine or outdrive??

Is it sluggish at speed?
It sounds like you might have 1 cylinder not firing. Pull the plug wires 1 at a time with the engine idling. The engine will stumble. If you pull one that makes no difference, that's the dead one. Could be a bad plug, wire, or dist cap.

 

[mesajeeper]

Re: Pulsating engine or outdrive??

Is it sluggish at speed?

No, the power seems fine. It doesn't seem like a miss to me. That's why I'm wondering if the issue could be in the new outdrive. Is there something that could cause this in the outdrive?

 

[wire2]

Re: Pulsating engine or outdrive??

Is it strictly a pulsing sound, or can you feel a vibration too?
Without actually hearing it, I can only speculate. One thought is that the ignition timing is not steady. Do you have access to a timing light to check?

 

[mesajeeper]

Re: Pulsating engine or outdrive??

Is it strictly a pulsing sound, or can you feel a vibration too?
Without actually hearing it, I can only speculate. One thought is that the ignition timing is not steady. Do you have access to a timing light to check?

I can only hear it, I do not feel it nor do I feel any vibration. I will try and make it to the lake this week and maybe record a short video so that you can hear it. Thanks for the replies.