Persistent Overheating Issue

[barfwinkle]

Okay first and foremost this pic is not from Rhapsody.

Second, and aside from the obvious threat to the safety of the vessel and crew, could this be the source of a persistent overheating issue in a Yanmar 1GM? The red hose is the feed line to the water pump.

[Sea Hunt Video]

Bill:

Your photo did not show up on the post - or I guess I should say, at least not on my computer

[Oswego John]

Ditto.

O J

[barfwinkle]

did this work?

[Russell]

There are many, many things wrong in that photo, but nothing that would cause overheating of an engine.

[Sea Hunt Video]

Photo worked

Bill, as you know I am a rookie but when I think of "persistent overheating" I think of things like:

1. a partially clogged intake hose. The photo does not show a raw water filter.

2. a partially damaged impeller.

3. a clog in the Yanmar 1GM engine plumbing for the water to circulate. I had this issue. A diesel mechanic "flushed" the system with a chemical that dissolves all of the built up crud, etc.

As I said, thoughts of a rookie.

[Steve Kuhar]

Bill,

Are you sure that it is an overheat problem? The temperature sensor on the 1GM is notorious for acquiring deposits that cause a false overtemp warning. Our local Yanmar expert told me to put my hand on the cylinder head and count to five. If your hand is still there, you do not have an overheat problem. If you don't have a strong desire to move your hand you are running to cool. I have tried this with my engine and it seems dead on when compared with a direct reading temperature guage.

Steve

[John Martin]

Make sure the engine coolant is topped off. This fixed an overheating on 'Intrepid', CD-28. JM

[Doug Hill]

My 25D, Meander, with a 1GM started overheating this summer, but only at slow rpm (1000 or less) It did not overheat at cruise rpm.

I did the following things in sequence. Checked the impeller and it looked ok. I replaced the thermostat. The old one (perhaps original) was clearly toast. Still overheated. Used Rydlyme flush. Still overheated. Replaced the temp switch and the impeller and I have a happy little 1GM again. It doesn't overheat at any rpm and actually seems to run smoother than it did before. If I were to do this over again I probably would replace the impeller first, then the other items, but overall, a few hours and about $100 was time and money well spent. I also learned some things about the little beast.

This last weekend I ran her hard on Lake Michigan, watching the Melges 20 National championship regatta. A Cape Dory 25D can not keep up with a Melges 20 under any circumstances, but a total of about eight hours of hard motoring and idling, the 1GM did not complain once. So I think I solved the problem.

If I can brag a bit, my son finished eighth overall out of 29 M20's and was the first Corinthian boat. There were pros galore in this regatta including Volvo Ocean racers, America's cup sailors etc. This is the same kid that hated sailing on our first Cape Dory. Yup. Dad is proud.

[Joe Myerson]

Bill,
I had overheating problems with my 1GM for years. Most of them were traceable to impellers that were partially worn-out (the blades looked fine, but they spun freely around the hub), but I've also had to replace the temperature sensors, as well as the water pump. I've also started replacing the thermostat every second season (probably won't do so this year, since I didn't get launched until the last week of July).
This spring, for the first time in 32 years, I removed the raw-water strainer. Doing so, I discovered that generations of nasty sea creatures had deposited their shells and skeletons deep inside the raw-water intake seacock. A nice big screwdriver got rid of those.
I'm not sure if you have those problems sailing in fresh water (or are you now sailing in the Gulf?). But it's worth a try.
Best,
--Joe

[Merilintu]

Bill,

My 22D was on the hard for 12 years+, and the 1GM started on the first try and ran fine for 20 minutes at 3200 rpm. On the 2nd start, and every one after, it overheated. My yard took the following steps, which did NOT fix the problem:

1. Impeller
2. Thermostat
3. Temperature Sensor

I had picked the boat up 3 times and overheated within a mile of the yard every time. Then I started digging in to this and other forums. Was I really overheating? The 5 second test was no problem for me, and my mixing elbow was cold to the touch while the overheating alarm was screaming away. Again, was I really overheating?

I bought the SELOC manual for Yanmar and started learning. I decided to replace every single hose on the the engine. All appeared original from 1984. If that didn't work, I was set to do a rydlime flush. When I started tearing apart the hoses(fused to their fittings), I found tons of tiny rubber bits. They could have been from the old impeller or the inside of the hoses. There are TINY waterways in the thermostat cover that can easily be clogged by virtually anything. I also cleaned out the "T" fitting above the impeller. I also dug around in any opening I could find to make sure it was clear and water wold pass freely. Thankfully, I haven't overheated since.

I was amazed at the small impeller and how miniscule some of the waterways are that keep this thing cool. I did also replace the mixing elbow, but upon inspection afterwards it was fine.

Hope this helps. Keep at it, and you'll find it!