Tach question - experts? - SailNet Community
 1Likes
  • 1 Post By chucklesR
 
LinkBack Thread Tools
post #1 of 10 Old 04-15-2013 Thread Starter
Senior Member
 
chucklesR's Avatar
 
Join Date: Sep 2007
Location: Pasadena Md - Magothy side
Posts: 5,979
Thanks: 10
Thanked 31 Times in 31 Posts
Rep Power: 10
     
Tach question - experts?

The installed tach on my Yanmar 44hp (type b panel) is at my shin level on the pedestal.
So I installed a new Faria tach in my Navpod where I can see it. I wired it correctly and set the adjusting knob to 127 teeth- all per my manuals, guides and such.

When I start the engine it cranks right up and shows 850 or so RPM at idle.
When I throttle up it will only go to 1600-1700 - I mean both showing on the gauge and actual RPM (you can hear it's not full speed).

A disconnect and reconnect - restart and presto - the old tach idles at 850 and throttles up to full (3600) RPM under no load.

Obviously something is wrong with my tach's settings and I need to adjust it -

But seriously - does a tach being off make it so the engine can't get up to full RPM via some sort of feedback with the alternator?

Lessons learned are opportunities earned.
chucklesR is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
Advertisement
 
post #2 of 10 Old 04-15-2013
Just another Moderator
 
Faster's Avatar
 
Join Date: Sep 2005
Location: New Westminster, BC
Posts: 16,373
Thanks: 101
Thanked 304 Times in 294 Posts
Rep Power: 10
     
Re: Tach question - experts?

If you're using a flywheel pickup sensor I don't see how that connection can have anything to do with the load on the engine.. for that matter neither should the stator output off the alternator..

Mysterious..

Ron

1984 Fast/Nicholson 345 "FastForward"

".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
Faster is offline  
Quote Quick Reply Share with Facebook
post #3 of 10 Old 04-15-2013 Thread Starter
Senior Member
 
chucklesR's Avatar
 
Join Date: Sep 2007
Location: Pasadena Md - Magothy side
Posts: 5,979
Thanks: 10
Thanked 31 Times in 31 Posts
Rep Power: 10
     
Re: Tach question - experts?

Come on, really? No body is the Fric and Frac of diesel's ?

It is a flywheel pickup. Yanmar 44 4jthe 1987.

Lessons learned are opportunities earned.
chucklesR is offline  
Quote Quick Reply Share with Facebook
post #4 of 10 Old 04-17-2013
Asleep at the wheel
 
jimgo's Avatar
 
Join Date: Sep 2011
Location: Pennsylvania
Posts: 3,014
Thanks: 71
Thanked 117 Times in 115 Posts
Rep Power: 4
 
Re: Tach question - experts?

Since you're not getting any other feedback, I'll throw in a wild conjecture. Is there an electronic governor on the engine? Could the tach that you're adding be causing funky readings on the governor?

- Jim
Home: Western Philly 'burbs
1980 Allmand 31
1975 Albacore 15


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
jimgo is offline  
Quote Quick Reply Share with Facebook
post #5 of 10 Old 04-17-2013
Senior Member
 
tommays's Avatar
 
Join Date: Sep 2008
Posts: 4,296
Thanks: 1
Thanked 30 Times in 30 Posts
Rep Power: 7
 
Re: Tach question - experts?

Unless I am missing something it is a normal mechanical fuel injection diesel without any type of electronic stuff on a more modern style ?

The tack should not have any ability to affect the engine speed unlike a gasoline motor were a tack is part of the ignition circuit and a bad unit can affect spark.

I would turn the input thing-a-mcbob that sets the tack speed and see what happens as when I put the new one on my A4 the arrow was backwards

1970 Cal 29 Sea Fever

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

1981 J24 Tangent 2930
Tommays
Northport NY


If a dirty bottom slows you down what do you think it does to your boat
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
tommays is offline  
Quote Quick Reply Share with Facebook
post #6 of 10 Old 04-17-2013
Senior Member
 
hellosailor's Avatar
 
Join Date: Apr 2006
Posts: 11,335
Thanks: 4
Thanked 129 Times in 126 Posts
Rep Power: 11
   
Re: Tach question - experts?

Chuckles, with a tach reading off the flywheel sensor, you shouldn't have any interference with engine speed.

