Tach all over the place

[Freezebear]

Didn't know whether to post this here or in the lectronics forum. I have a '92 60HP Johnson Tracker. The tach is about 8 months old and has only been out about every other weekend. The problem started yesterday while going out to camp with a FULLY loaded boat. The gauge was showing 6000 Rpm's but I was going about 10MPH slower than I usually do at that speed. After getting to camp and unloading, I went back out to find tach reading OK. Then on the way in it started reading high again. At full throttle it was reading 8000 RPM! Got back to camp and checked all wiring and selector switch setting on back of the gauge. All OK. Then took boat out all day today and was reading OK. What could be wrong here? Bad tach? It's fairly new. Bad sending unit or something with the stator coils? My alternator output is OK according to gauge. I hate intermittent problems that act like this.

 

[Freezebear]

Re: Tach all over the place

 

[rickdb1boat]

Re: Tach all over the place

Could be an indication that the prop hub is slipping and causing the high RPM's and slow speed with a load on. Then again, you said it has been fine lately, so that may rule that out. I would try to find a known good tach and try it with that with a load on and see how it reacts. The speed thing and high RPM's leads me to believe there is another problem, though. Check the prop hub by making a mark on the the prop hub and prop, then see if the marks line up after you run it. Try several hard starts from dead stop.

 

[Freezebear]

Re: Tach all over the place

I really don't think its the hub because it was reading high RPM's (3000) at idle when I know it was idling at it's usual 900 in Neautral. I revved it up one time and watched as it 'Reset' itself and the needle went down to 900 and all was good again. Exactly how does the tach get its signal? If I could understand that it would help me a great deal in pinpointing the problem.

 

[sgcheek]

Re: Tach all over the place

Corroded wire connections will cause high resistance in your wiring, which in turn can cause erratic tach readings. I have had to carefully pry off the bezel and take apart my tach before to clean the inside connection of the wire terminal stud which you connect your wire to on the outside. Try cleaning all related connections very well first.

 

[DJ]

Re: Tach all over the place

Poor connections or a tach gone bad. It happens.

 

[fuzzeywiggler]

Re: Tach all over the place

Problems like this can be a real pain. You said you checked the wiring Check every inch of it again! Look all over the motor too for anything loose or anything that might be shorting out. Thats the first thing to do. It might not show up, problems like this can happen in cars to and they can seem to "fix themselves" if it keeps continuing consider a new tach

Fuzzey

 

[Gary H NC]

Re: Tach all over the place

Could it be a bad rectifier? My tach was working off and on last year and reading kind of strange.I then found out it was not charging the battery either.Replaced the rectifier and have had no more problems.

 

[seafox 257]

Re: Tach all over the place

I just had my boat in for other reasons but on the port side motor the tach is acting all crazy it will go to 8000-0 like the engine died but it is still running so I thought i just needed a new tach so I didnt even mention it to the service manager. Well when I picked my boat up he mentioned the tach problem to me he said an erratic tach is a sign of a power pack going bad but they cant tell until it goes out. so next week it is going in to get my engines tuned up for the season I am going to see if they have another tach they can hook up and see if maybe mine is bad. but maybe that could be your problem also

 

[seafox 257]

Re: Tach all over the place

just noticed this post was from 2004!

 

[Gary H NC]

Re: Tach all over the place

just noticed this post was from 2004!

GEEZE!!!! LOL!!!!