Replaced Rectifier now Tachometer off by 1k Rpm

[Overtime33]

Hi everyone, searched for this but haven't found the answer exactly. Last summer my battery stopped charging on my 2004 Yamaha 115TXRC. Did some searching online, suggested that it could be the rectifier or stator. Eventually bought a new rectifier from iboats best price I could find. Now shes charging again 13.5-14 volts Only problem is now my tachometer is reading 7k+ at wot! Boat goes the same speed and sounds the same so pretty sure engine isn't going that fast, it's even off at idle used to be 800 rpm at idle now says 1500 roughly. On the back of the tachometer there is a selector 1 - 7 i think. Right now it's below 1 is this setting right? I read that most boats are set to 4. Is this how many cylinders in your engine? Also wondering what might have caused the rectifier to go bad on a motor with around 100 hrs? Does this mean my stator is good? I checked the wiring to the stator and it doesn't seem melted or burnt in anyway. My nearest boat shop closed a couple years ago kinda a newbie at this stuff appreciate any input thanks in advance. Overtime33

 

[twisterlodge]

Re: Replaced Rectifier now Tachometer off by 1k Rpm

yes the numbers on the back of the tach. refer to the number of cylinders. was your replacement rectifier the same part? (yamaha part no)
im sort of supprized your charging system was corrected by replac ing a rectifier. i would normanlly susspect a voltage reg. to be faulty.?

 

[99yam40]

Re: Replaced Rectifier now Tachometer off by 1k Rpm

Depends on Tach.
Most that I have seen are set for # of pulses , but some are # of cylinders.

 

[Overtime33]

Re: Replaced Rectifier now Tachometer off by 1k Rpm

twisterlodge:
The part # on the old rectifier was SH678B-13 then below part # was 3.8.1. The new rectifier # is SH678QA and below that part # is 9.1 151 They were identical physically though. I first noticed the engine wasn't charging while on a fishing trip up north last summer. Went to the Boat Shop up there and the rectifier was one of there suggestions. They did warn me not to run the engine if the rectifier was faulty as it could start a fire. We finished are trip and I did run it some what but kept an eye on it to see if it was heating up which it wasn't. Could the voltage regulator be bad? I get a consistent 13.5 - 14 volts with a digital multimeter to the battery while engines running.

99yam40:
The tach in the boat is a Faris brand and I am unable to find any documentation on it. Was hoping something came with my boat when I bought it but found zilch. I keep all my manuals for just about everything I own, I may have a manual hording problem lol. I've never changed the dial on the tach before. I bought my boat new so I believe thats how it was set before. I take it I won't hurt anything by setting it to 4 and seeing if that helps? Since it was last summer I can't remember if my tach was working or not, I don't think it was working at all. I read somewhere online that the dial contact can corrode and to turn it all the way one way and then back to make sure the dial is making contact. Should I ditch this Analog tach and upgrade to digital? Hate to buy parts I don't need but really like having a tach. Btw thanks for the quick response, Overtime33

 

[99yam40]

Re: Replaced Rectifier now Tachometer off by 1k Rpm

http://faria-instruments.com/site_manuals/IS0100_Tachometers.pdf

Check the Faria web site for info and manuals.
I take it you just misspelled the brand name.

http://faria-instruments.com/site_manuals/IS0012u.pdf

This gives more info on settings for different motors

 

[Overtime33]

Re: Replaced Rectifier now Tachometer off by 1k Rpm

99yam40:
Yah I did a double take on the tach gauge it is a faria brand gauge Thanks for the links. Says to turn the selector switch on the back of the tachometer to the correct position to match the number of poles in the alternator. I didn't see my motor in there example however they did have a 115 Suzuki which said it was a 12 pole which would be 5 on the selector. I will call them tomorrow and confirm. From day one the tachometer light would go in and out on me all the time this is only when nav lights are on. Of course when I would take it to the dealer it would work fine for them. I noticed that when I move the gauge slightly the light will go on or off. I also noticed that the negative pole on the tach was loose so I tightend the nut which firmed up the bolt but it didn't fix the loose connection. I switched the light bulb out with the speedometer bulb which I have never had a problem with, the tach light still cuts in and out so it's not the bulb. The mechanic up north told me that odds are something may have caused my rectifier to go bad such as poor ground or a short. Is my tach a possible canidate? It seems the tach looses ground with the slightest touch, the tach has always worked though the light was the only problem before it was off. Maybe I'm over thinking this one just don't want to spend another $140 on another rectifier down the road. I'm leaning towards a new tach.

 

[99yam40]

Re: Replaced Rectifier now Tachometer off by 1k Rpm

I would think he was talking about a battery ground or main motor ground connection.
Tach light ground should be the same as the tach signal ground , only one ground connection or does yours have more ,so if that does not mess up then I would tend to think it has to be the light power connection internal or external that is going bad.

I noticed the listing for Yamaha C75-C150, P75-P200 -- 12 pole in the link maybe that covers you motor

 

[Overtime33]

Re: Replaced Rectifier now Tachometer off by 1k Rpm

Called Faria today they confirmed that it is a 12 pole therefore I set the selector on the back of the tach to 5. Which is really odd since it was below 1 originally, when I told the guy a Faria that he said that it must be showing to high of an rpm. Also spoke to him about the negative pole on the tach that anytime I slightly wiggle it the nav light cuts out. He suggested tightening the first nut on the negative pole. Which I have already, did tell him I didn't want to over tighten the nut. He said thats good since it would damage the tachs internals. He suggested keeping an eye on the pole itself to make sure it doesn't turn if it does that would be too tight. I have always had the light problem with the tach since I bought the boat new. He said if it's still not working after I tighten it then something is wrong with the tach and to send it in under warranty only thing is that I probably won't get it back for 4-6 weeks May just run it like this till winter & send it in then as long as it shouldn't hurt anything that is??

 

[99yam40]

Re: Replaced Rectifier now Tachometer off by 1k Rpm

Are you sure the pointer was in that direction, toward the 1 position or was it 180 degrees in the other direction toward the 5?
Seems odd that it has worked before at that setting. Maybe contacts just need to be cleaned by switching back and forth a few times

Keep us informed as to whether or not it works and what the problem was

 

[Overtime33]

Re: Replaced Rectifier now Tachometer off by 1k Rpm

All I know is all I did was replace the rectifier. Took it out for the first time and tach was off. It doesn't make any sense that it was right with the old rectifier. Plan on taking it out this weekend weather permitting will post the result on here. Thanks for the help I would still be looking for a faris tach and not a faria one haha.

 

[Overtime33]

Re: Replaced Rectifier now Tachometer off by 1k Rpm

Spent the weekend fishing on Mill Lacs lake. The tach seems accurate now, my idle rpm is 850 that seem right? Still loose the light on the tach at night but the tach is working (shined a flash light on it). If I reach up an turn the light bulb, the light will come back on sometimes. Just glad the tach is up an running. Thanks for all the help guys.

 

[rodbolt]

Re: Replaced Rectifier now Tachometer off by 1k Rpm

next time find a tech that knows.
the tach send circuit on your 115 comes from the engine ecu and has NOTHING to do with charging systems.
its not a jonnyrude nor a merc.