Yanmar 1GM Overtemp Alarm / Thermostat

[n5ama]

Originally Posted by skipperpete

There still remains the possibility that the cause of the engine overheats is that the head gasket is blown across to the waterway.

I agree, that is a possibility but I’ll try the simple remedies first in hopes that fixes the problem without pulling the head.

[n5ama]

Originally Posted by skipperpete

There still remains the possibility that the cause of the engine overheats is that the head gasket is blown across to the waterway.

I’ll try the simple stuff first.
Also if that were the case, I would expect there to be water discharged with the exhaust.

[Phil_Fr17]

The best thing is to prepare for the worst, so have a supplier not too far away to avoid having the engine open too long, causing nervous breakdown (I don't remember how it goes up, in which direction, in which order...).

Concerning skipperpete's remark, justified, we do not know the number of hours of engine operation, therefore its possible 'clogging rate'. It is possible that the cylinder head gasket is tired, badly positioned following a previous reassembly. It is also possible that it is the scaling caused by a long use of the engine to leave the port...
The only solution to find out is to dismantle the cylinder head and inspect.

[n5ama]

The head has never been removed from the engine. I’m not saying I don’t have a head gasket issue but I’ve always focused on the more common problems before advancing to the more problematic and difficult to evaluate. That’s why I checked the exhaust elbow first, then replaced the thermostat (which was the original one installed in the engine) and then addressed the temp sender.

The boat spent it’s first 30 years in fresh water Lake Superior before I towed it down here to the Gulf of Mexico. After a anode metal type change, I put it in the water where it been working fine for 2 years prior to the recent overheating problem.

I have a high confidence level that the problem is accumulated scale in the engine but after giving the acid treatment a chance to work, I’ll dig a little deeper. We are fortunate to have a Yanmar supplier with a 1 week turn-a-round time on any parts necessary for repair.

Have a great weekend,
Tom

[bil56]

if you remove the cylinder head, apart from descaling, you have to:
change the valve stem seals (not expensive),
valve lapping (valve lapping kit, a few $),
check the cylinder head (tightness and planimetry), possibly a slight surfacing in a millling workshop.

./.

[skipperpete]

Sorry for the photo, the data link failed just before I hit send and the “save draft” doesn’t work on my iPad [ATTACH]265223

[n5ama]

I finally got back to my boat (the boat with the temp alarm sounding off after a few minutes). I found that 1/2” clear plastic hose was a good fit for the fittings on my Yanmar. I almost didn’t need clamps. A small cheap pump was connected to the “T” fitting near the water pump and another was fitted to the Thermostat fitting to return the acid pumped through the block. I pumped fresh water to insure that I didn’t have a leak and spray acid around the area. I initially had to punch through a buildup of scale that I pumped out with the fresh water.

I then pumped 1/2 gallon of the full strength acid and got all manner of evil crud out of the block with bubbling and varied in color from dark brown to almost black. After 1/2 hour the returns were less bad looking and fewer bubbles. I then changed the acid to the remaining 1/2 gallon of acid. This time the discharge was generally brown but fairly clear. I pumped this about 20 minutes until the pump failed. I then drained what I could and using a spare bilge pump, I circulated fresh water for another 15 minutes.

I put the engine back together and ran it for a hour without the alarm going off and noted a much stronger flow of water in the exhaust. I also measures the head temp at a maximum of 132 degrees running at 2000rpm. The temp at idle runs below 100.

The temp sender never went off so I feel the problem is solved. I did change the thermostat and the temp sending unit. I needed the thermostat but the removed thermostat will just go to the spares box.

Thanks everyone for the help.

Tom

[Wotname]

Thanks for the feedback Tom, sounds like a good outcome.

Have you replaced the zinc anode?

[n5ama]

I haven’t yet but I have a spare for the Yanmar and will di next visit. I’ll have to wait until I pull the boat out of the water to replace the anode on the prop.

Thanks for the reminder. In all the excitement I forgot about the anode. I’ll do it at the same time I deal with the bilge pump.

Tom

[n5ama]

BTW, I determined the control switch on the bilge pump had failed. I ordered a new Rule 1100 gph pump with the built in switch but determined the old pump had a discharge fitting that was about 1 1/2” diameter and the Rule pump was about half that diameter.

Back to the drawing board. I may replace the switch until I determine exactly what size of bilge pump I need to replace the existing pump. In a perfect world, I would find a automatic pump with the proper discharge diameter.

Tom

[n5ama]

It seems my Rule 1100 GPH automatic bilge pump is not returnable through Amazon even though the pump is unopened and in its original packaging.

I guess the next best thing is to use it in the bilge as a backup pump. The problem that still remains is the pump has a much smaller discharge port. I really don’t want to run another bilge pump line to the stern and cut a hole in the hull for the discharge.

What is the “normal” and conventional way to rig this pump? Is there a source for a reliable “T” or “Y” fitting to plumb the extra bilge into the existing discharge line?

Any help or advise greatly appreciated and thanks in advance.

Tom

[Phil_Fr17]

Some products cannot be returned to Amazon, but it is possible to get a refund by contacting them (email or chat) and explaining the problem or the lack of information on the product sheet that led to this incorrect order.


I did this for several products, I kept the product, and AZ refunded me immediately.


For your discharge that is too small (if I understand correctly), you will have to tinker and adapt the diameter between the pump outlet and your outlet hose.


If you put a 'Y' or a 'T', you absolutely need a non-return valve on each of the two pipes or outlets coming from the pumps, otherwise, the principle of communicating vessels applies... :-(

[Wotname]

Originally Posted by n5ama

..........
What is the “normal” and conventional way to rig this pump? Is there a source for a reliable “T” or “Y” fitting to plumb the extra bilge into the existing discharge line?

Any help or advise greatly appreciated and thanks in advance.

Tom

The normal (and proper) way to to plumb two bilge pumps is for each to have its own discharge hose.

If the new pump has a smaller discharge port, there is nothing wrong with fitting an inline adapter to upsize to the larger discharge hose.

[Rumrace]

Most thermostats are bi metal. Bi metal and moving water hmmm. It’s my experience seasonal stuff cars boats need annual thermostats. The BMW plastic impeller seems to break only in the spring so Bimmer enthusiasts use a bronze impeller. Impellers, fuel pump membranes, thermostats filters all easy laymen annual replace.

[n5ama]

Originally Posted by Rumrace

Most thermostats are bi metal. Bi metal and moving water hmmm. It’s my experience seasonal stuff cars boats need annual thermostats. The BMW plastic impeller seems to break only in the spring so Bimmer enthusiasts use a bronze impeller. Impellers, fuel pump membranes, thermostats filters all easy laymen annual replace.

I’m so confused

?????