Yanmar rattle

[leefromcanada]

6 weeks ago, I bought a 1987 Mirage 29. It has a 2011 Yanmar 18 hp diesel. even though I am new to the onboard diesel world, the motor runs powerfully and reliably. however, I have a concern. Frequently, when i start the engine, the boat rattles like crazy until I mess with the throttle and it begins to idle peacefully. ive looked carefully and dont see any obvious loose bolts. any ideas?

[Sailmonkey]

It's a two cylinder diesel on soft rubber mounts. It will move wildly at idle, especially cold.

Best advice is to start with a slightly advanced throttle and stay there until you're ready to use the engine.

[JimsCAL]

How are you starting the engine? Most Yanmars do not have a glow plug and the recommendation is to start with the throttle advanced. Once it starts, you bring it down to a fast idle until it warms up a bit. I suspect the noise you are hearing is a cold engine shaking at low idle.

[krafthaus]

Hi Lee,

You mention you've checked and there are no loose bolts, but might be worth carefully checking the rubber motor mounts as well. These can sometimes crack through.

If this is only a problem when the engine is cold, then it might just be that it runs rough til it warms up.

Good luck.

[leefromcanada]

I usually start the engine throttled slightly (but not in gear). sometimes it starts cleanly. other times rattles the entire boat. in those times, I need to throttle higher before the shaking stops, then I can throttle back to neutral.

[a64pilot]

Sounds like normal cold Diesel clatter to me.
It will get worse this Winter if that is what it is.

[shakey doug]

Dr Google: Critical Speed Definition.