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  Topic Review (Newest First)
06-18-2013 10:40 AM
Re: Yanmar 2QM15 Overheating Problem

Thanks everyone for the input. I won't slick 50 it. I probably should have titled this "Underheating Problem". More and more I am thinking that this is not a problem. Engine is currently running at about 85-90F and maybe that is what I should suspect at low load, low rpms in 52F water. I'll move on to my next major problem- trying to find a new/used lower gudgeon for my Columbia 29 MarkII. or some pictures/specs, material. Mine is gone, probably a victim of galvanized corrosion. Last owners spent most of their time destroying the original interior.
06-13-2013 07:30 PM
Re: Yanmar 2QM15 Overheating Problem

The reason for keeping the water temp low in a raw-water cooled engine is to minimize scaling in the engine cooling passages. The Universal 5411 in my previous boat ran at about 140F. Fresh-water cooled engines run the cooling water (anti-freeze) at 180F.
06-12-2013 08:36 AM
Re: Yanmar 2QM15 Overheating Problem

Contact Torresen Marine to find out about the thermostat. I wouldn't use Slick 50. Don't know if it would hurt anything but...why?
06-12-2013 02:15 AM
Re: Yanmar 2QM15 Overheating Problem

Thanks to both of you for your helpful replies. I stove tested my thermostat this evening and it seemed like it was opening at about 100F. I'm a car nut and it just seemed to me that 85F was low for a healthy operating temp but maybe it's good. Does Yanmar offer higher temp thermostats? Should I look for one with a higher temp rating? BTW, is Slick 50 a good idea in a diesel?
06-11-2013 11:04 PM
Re: Yanmar 2QM15 Overheating Problem

The 2QM15 thermostat begins to open at 42C (108F) and is full open at 52C (126F). That's why your thermometer doesn't register. The hole is likely an equalization hole to limit pressure/temp differences when the thermostat is closed during warmup. Sounds like your engine is being adequately cooled. Your goal of clean water passages and zinc protection and good cooling seem to have been met. Bravo!
06-11-2013 03:29 PM
Re: Yanmar 2QM15 Overheating Problem

I believe the normal operating temperature is about 130. That was about as hot as mine ever got and that was in 80 degree water. Rule of thumb I was taught was that you should be able to put your hands on the block for a few seconds without getting burned. It should be very warm but not "burning hot".
06-11-2013 11:25 AM
Re: Yanmar 2QM15 Overheating Problem

This has been a great thread. I recently bought a 1966
Columbia 29 Mark2 with a converted 2QM15 with purported flow problems. The boat had been neglected for three years and the forward zinc was down 50% and its debris had occluded the bypass tube. I scraped all of that out. The aft zinc was totally gone. Problem? Engine won't warm up. I bought and installed a mechanical temp gauge that begins at 130F and it won't come off the needle. I'm going to replace with one that starts at a 100F. The thermostat looks OK but I haven't tested it on the stove yet. Why is there a 5/32" hole in the top end? Any ideas why it might not be warming up? Current sea temperatures are about 53F. What temp should the thermostat open at and what is the usual operating temp? The manual says not enough to burn your fingers.
Thanks for any help. Hope I am not cutting in on someone's thread.
09-02-2011 08:07 AM
JimsCAL Agree about not using RTV. Permatex makes several products for coating gaskets to improve sealing. Check your local auto parts store.
09-02-2011 06:24 AM
fryewe I wouldn't use RTV. The gaskets will do the job well unless you have eroded sealing surfaces. Looks like you have all the gaskets listed. Don't you need two zincs (fore and aft)? Zinc packing is copper washer, and usually reusable, but they're inexpensive so I would replace both. Soot in the manifold and exhaust elbow are not a problem, unless it is a very thick coating. It will build back up quickly. You need to run up the engine each time you run it, especially before shutdown for a minute or two, to blow any soot out.

If you were able to dig out and flush out the manifold well, and water is flowing freely through it while it is off the engine, you probably have solved your problem.
09-02-2011 01:00 AM
Summer Magic
Originally Posted by fryewe View Post
More than likely the water passages in your exhaust manifold are plugged. If the manifold hasn't been pulled and cleaned in a few years, it is most certainly plugged. You will have to pull it to unplug it.

When the engine is first started, and the engine is cold, much water is by-passed by the cooling passages of the engine and the exhaust manifold through the bypass line as noted by CrazyRu above. The thermostat should be closed during this time. This allows the engine to warm up faster.

After the engine is warmed up, the thermostat opens to allow cooling water to enter the cooling passages in the exhaust manifold, cooling the manifold, exhaust gases, and the engine. If the exhaust manifold is plugged, cooling flow is EXACTLY the same as if the thermostat didn't open.

You will need a thermostat housing gasket, a gasket for the exhaust manifold to engine connection, a spacer that goes between the manifold and the engine where the two aft-most studs for the manifold are, a gasket for the blanking plate on the forward end of the manifold, and a gasket for the flange (plate) on the aft end of the manifold where the mixing elbow attaches. If you have the 45 degree mixing elbow, and it is good shape, but it hasn't been off for a while, do not try to disconnect the elbow from the flange on the aft end of the manifold. That flange wasn't available as a spare last time I checked, and if you bugger it up, you may have to repair it or have a substitute made. Pull the manifold and mixing elbow off the engine, then disconnect the mixing elbow and its flange at the manifold connection, pull the blanking plate off the forward end of the manifold, and start digging out the corrosion with tools that won't damage your manifold. Replacements aren't available. Inspect it carefully before you start. They are prone to crack with age and the thermal stresses of their life, especially if they have been overheated and then cooled rapidly while still hot. Cracks can be welded or solder repaired.

The hardest part of this job the first time I did it was getting the mixing elbow and exhaust hose connection apart. I tried to take the hose off the elbow as the first step. Next time I did it, I pulled the manifold and exhaust elbow off the engine so I could pull it forward off the hose. MUCH easier.

Hope this helps.
Here is the parts list I intend to order... I have a U shaped elbow not the 45 degree version. Do I need to clean the mixing elbow too or just the manifold?
Should I use a product like Carbon off to clean out the soot in the manifold?

124770-13171 aft exhaust flange $10.07
124770-13181 forward flange $10.06
124701-11911 Manifold Gasket $10.29
124770-13131 Mini 2bolt Gasket $2.05
27210-200300 Zinc $4.05
23414-250000 Zinc thread packing $0.96
104211-49160 Thermostat gasket $1.53
27210-200300 Aft Cylinder Head zinc $4.05
23414-250000 Aft Cylinder Head zinc thread packing $0.96
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