Cruisers Forum

Join CruisersForum Today

Thread Tools Rate Thread Display Modes
Old 23-05-2011, 14:58   #1
Registered User

Join Date: Mar 2007
Location: New Orleans
Boat: Gulfstar 37 - Perseverence
Posts: 66
Perkins 4108 Tachometer Reading High

I have a strange problem that has cropped up. I've owned this boat for several years so I am very familiar with the engine and systems. I went for an overnight cruise the other day, tied up at the end of the day, and hooked up to a shoreside power provide by a town on the water. Tachometer was working normally at this point.

The next morning, I started the boat and the tachometer is reading high - I mean really high, by about 900-1000 rpm. You could tell by the sound, but as I said I know this boat and the rpm it takes to make my cruising speed of 7 knots under power, and it was reading about 1000 rpm high.

The tach drops to zero when the engine is off, and I have not worked on anything or fiddled with the alternator to cause this. Nothing is slipping and the RPM is really not as high as it is reading - I've verified this with a phototach.

Anyone got any ideas as to what could cause this, and more importantly, what could fix it? The boat is a 1979 Gulfstar 37 - engine a 1991 replacement, no problems prior to this, as far as I can tell the gauges are the orginal that came with the boat....

I've checked the forum archives, and don't seem to see anyone that has had this problem....

Old boats, what we buy when we think we have too much time on our hands......
jlogan is offline   Reply With Quote
Old 23-05-2011, 15:36   #2
Registered User
Bill S's Avatar

Join Date: Mar 2010
Location: Full time cruising
Boat: Southern Cross 39 - Nemo
Posts: 37
Re: Perkins 4108 Tachometer Reading High

I would check out the alternator and voltage regulator first to see if it is ok. Since the tach gets its info from the alternator.

I have a 4108 and the original tach went bad on mine. I replaced it with a generic tach, but had trouble calibrating it. I put on a high output alternator and the tach was never right after that. I switched to a Tiny Tach that does not run off alternator.
Bill S is offline   Reply With Quote
Old 23-05-2011, 16:13   #3
Registered User

Join Date: Dec 2008
Location: ontario canada
Boat: grampian 26
Posts: 1,743
Re: Perkins 4108 Tachometer Reading High

You might try checking the voltage/current at the tach. to see if it agrees with the manufacturers spec.
perchance is offline   Reply With Quote


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not 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 Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Perkins 4108 Overheating irwin_37 Engines and Propulsion Systems 27 11-09-2011 17:09
Tachometer not Reading While Charging Wainui Electrical: Batteries, Generators & Solar 5 14-09-2009 16:54
Adjusting Volvo Tachometer Reading Sunspot Baby Electrical: Batteries, Generators & Solar 4 01-08-2009 09:31
Perkins 4108 Passport 42 Engines and Propulsion Systems 6 09-11-2008 22:03
High moisture reading . CARL Monohull Sailboats 13 08-02-2006 05:49

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities

Copyright 2002-2015 Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 19:03.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.