Cruisers Forum

Join CruisersForum Today

  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
Thread Tools Search this Thread Rate Thread Display Modes
Old 04-10-2008, 20:13   #1
Registered User

Join Date: Apr 2008
Location: Atlantic City, NJ, USA
Boat: 1984 Hunter 31
Posts: 3
Overheating Yanmar?

I have a 1984 Hunter 31 with the original Yanmar 2GMF fresh-water cooled 13 HP motor. When I motor at 2500 rpm or lower the temperature is fine. When I approach 3000, the audible alarm at the cockpip panel begins to emit a faint alarm. As I continue to motor (in gear, under way) at 3000, the alarm gradually gets louder. When I back down to 2500 rpm or lower, the audiable alarm gadually fades away. Is fading in and out the normal function of this alarm? I assume it is, so I've taken some steps to stop the overheating. I've checked the raw water strainer and pump and they are ok. I've replaced the thermostat and cleaned the raw water side of the heat exchanger. Still no improvement. I'm next going to perform a flush on the fresh water system. If this does not do it then I'm fresh out of ideas. Has anyone had this experience that can steer me in the right direction? Any suggestions would be greatly appreciated. I'm about to make a 25 nm trip to her winter home with most of the trip being under power.
Thanks, Ted in NJ

Zephyrus is offline   Reply With Quote
Old 05-10-2008, 01:03   #2
Senior Cruiser

Cruisers Forum Supporter

Join Date: Dec 2006
Location: Seattle
Boat: Cal 40
Posts: 2,558
Images: 7
The alarm is connected to both the coolant temperature and oil pressure senders. These are both just switches, so the alarm should either be off or on, no in between.

Have you looked to see which warning light is on while the alarm is sounding?

Does the alarm sound loud and strong when you turn the key to on with the engine off?
Do the charge and oil pressure lights come on with the key on and the engine off?

If you have the tachometer version of the panel, the switch that turns on the instruments light when pushed to one side, tests the coolant indicator light when pushed in the other direction.

Could be a defective oil or temp sender. They should read either as a short or open. Oil is closed (short) no pressure, coolant is open cold.

Could also be a poor connection to or from the alarm, such that you do have an engine problem, but poor alarming.


cal40john is offline   Reply With Quote
Old 05-10-2008, 05:34   #3
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Boat: Bestevaer.
Posts: 11,642
Dear Ted
I am no expert, but it sounds to me more like an electrical (wiring or sender) issue than a true overheating problem.
Try turning off the ignition disconnect the wire from the sender (It will be screwed into the block often near the thermostat about 2cm diameter and copper coloured with one wire coming out of it) and measure with a multimeter on the Ohms scale from the sender terminal to ground. It should read infinite Ohms when the engine is cold and close to 0 ohms when the engine is overheated (about 95 deg c).
The oil warning light will read the opposite 0 ohms when shut down and infinite when the engine is running.
Some multimeter's have a temp measuring thermocouple (or use an infrared thermometer) try this on the sender (ideally measure the temp before you have a problem ) with the engine running it should be about 85 deg C.
Hope this helps John
noelex 77 is offline   Reply With Quote
Old 05-10-2008, 06:14   #4
Registered User

Join Date: Jun 2005
Posts: 1,901
whats the max RPM you can get in gear underway?
never monday is offline   Reply With Quote
Old 05-10-2008, 14:25   #5
Registered User

Join Date: Apr 2008
Location: Atlantic City, NJ, USA
Boat: 1984 Hunter 31
Posts: 3
Overheating Yanmar?

Thanks, guys. It never goes into full-volume alarm and the light never lights. I'm going to check the things that you recommended. I do have an analog thermometer strapped on the closed loop hose that's between the thermostat and the heat exchanger and It's never read more than 160F (71C). A faulty sender would be a heck of a lot better than a cronic overheating problem! I'll keep you posted.
Ted in NJ
Zephyrus is offline   Reply With Quote

overheating, yanmar

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
Overheating Atomic 4 SanJuanCruiser Construction, Maintenance & Refit 21 14-06-2010 13:42
Coil overheating Hankthelank Engines and Propulsion Systems 2 02-08-2008 19:16
Overproped=Overheating jpv Propellers & Drive Systems 6 19-09-2007 12:26
overheating 3QM30 bmjpv Engines and Propulsion Systems 15 16-07-2007 01:04
Yanmar overheating seagypsywoman Construction, Maintenance & Refit 42 20-09-2006 13:41

Advertise Here

Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 14:48.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.