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Author Topic:   Tachometer Shows 700-RPM At Rest: Correlation to Failure of Hour Meter
oneengland posted 02-05-2010 05:07 PM ET (US)   Profile for oneengland   Send Email to oneengland  
I have a 1999 Mercury OptiMax 225-HP bolted to a 1999 [Boston Whaler] 20-foot Ventura. The hours on the clock [possibly means the engine hour meter] have remained the same for the last six months. Clearly it is broken. The other day I noticed my [tachometer] was set at around 700-RPM when the engine was off. Could this be a indication of actual hours? Or, does this engine not have this feature? Shot in the dark? Many thanks in advance
510racer posted 02-05-2010 05:23 PM ET (US)     Profile for 510racer    
Most analog tachometers display the engine speed that the engine was at when the key was turned off. Yours was probably idling at 700 when you turned it off.
Mambo Minnow posted 02-05-2010 08:00 PM ET (US)     Profile for Mambo Minnow  Send Email to Mambo Minnow     
An authorized Mercury service center can tell you hours run across the RPM band from the ECC computer memory.
jimh posted 02-05-2010 10:41 PM ET (US)     Profile for jimh  Send Email to jimh     
Most tachometers have a "zero" or quiescent current position that corresponds to a dial indication of about 700 RPM. This has nothing to do with the engine running time in hours.
Chuck Tribolet posted 02-06-2010 08:40 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Hour meters are pretty simple. I'd be thinking that a wire
has come disconnected somewhere.


Tohsgib posted 02-06-2010 09:38 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
If wire is not lose or bad, meter is bad. Easy enough to check. There are only 2 tabs on the back besides maybe a light, positive & negative. Connect a 12V battery to it and wait an hour to see if it moves. Some have minute or 1/10 increments as well so you might not have to wait an hour.
Tohsgib posted 02-06-2010 09:52 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
PS--turn key to "on" and rpm's should zero out.
jimh posted 02-06-2010 12:19 PM ET (US)     Profile for jimh  Send Email to jimh     
I do not think the author is soliciting advice on how to make a repair to his small boat electrical system. As I read the original article, he is simply seeking a clarification if the dial indicator position of an engine tachometer when the engine is turned off shows the number of hours of running time on the engine. I make this inference because I cannot find any other meaning for the term "clock" that makes sense. I do not believe anyone thinks a tachometer shows time of day when it is turned off.

I don't see the need for much further discussion on how a tachometer's dial pointer could be interpreted as showing either time of day [and I was going to close the discussion, when, much to my surprise, the topic of a SUZUKI motor came up which does use the tachometer to convey certain engine information].

Tom W Clark posted 02-06-2010 12:27 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
I seem to have some vague recollection of some tachometer that would use the engine-off position of the tachometer needle to indicate he accumulated engine hours on an outboard motor.

What band of motor am I thinking of?

510racer posted 02-06-2010 12:48 PM ET (US)     Profile for 510racer    
I searched and found that it seems some suzuki's do have this feature, not sure which models specifically.

Here is a piece of info I found:

"The needle indicates hours, and if the check engine light (I think) flashes, that indicates a 500 hour increment. So if the needle is on "3" and the light does not flash, then it has 300 hours. If the needle is on "3" and the light flashes once, that means there are 800 hours, etc."

number9 posted 02-06-2010 05:54 PM ET (US)     Profile for number9  Send Email to number9     
Also remember reading, think it was SmartCraft tach, that would give hours using the RPM indication. Don't recall if it was with power on or off and engine not running.
jimh posted 02-06-2010 09:43 PM ET (US)     Profile for jimh  Send Email to jimh     
You guys are pulling my leg, right?
Tohsgib posted 02-07-2010 08:45 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Yes my Suzukis do have that feature. Unfortunately you kinda need the manual in front of you to decifer the blinks and needle position. How it works(just for Jimh): needle Rev limit flash flash flash flash flash
etc flash
550hrs...500rpm...1 flash
560hrs...600rpm...1 flash
600hrs...1000rpm...1 flash
700hrs...2000rpm...1 flash

1040hrs...5400rpm...1 flash
1050hrs...500rpm...2 flash

1540hrs...5400rpm...2 flash
1550hrs...500rpm...3 flash

2030hrs...5300rpm...3 flash
2040+hrs...5400rpm...3 flash

*1 flash of the rev-limiter light corresponds to 500hours.
Needle moves in 10 hour increments.

The tach also tells you what engine code it throws and when to change your oil by flashing certain lights like morse code or maybe Close Encounters of a Third Kind.

jimh posted 02-07-2010 02:07 PM ET (US)     Profile for jimh  Send Email to jimh     
Can you tell me how the tachometer does all that when the key is turned to OFF? And does it keep doing it all the time the key in in OFF?
jimh posted 02-07-2010 03:33 PM ET (US)     Profile for jimh  Send Email to jimh     
[Moved to SMALL BOAT ELECTRICAL, where such topics as these are discussed.]
Ridge Runner posted 02-09-2010 07:07 AM ET (US)     Profile for Ridge Runner  Send Email to Ridge Runner     
The tach that Nick is refering to is Suzuki part number 34200-93J11 Tachometer with monitor guage(white face) cost is about $160. The link will take you to the 2008 accessory guide. On page 18 of the guide is the tach.
jimh posted 02-09-2010 08:41 AM ET (US)     Profile for jimh  Send Email to jimh     
The way you are supposed to interpret the engine hours with this complicated method of observation of flashing lights on the tachometer reminds me of how on my 1993 FORD sedan I could similarly get the check engine light to flash in a complicated pattern, and how, by carefully counting the flashes and resorting to a code book, I could interpret them to deduce the meaning of the signal the check engine light was sending: all very obscure and essentially of extremely limited usefulness.

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