I would very much appreciate some advice from all you guys who understand Mercruiser 5.7L V8s better than I do. Thsi is the problem:
We are about 15 engine hours into the season and she was fully serviced by a good dealer before the season started.
The last couple of sessions, the boat has started fine off the trailer, run half a dozen sets and then the motor has started to faulter. It will lose power totally and sometimes can be nursed back but sometimes stops altogether. She then won't start without a lot of work of the starter and the gears being disengaged.
When she does start (always with lots of throttle) the chances are she will die again when returned to neutral.
Other times she will faulter and stop when we go to neutral. Again it can be tough getting her going again.
Also, several times today, she idled happily at the dock for 5 minutes and then just stumbled and stopped.
To try and clear things out, I did a couple of 45mph runs and she ran sweetly without problem. Drop back to 24mph and she would hesitate again.
By the way, she was fuelled with clean gas through a filter. And there is a water separating filter installed. I'm wondering if replacing this was missed at the service.
FInal point, the Thunderbolt ignition failedlast season and was replaced with a conventional non-electronic points-type distributor.
Thank you in advance for any advice offered. Some pics of the engine are attached in case it matters exactly which type it its.
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