38 engine noise

[norbszczurek]

While under sail we are experiencing noise that almost sounds like the engine is still running. Upon further investigation it appears that the prop shaft may be spinning, this occurs both in neutral and forward gears with the engine off and seems to stop when put in reverse. Any help or ideas would be greatly appreciated.

 

[dparilla]

First, don't worry, then just sail in reverse. Many props will spin when left in neutral or forward. Putting it in reverse after shutdown has the effect of locking the shaft. A spinning prop can cause quite a bit of drag and noise/vibration, but in neutral, it should not cause any harm. Some owners manuals recommend neutral or reverse, but we have always locked ours in reverse. Just be sure to put it in neutral before starting the engine.

 

[Ralph Johnstone]

You Should Find Out ....................

...................... the make of your transmission before deciding where to leave it when under sail.

The attached may not apply to your set up but it shows the problems that can arise from not knowing which gear to leave it in.

 

[Stu Jackson]

If you do a search here on "transmission position" you will read for years! This is a recurring question.

Yanmar engines - read what Ralph posted

Universal engines with Hurth transmissions - reverse or neutral, never forward.

 

[Alan Gomes]

First, don't worry, then just sail in reverse. Many props will spin when left in neutral or forward. Putting it in reverse after shutdown has the effect of locking the shaft. A spinning prop can cause quite a bit of drag and noise/vibration, but in neutral, it should not cause any harm. Some owners manuals recommend neutral or reverse, but we have always locked ours in reverse. Just be sure to put it in neutral before starting the engine.

MaineSail did an experiment in which he showed the freewheeling prop as having less drag than when fixed--at least under the configuration in which he did the test.

 

[Claygr]

Note that the Yanmar advisory only applies if you have a fixed prop. If you have a folding prop, the transmission needs to be in reverse for the blades to close and then it can be moved to neutral (or left in reverse).