J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Adding a temp gauge - 2GMF with B-panel

My Yanmar 2GMF overheated this weekend for the first time. Was running for about 45 min at 2000 rpm. Decreased to about 1000 rpm for about ~2 min, then went to idle forward to pull into the slip.

Just a moment before I really needed a lot of power to keep the boat off of the dock in some heavy Charleston current, the temp alarm came on and when I went hard astern, the engine noticably bogged down. A well placed fender prevented a lot of damage to a neighboring boat.

I've not ruled out the I simply just decreased the RPMs too quickly which didnt give the engine time to cool, but from reading various posts on this list, it looks like there are several common problems that cause overheating.

In the mean time, I would like to add an engine temperature gauge so that I can keep track of what is going on. I'd like to add the gauge without affecting the current warning light and alarm.

Is this possible or do I have to get rid of the stock temp sender to install a sender for the gauge?

If anyone has added a gauge - what parts did you use and where did you locate the actual gauge?

Hoping someone can save me some research time.

Thanks,

Dan M., J-30, "White Dolphin"

I added one in-line to the line that runs from the engine to the hotwater tank. This is not perfect but it gives me a good indication of what the water temp is.

I ordered a VDO Temp guage and sending unit from Torresen Marine http://www.torresen.com/ . Then I found a T fitting at home depot that I used to "tap" into the hotwater line.

David
#397

Thanks David. I was about to go down the same path when I found this:
http://www.egauges.com/vdo_send.asp?Sender=250F_120C

See part number: 323-026

Its a VDO sender with two contacts, one for the VDO gauge, and the other for warning light operation (triggering at 209F). It says the thread size is 5/8-18 NF-3 (in a previous post, USA-90 mentioned that the thread size for our 2GMs was 5/8").

Has anyone seen this or know why it might not work? I dont know if 209F is is the proper alarm trigger temp or not.

I was about to go down the "T-connector in line to water heater" route when I found this, so I may be tempted to get the VDO gauge and two different senders to give this a try.

-dan

Thought I would add an update to this. The dual-contact sender didnt work out, so I ended up going the "T-fitting in hose to water heater" route.

Everything seems to work, but the gauge never seems to exceed ~102F no mater how long I run the engine for.

As it turns out, I didnt have a 2GMF, but rather a 2GM with a fresh water conversion.

From what I can tell, the water going to the water heater is always a mix of what was allowed through the engine by the thermostat and the water that was routed around the engine, which may explain the low temperature.

I'm still not totally sure I can trust the measurements I'm getting, but I've not overheated yet, so we shall see.

-dan

Dan - the only place to sense the "real" temperature is on the engine side of the thermostat. Unfortunately there is no external plumbing on the 2GM that offers visibility on the engine side of the thermostat. There is a by-path connection on the outside of the thermostat that prevents the water pump from discharging to "blocked" system when the thermostat is closed. Any hot water exiting the engine by the thermostat is mixed with this cold water. Hence the cold water sensing symptoms you saw. The cooling water temperature switch on the 2GM screws into the thermostat housing on the front of the engine. This would be the only place to screw in a sensor and drive a gauge to get an accurate water temperature reading. If you look at this link, you'll see the Yanmar service manual Chapter 8 (Cooling System): http://www.j30.us/files/yanmar-cooling-system-chapter8.pdf
Page 5 has a schematic of the closed loop system (Freshwater Cooling). The picture on the 2nd to last page of this Yanmar operation manual has the raw water cooled system: http://j30.us/files/Rhapsody/yanmar-manual.pdf

You can see how the cooling water piping and the switch screwed into the thermostat housing on page 32 of this presentation: http://j30.us/files/Rhapsody_Yanmar_Rebuild_Winter_2006-2007.pdf

Just curious - what didn't work on the dual-contact sender? You could test it in a glass of water. Hook up an ohm-meter across the gauge terminals and pour boiling water over the sensing end. The resistance should increase. The spec is 10-180 ohms. If you want to get real scientific you could build a little fixture with a thermometer and plot the resistance vs temperature. The switch on the over-temp side should close at 209 degrees F +/- 5 dgrees.

Bill

Thanks for the links - this certainly confirms waht I had concluded.


I got the dual contact sender in and went to install it and the threads were entirely different. Around this time I also got a new impeller in that was wrong too. Between these problems I finally figured out that I had a freshwater conversion of the 2GM and not a 2GMF.

It's possible that a dual contact sender is available with the right threads (3/8" 19) but I have not been able to find one. I finally took the path of least resistance and went the spliced-hose route, but this now seems all but worthless.

I found a thread where people talked of re-tapping the port so that a 3/8-18 sender would fit - but I'm not willing to go that far!

-dan

Thanks for the info Dan. I found a good explanation on what the thermostat setting and temp gauge/switch setpoint should be for raw water and fresh water cooled engines on a Yanmar help website. http://yanmarhelp.com/s_faq.htm

I pasted the applicable Q&A below.

Q: My engine thermostat is set to start opening at 105 and be fully open at 112. I think this is much to low but it is the original stat from Yanmar. The oil never gets hot enough to burn off the byproducts of combustion. The temperature gage never gets over 100, even after motoring all day.

A: A salt water cooled engine operates at about 55degC / 130degF., you can keep your hand on the cylinder block while the engine is running. If the temp goes over this the salt will precipitate out of the water and restrict the water galleries at an unacceptably fast rate. Also, because of this, the alarm operates at 62degC / 144degF. The raw water cooled engine thermostat starts opening between 104 -112deg F and is fully open at 125deg F. Because the reading is quite low gauges are often inaccurate, and may be a reason yours only reads 100degF most of the time. Most gauges are the same except test gauges which are not practical and very expensive. Even with freshwater cooled engines, that operate at higher temperatures, the oil retains the byproducts of combustion and always looks black. The best way to help get rid of contaminants is to rev up the engine for a half minute (over 3000rpm), out of gear, before moving the lever back to idle and shutting down. Do this at the last stop of the day if stopping and starting a lot. Also run the engine at 3000rpm or over for 10 minutes or more, for every 5 hours of slower running. 2000- 2500 is very slow. The engine will prefer 2800rpm or thereabouts.

Response from VDO:

"Mr. McGraw,

Unfortunately, we do not make a temperature sender with a warning contact that has 3/8" threads."

Oh well...

You can try: http://www.nhspeedometer.com/senders.htm
250F 5/8-18 NF-3 203 +/- 5F 803/1/1 323 487
fits Yanmar 2QM15
It is odd that the thread on 2GM is 3/8-19?

The 3/8-19 does sound pretty funny, but that translates into roughly M9 X 1.25. VDO should have an equivalency chart on their website....well maybe. If that's a tapered pipe thread it could be M10 X 1.25, too.