Don-
I’m starting a new thread, since the original was about play in a Max Prop. I’m assuming your reduction gear was inverted, and you meant 2.13:1. I’ll also assume the 2900 RPM max a calibrated number (meaning you checked your tach/RPM with an app or other measurement and it is accurate.
Here’s my thoughts:
- 2900 vs. 3000 is a relatively small difference, even if that RPM is with a clean bottom and the boat not fully loaded.
- Black smoke usually is from unburnt diesel fuel. In a new installation, where everything is “operating per spec” over-propping is often the cause.
- Unburnt fuel could have many causes though:
– Restricted airflow. The same low RPM running or not running up to operating temp that sailors often do can restrict the exhaust riser. Or it could be failing. Also, even with the Westerbeke’s simple air intake, insulation or some other blockage could be restricting it.
– Worn or otherwise poorly function injectors. They don’t work optimally forever.
– Low-quality fuel. If you unintentionally filled up with a low-quality fuel, it may have impacted the combustion.
Separately, if you’re reaching 2900 RPM, I think you’d need to demonstrate to Flexofold that you’ve eliminated other causes. They’ve probably sized thousands of props, including many Nonsuch, and from what I read before my purchase, are pretty good at it.
Dan Weinstein
Look Farther, 30C #205
East Greenwich RI