Westerbeke 40 Idle RPM

[brian chalk]

Is there a recommended idle RPM on the Westerbeke 40? I have gone through all the Westerbeke manuals on my boat and can't find any mention of it.

[S/V Deo Volente]

I believe it should be 625/650.

[SVJourney]

I would be careful with that number unless you know that your tach has been calibrated.  I just set mine to where I liked the sound of how it ran.  I just don't think you should force the engine to idle at a certain RPM from a book if it doesn't run well there.

[S/V Deo Volente]

Page 7 of the manual shows 750 - 1000 rpm. Yes it would be good to have a way of checking this. Borg Warner specifies at least 650 rpm in gear for the velvet drive to avoid gear rattle.
http://www.sailingseadragon.com/Manuals/westerbeke4-108.pdf

[Della and Dave]

There is a way to check the accuracy of you tac fairly easily.  You can use a reference prop tac that relies on the strobe effect and an optical sensor.  Aircraft mechanics that work on prop planes use these all the time.   You might have to paint a white line on something that spins with the engine, or through a known gear reduction like the velvet drive.  You can see what one looks like at

http://www.aircraftspruce.com/catalog/topages/trutach.php

[brian chalk]

I appreciate the responses. I have seen that Operators Manual at Garner's Sailing Sea Dragon website, and elsewhere on the internet. I always wondered if the 40NA was the same as my W40? After looking at the manual more closely I see that it is, even though Westerbeke lists the two models separately on the "model history" portion of their website.

Anyway, have set my idle speed to around 750 rpm (as measured by my old and probably unreliable tach) which "seems" about right.

[PeteW]

You can get a free Strobe Light Optical Tachometer app for your IPhone. With that and a piece of reflective  tape on the drive shaft and you call calibrate the tachometer.

Since I upgraded my alternator controller to a Mark Gasser smart controller I'm able to charge batteries at a much lower RPM. I have a green LED charge indicator lights for each bank (on the Pro split R)  and I set my idle so those lights are on. I'm guessing that to be around 800 RPM.

If you have a Borg Warner Velvet Drive there is a minimum RPM that keeps the hydraulic pressure at a safe level in in the gear box. If the hydraulic pump stalls and you loose hydraulic pressure while the motor is running it will severely damage those twin disc type design gearboxes. Doesn't matter if its in gear or in neutral.

Pete

[Della and Dave]

Cool, I didn't know there was an App for that:-).