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Ran boat for last run of the season a few days ago and noticed that while at cruising rpm, about 2400, the needle on the tach was jumping around a lot between 2200 and 2400. later when I was running at 1200 rpm or so, no fluctuation. Is first thought an electrical proplem with a contact? Motor is W58 and there was no noticeable change in the sounds coming from the engine. Sounded and ran smoothe.
Any suggestions from the group?
Rodd Leeds
Windseeker
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Could be a bad connection somewhere between alternator and tach. The tach is electronic, actually measures frequency of AC from alternator before it is rectified to DC to charge batteries. If the batteries are at full charge, regulator shuts down the alternator. My tach actually drops to zero if the batteries are full as the solar panels dominate. It could be that the regulator cuts in and out with engine running but some load on the batteries. This would cause the tach to flicker a bit.
Quent -
Unless you have a yanmar, your engine runs the tach off the alternator. If your battery gets fully topped off, your regulator will turn off and stop driving your tack for short periods. If you have no other load on your batteries such as lights or an auto-pilot, the tach might turn off for several seconds. With a light load, it might turn off for less than a second and cause your tach to jump around. Hope this helps.
Regards
Rich
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My tach doesn’t register until the belt gets warm. You may have a slipping
problem. Actually, it doesn’t register until the charge voltage gets over
about 13.3. Then it’s fine. Don’t ask me why. It’s been a thorn in my
side since I’ve bought the boat.Bob
On Sun, Oct 21, 2012 at 8:35 PM, wrote:
Quote:Unless you have a yanmar, your engine runs the tach off the alternator.
If your battery gets fully topped off, your regulator will turn off and
stop driving your tack for short periods. If you have no other load on
your batteries such as lights or an auto-pilot, the tach might turn off for
several seconds. With a light load, it might turn off for less than a
second and cause your tach to jump around. Hope this helps.Regards
Rich
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Nope, standard alternator. It’s done it since the boat was new to me.
Bob
I’m not being terse. This is from my mobile.
On Oct 22, 2012 7:08 AM, “quent” wrote:Bob-
Do you have a voltage regulator external to the alternator? If so, some
of them delay charging to allow the engine to build up oil pressure, then
ranp up to full charge. My Balmar does this. It is a good thing.
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thanks for the input gents! I have never had a problem with the tach
before- I do have an external voltage reg, but tach always ran steady and
constant no matter what the RPM. This is the first time I noticed it
jumping up and down within the 200 rpm range. Again, the engine didn’t
seem to be running rough. Next day at 1200-1500 while warming my engine
for the oil change there was no fluctuation in rpm. guess I’ll have to wait
till next season!Rodd
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The other thing it can be is a loose belt for the alternator. It should
fluctuate cold and then be steady warm.Bob
On Mon, Oct 22, 2012 at 8:19 AM, Rodd Leeds wrote:
Quote:thanks for the input gents! I have never had a problem with the tach
before- I do have an external voltage reg, but tach always ran steady and
constant no matter what the RPM. This is the first time I noticed it
jumping up and down within the 200 rpm range. Again, the engine didn’t
seem to be running rough. Next day at 1200-1500 while warming my engine
for the oil change there was no fluctuation in rpm. guess I’ll have to
wait till next season!Rodd
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