Setting Idle Speed

[Tim April IV]

Came across this bulletin from Westerbeke - Manufacturer of our M35B engine
http://www3.telus.net/Atomic_4_Eng_Serv ... ttings.htm

BULLETIN NUMBER: 7

DATE: 2004

MODEL: New Universal Diesel Engines: M3-20B, M25-XPB, M35B, M40B, M50B

SUBJECT: Idle RPM Settings to Prevent "Damper Chatter"

New Universal diesel engines have an idle specification range of 200 rpm... ie 3 cylinder engines 1,000 - 1,200 rpm / 4 cylinder engines 800 - 1,000 rpm. In most cases the idle should be adjusted to the highest spec... ie 1,200 for 3 cylinder engines and 1,000 for 4 cylinder engines, in order to ensure there is no flywheel drive damper disc "damper chatter" when the engine is run in gear with the throttle set at idle. Damper chatter gradually damages the drive damper disc springs and the marine gear splined input shaft and forward/reverse clutches.

Because idle rpm in gear is related to propeller size, even with the idle speed adjustment set to the highest rpm specification the engine should still be checked for damper chatter by engaging forward gear with the boat tied to the dock and the throttle lever pulled back against the idle stop so the engine is idling at its lowest rpm setting. If damper chatter is occurring it will be heard as a faint metallic clicking noise coming from the flywheel housing which stops when the engine rpm is raised slightly. It may be easier to hear if one end of a piece of wood (ie a section of broom handle) is held against the flywheel housing and the other end is held close to the ear (AKA a mechanic's stethoscope).

Note: The actual engine idle rpm should be determined using a portable mechanic's tachometer held against the middle of the front crankshaft pulley, not the control panel tachometer (control panel tachometers are not accurate enough to be used for testing and / or adjusting the engine governor idle and maximum speed rpm stops because they usually are not accurate at all rpm even after being calibrated / adjusted at one specific point - which is usually maximum rpm or normal cruise rpm).

[Hans Grasman]

Gee thanks Tim. Just as I am trying to get a few boats in SW Fl. together to fix our PSS systems after having received the retrofit engineering bulletin #69. Now you come up with another thing on the engine idle.
Calling my doctor today to borrow his stethoscope
Maybe we will soon receive a "damper clatter" kit in the mail
Have a great day!

[william vanwagoner]

I am in the process of setting my idle a little higher and found that the idle adjustment screw goes through a nut, presumably to lock it in place against the seat. The end of this screw serves as a stop for the throttle lever (the high speed stop is wired shut). I had to remove the screw and nut as the nut is glued to the screw with paint from the factory, and hope to replace both these parts with non-paint covered parts. One question - for those who have done this adjustment, is the nut against the seat truly enough to keep it from vibrating loose (without being stuck with paint as from the factory)? Should I put a little lock tight or something on it? Also, has anyone else replaced the idle screw and nut and where did you find them as this seems to be about the only set of parts I don't see in the Universal parts manual?

thanks,
Bill

[leigh weiss]

Bill,
For me , the lock nut is enough to ensure the screw stays put!
I repainted the work area with a spray can of paint I got from an auto parts store (light metallic blue)
About $7
I used an optical tachometer to adjust the idle. You can't rely on the gauge on the instrument panel.
Have fun.
For better access to that adjustment, I removed the engine stop lever by removing the shaft nut and washer and pulled the splined lever off the shaft.

Leigh Weiss

Brisa #155
Upper Chesapeake Bay MD.

[nybor]

Hi all.
Question. Even though I didn't TOUCH the throttle cable when I replaced the damper, I notice that when it is out of gear, I have to push the lever maybe 30 degrees before the engine rpm increases. It is as if it is not connected to the engine throttle. Also, when I push it all the way forward it springs back somewhat. I think that is a safety spring so you don't overrev the engine, but not sure. I just don't remember this situation before the damper change. (obviously i am delusional)
any ideas or comments?

thanks
dave

ps come to think about it I DID slightly adjust the transmission cable - I wonder if that affected the throttle cable up at the Pedestal?

[leigh weiss]

Dave,
The throttle and gear shift is combined into one control. The first part of the rotation of the shift handle is to engage the gear and then advance the throttle. If the throttle advances to a full speed position with the handle at its maximum, it would be that all is well. If you have further travel on the handle after Wide Open Throttle (WOT) the springiness might be the cable loading because of compression and flexing like a spring. Adjustments to the cable length might be in order to fix this problem. Try to observe the position of the cables and clamp marks around the engine connections before you make any adjustments.
I assume all was well before you changed the damper plate.

Leigh Weiss Brisa #155