Running over max RPMS

[Ken Honeycutt]

Last summer I got into a squirrly docking situation with high cross winds in a crowded marina. Make a long story short - in order to avoid a collision with a high dollar powerboat, I cranked up the diesel somewhere around 4000 RPM for a short period of time in reverse (Max RPM of 3600 - I wasn't watching the tach until after I knew I'd missed the other boat). I'm assuming this wouldn't damage the engine since it was for a short period of time but I'm wondering now at what RPM past maximum is safe to run and for how long (BTW I saw another sailboat get blown into several other boats trying to dock in the same general area so I didn't feel too badly about almost colliding with the power boat).

 

[Maine Sail]

Last summer I got into a squirrly docking situation with high cross winds in a crowded marina. Make a long story short - in order to avoid a collision with a high dollar powerboat, I cranked up the diesel somewhere around 4000 RPM for a short period of time in reverse (Max RPM of 3600 - I wasn't watching the tach until after I knew I'd missed the other boat). I'm assuming this wouldn't damage the engine since it was for a short period of time but I'm wondering now at what RPM past maximum is safe to run and for how long (BTW I saw another sailboat get blown into several other boats trying to dock in the same general area so I didn't feel too badly about almost colliding with the power boat).

Ken,

Your engine should be rev limited or governed to quite close to Max RPM. You may want to double check your tach with a digital photo tachometer..

 

[Ross]

I have heard that runaway engines take quite a while to self distruct. But you weren't running the engine in reverse you had the transmission in reverse. As Mainesail said get the tach and governor checked out.

 

[Ken Honeycutt]

I have heard that runaway engines take quite a while to self distruct. But you weren't running the engine in reverse you had the transmission in reverse. As Mainesail said get the tach and governor checked out.

Right - I should have said I had the transmission in reverse. My thinking was that max RPM was the MAX RPM that the engine should be run for normal operations but that the governer may be set higher.

 

[Scott B]

Ken, IIRC the 3YM30 max is 3800? there is a limiter built-in. I regularly push mine to WOT for several minutes to clear the carbon as per the Yanmar manual.

 

[druid]

Most diesels have a "Max RPM" (which is what that governor is set for) and a "Max Continuous" which is the most it should be run at for long periods. Try running the engine up in neutral - does it go beyond 3600? Then either the tach is wrong or the governor is screwed up. I suspect the former.

druid

 

[Ross]

All diesel engines are governed. Advancing the throttle adjusts the injector pump to supply the fuel needed to reach the desired rpm setting. You should be able to shove the throttle wide open with no load and have the engine top out at the specified RPM.

 

[Ken Honeycutt]

Thanks for the responses..per Mains' suggestion I'm going to invest in a photo tach (about $25 off ebay)..Per Scotts' reply and based on my cruising speed that seems lower then it should be, my tach may be off a couple hundred RPM.