The wires on the sensor are just counting pulses, plugging and unplugging that should make no difference in how things run but do try that to verify. Then there should be two power wires for the tach, and that should just be seen as another 12-volt device, nothing special, no way to change engine speed by plugging and unplugging them.

It sounds more like you've got some kind of accidental interaction, that the tach is pulling voltage or creating a voltage loop somehow. If you had exotic electronics it could be a magnetic interference issue but I don't think Yanmar has blessed anyone with that stuff yet.

If you fire it up with the new system, and then disconnect the sensor lead to the new tach, or the power lead to the new tach, does connecting/disconnecting either of those allow your engine rpm to go up all the way again?

Is there any chance that some of the new wiring is simply blocking your throttle cable, or something "it can't be that simple" simple?
hellosailor is offline  
Quote Quick Reply Share with Facebook
post #7 of 10 Old 04-17-2013 Thread Starter
Senior Member
 
chucklesR's Avatar
 
Join Date: Sep 2007
Location: Pasadena Md - Magothy side
Posts: 5,979
Thanks: 10
Thanked 31 Times in 31 Posts
Rep Power: 10
     
Re: Tach question - experts?

I've not gotten back to it, waiting for input.

There are four wires to the tach, +/- for 12v, sig port and sig stbd -
I took (by T'ing in) the feed for all of them to the original tach.
I did resistance checks on each wire to ensure what was what (from the T to the engine connections (center cockpit's rule).
I swap old for new by simply disconnecting and reconnecting at the new tach (remove ring connectors, put tape over the ends).
The only thing I have not done is make the signal inputs a 'twisted pair' - they are only 18 inches long coming off the T - I'll have to try that today.
It's a 1987 engine, it's not got electronic diddly squat.

All the cabling is tied up, no binding (I can see it to check, the pedestal front is removable).

I'll go puzzle it out some more today, but thanks seriously for the input.

Lessons learned are opportunities earned.
chucklesR is offline  
Quote Quick Reply Share with Facebook
post #8 of 10 Old 04-22-2013 Thread Starter
Senior Member
 
chucklesR's Avatar
 
Join Date: Sep 2007
Location: Pasadena Md - Magothy side
Posts: 5,979
Thanks: 10
Thanked 31 Times in 31 Posts
Rep Power: 10
     
Re: Tach question - experts?

It's been a long week.

It's been fixed. It was not a tach issue. More testing revealed the low RPM on the new tach was coincidental and happened (randomly) on both tach's.

The problem worked out to be the fuel shutoff solenoid not fully engaging/disengaging because it was being forced into a 320 degree loop. Apparently it had been that way for a while and my 5 hour trip on the motor bringing the boat home - as well as the sea trial - was just lucky.

Lessons learned are opportunities earned.
chucklesR is offline  
Quote Quick Reply Share with Facebook
post #9 of 10 Old 04-22-2013
Asleep at the wheel
 
jimgo's Avatar
 
Join Date: Sep 2011
Location: Pennsylvania
Posts: 3,014
Thanks: 71
Thanked 117 Times in 115 Posts
Rep Power: 4
 
Re: Tach question - experts?

Oh, good. Glad I was right! (kidding)

Glad you were able to figure it out. How is it running now?

- Jim
Home: Western Philly 'burbs
1980 Allmand 31
1975 Albacore 15


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
jimgo is offline  
Quote Quick Reply Share with Facebook
post #10 of 10 Old 04-22-2013 Thread Starter
Senior Member
 
chucklesR's Avatar
 
Join Date: Sep 2007
Location: Pasadena Md - Magothy side
Posts: 5,979
Thanks: 10
Thanked 31 Times in 31 Posts
Rep Power: 10
     
Re: Tach question - experts?

It's absolutely perfect now. Thanks for asking and hope your's gets well soon.
jimgo likes this.

Lessons learned are opportunities earned.
chucklesR is offline  
Quote Quick Reply Share with Facebook
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Tach PAULCR1 Gear & Maintenance 9 02-11-2013 11:01 AM
Replacing the Tach; Universal 5411 "Tiny Tach" jrhamp Diesel 3 10-23-2012 12:26 AM
Balmar/Max Charge question for the experts GeorgeDog Electrical Systems 4 07-20-2010 09:15 AM
desiel tach: Tiny-tach dreuge Diesel 5 04-30-2010 11:04 AM
Small outboard motor question for the maintenance experts. Northbeach Gear & Maintenance 7 07-19-2008 12:48 AM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome