[C320-list] Tach running high

[Jeff Hare]

Correct, the Yanmar uses a magnetic pickup on the flywheel at the back of the engine. The alternator's tach terminal is not used.This is for all the Yanmar engine used in the 320. I think there is a calibration screw on the back of the tach but can't remember for sure.  You may want to get a strobe to check the engine speed first using a dot of paint on the main engine pully.Jeff Hare
-------- Original message --------From: Joe Grande via C320-list <c320-list at lists.catalina320.com> Date: 5/31/24  12:41 AM  (GMT-05:00) To: C320-List at catalina320.com Cc: Joe Grande <joe_grande at msn.com> Subject: Re: [C320-list] Tach running high Sara, this is Joe Grande in Seattle. Assuming that Wandering Star has the Yanmar 3GM30F, I am in possession of the full service manual that I will loan you. I seem to recall that the tach reads off of the flywheel.Good luck!Joe GrandeWhisper #772, 2000joe_grande at msn.comSent from my T-Mobile 5G DeviceGet Outlook for Android<https://aka.ms/AAb9ysg>________________________________From: C320-list <c320-list-bounces at lists.catalina320.com> on behalf of Wandering Star via C320-list <c320-list at lists.catalina320.com>Sent: Thursday, May 30, 2024 7:26:53 PMTo: C320-List at catalina320.com <C320-List at catalina320.com>Cc: Wandering Star <wanderingstar951 at comcast.net>Subject: Re: [C320-list] Tach running highI’ve had this happen in two separate instances. The first is that the tach started bouncing around and that was a signal to me that the alternator belt was wearing out and not tight enough.  The tach could not get a good read.  The second is that the tach remembers the last RPM based upon some sort of a relay. I wish I knew the proper terms, but I don’t. The needle on my tack will often times sit higher at rest because that’s what the gauge remembers based upon the last relay.  I’m looking forward to the multitude of you who will respond and adequately explain what I am trying to say.   :<Sara2000/#707> On May 30, 2024, at 7:20 PM, Jeff Smith via C320-list <c320-list at lists.catalina320.com> wrote:>> I don’t know if this helps, but my non-functioning tach was the first sign> that my alternator was going bad/was bad. Or, I should say, first sign I> noticed. Since we were day sailing a lot, we were not relying on the alt to> charge the batteries. It wasn’t until we stayed overnight in the hook that> we realized the alt was not charging (hot swapped a starting battery from> another boat to get us started and home).>> You may check voltage from the back of the alt to see if it is charging. I> would expect no reading if the alt is bad,  but I have been wrong many> times before.>> FWIW,> Jeff> #121>>> On Thu, May 30, 2024 at 5:09 PM Michael Leschisin via C320-list <>> c320-list at lists.catalina320.com> wrote:>>>> Hey all,>>>> I splashed the boat a couple of weeks ago and noticed that the tachometer>> is reading a consistent 2000rpm at idle.  The engine sounds the same so I>> don’t believe the actual idle speed has changed,  just the tach.  I know>> there have been some threads in the past regarding the signal being sent>> from the alternator but has any one had a similar issue and any advise on>> where to start troubleshooting the problem?>>>> Thanks,>>>> Michael Leschisin>> Wild Blue Yonder>> C320 995