Proper Idle Speed/Tach issue

bdaball

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New Member here.
2019 S-20, Yamaha F70, 40 hrs.

Boat runs sweet, idles nice, top end is fine.
Tach used to read approx 6,000 rpm at top end. Not sure what idle should be, (??)
I just noticed yesterday it was reading beyond 7,000 wide open and tach stay at about 1,100-1,200 on idle. Tach remains at 1,100-1,200 when key is turned off. When you turn the key back on it zeros out. ??? Is this normal ??
I never paid attention before but with trim/motor "down", should trim gauge return to "up" when you turn the key off ?? Sorry, new-bee question.

Please and thanks
 
Typically the tach's have multiple switches at the back of the tach that line up with what your motor configuration has. 2 , 3 pole, etc. Its the black circle that you adjust to your specific outboard
Have you check that?

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Thank you. Yes, I have read that in other places. What is confusing me is that top end was showing around 6,000rpm at top end and now all of a sudden it is reading 7,000/at the very end of the dial. Everything sounds as it should during idle and running. Should I adjust the tach down and if so down to what at idle? No concern about it staying at 1150/1200 after key is off then dropping to zero when key is turned back on ?

The other question please, should the trim return to "up" when the key if off? Sorry, new-bee and don't remember if it ha been like that since I've had it. Only have 40 hours on the gauge.
 
New Member here.
2019 S-20, Yamaha F70, 40 hrs.

Boat runs sweet, idles nice, top end is fine.
Tach used to read approx 6,000 rpm at top end. Not sure what idle should be, (??)
I just noticed yesterday it was reading beyond 7,000 wide open and tach stay at about 1,100-1,200 on idle. Tach remains at 1,100-1,200 when key is turned off. When you turn the key back on it zeros out. ??? Is this normal ??
I never paid attention before but with trim/motor "down", should trim gauge return to "up" when you turn the key off ?? Sorry, new-bee question.

Please and thanks

I have the same boat & motor, except it’s a 2014. The tach goes to 1200 and trim gauge goes all the way up when the key is turned off. Always has. As far as the accuracy of the tach, it’s rarely correct. Something is probably loose but I haven’t been able to trace it down. I quit trying and hooked the motor up to the Garmin for the RPM’s and other info. The NMEA setup was pretty easy to do. If I could take that center gauge cluster out and hook up another Garmin screen there to display digital gauges, I would. But I’m not that knowledgeable. Idle is 600 - 700rpm. The WOT on the motor is 6400 rpm which I get 17 mph by gps. I have the K11 prop on it. The rev limiter kicks in at 6400, so that’s all your going to get out of it.
 
That is what I suspected. My previous Sweetwater had the same issue only in the opposite. I may try calibrating once to see if it stays. I was not sure at what to set idle. I guess I'll shoot for 650. (?)

Seems odd to me but maybe as a newbee I'm taking too much for granted that gauges are not more accurate or long lasting. I guess I'm hoping for a little better luck with the hour meter.
 
UPDATE: So just before boat was taken out for the winter I did adjust the idle reading on the tach down to 600. Took one final run across the lake. Still runs fine but now top end reads 4800+_. WTH ? Grrrrrr........? I guess I have all winter to think this issue out. Any ideas ??
 
 
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