E32-3 with Univ M25 - Cooling system

During my sea-trial on an E32-3, the surveyor said he noticed "steaming" of the exhaust, without significant signs of past or present overheating. The Ericson owner's manual says to fill the water heater with water and to bleed the system before running the engine. This boat is equipped with the standard water heater, but the water system was empty when we did the trial, as the boat had just come out of winterization.

Are current owners really keeping the water heater filled at all times for engine cooling? Sounds like that water would get pretty nasty without being changed frequently.

Does motoring without fluid in the water heater adversely affect engine cooling?

Another member posted of his satisfaction with the larger, 3" heat exchanger on the M25 (the boat I'm considering has the 2" exchanger). Is more = better when it comes to heat exhangers on the M25, or are there other factors to consider (other than $$ of course--I know the answer to that one)?

Thanks.

Cooling System

I inquired of the forum a few years back about the same situation,

I bypassed the hot water tank as I never use it, and have no cooling problems.

You might have an airlock in the system if the water tank and relevant lines are not properly bled....should be looked into carefully.

Good Luck

Mort Fligelman said:

I inquired of the forum a few years back about the same situation,

I bypassed the hot water tank as I never use it, and have no cooling problems.

You might have an airlock in the system if the water tank and relevant lines are not properly bled....should be looked into carefully.

Good Luck

Click to expand...

My experience with an M25XP and a water heater is that an airlock in the system will cause a severe overheat condition in short order. When changing the coolant (another regular maintenance item), it is important to pump the coolant through the entire system so that it is purged of any air. When the time comes for Kenneth to do that I can provide step by step instructions for how to do it in a way that makes sure there is no air in the system.

Steaming Exhaust isn't about engine block cooling

This reply and mini article is based on fresh water cooled engines:

Generally steaming exhaust on water cooled exhaust systems is not about engine overheating. There are two systems that are interconnected out of convenience, engine cooling and exhaust cooling. (They do share a 1 of the two pumps).

I have seen several engines rebuilt because of steam coming out of the exhaust. In all of these cases, the problem was not solved by the rebuilding of the engine, and in one was not solved by the replacement of the engine entirely with a new one.

Steam is generated in the exhaust by a lack of sufficient water in the exhaust cooling portion of the raw water circuit. The other side of the cooling circuit, the engine cooling side, does not generally have an effect on steam in the exhaust in most situations.

Trouble shooting and thinking it through steps:
#1> If the steam were coming from the engine cooling side on a fresh water cooled engine then the radiator cap would pop and fill the interior of the boat with smelly Propylene Glycol steam and a temperature gauge pegged.
#2> If the steam were coming from the mixing of the cool raw water with the engine cooling water, then the engine cooling water would have to be really hot to heat up the raw water to above 212 degrees (100 Degrees for those of you on the French system). That much heat and steam on the fresh water side would pop the radiator cap, and we would have #1.
#3> If the steam were coming from the cool raw water itself, you would not be able to float in the water without being cooked like a hotdog in foil, so we can discount floating on a sea of steam (Just put this in here to see if you were reading it!).
#4> Insufficient cooling water going through the heat exchanger, or a significantly undersized heat exchanger would again cause #1
#5> So the only place left for the steam to be generated has to be outside the engine block:

#6 > There is no heat added to the raw water once it leaves the heat exchange at any other place except where the exhaust gases mix in at the mixing elbow (also called the raw water injection point by some mechanics).
#7 > Insufficient water through this point or having the cooling water vaporized could create steam where it mixes with the 500+ degree exhaust gases. (500 degrees.... Hummm That could produce steam easily if it were not cooled enough or fast enough).

Lets take a look at this crude drawing that is provided by my doppleganger and see if it makes sense. (He isn't very good at photo shop is he?)


So how to fix it?

Take the mixing elbow off, and clean it out, or in most cases replace it.

Also check to make sure that your impeller on the raw water cooling pump is new and that you are not restricting water through the raw water system.:
#1 >Thru Hull (Likely to cause high engine temp)
#2> Strainer (Likely to cause High Engine temp)
#3> Hoses (These can have aneurysms where the internal layer separates and causes a full or partial hose block in some conditions, rare, but not unheard of).(Likely to cause high engine temp)
#4> Heat Exchanger (A frequent issue is broken off impeller bits from previous impeller failure stuck against the raw water tubes. Most times you can get them out with a set of magic fingers). (Likely to cause high engine temp)
#5> Exhaust cooling injection point, or mixing elbow. (Does not cause high engine temp generally).

That should help, and start some conversation that might help.

Guy

Oh and if you want to see how a heat exchanger works

This is a better drawing than my doppleganger can do:

https://en.wikipedia.org/wiki/Shell_and_tube_heat_exchanger

Guy Stevens said:

This reply and mini article is based on fresh water cooled engines:

<snip>

Click to expand...

Thank you for this excellent information, Guy! A follow up, if you don't mind....

I have a Yanmar 1GM, which is raw water cooled. The engine runs very cool--it will barely get to around 100 degrees most of the time. Yet, I often get what appears to be steam when running it at cruising rpm. I'm pretty sure it can't be smoke based on how quickly it dissipates. It's not a large quantity but is usually present, and seems to vary with the atmospheric conditions (e.g., more in higher humidity). I've figured it was related to condensation in the exhaust system but it continues even after running the engine for a long time. The exhaust water is hot but not too hot or scalding; I can keep my hand in it without harm. The exhaust elbow is about a year old.

If your thoughts on this will take us too far afield of the original poster's question then maybe we can start a new thread so I don't hijack his.

Thanks.</snip>

Ken,

In reference to the 2" vs 3" heat exchanger. I have the Universal 5424, 3 cyl, 24 hp predecessor to the M25 in my 1981 E36RH. My boat lived in Santa Barbara before I brought it to the Chesapeake. It still had the original 2" HE. All diesel functions and cooling worked fine for my first few short sails and short motoring trips. I then had a longer ~ hour motor home in August with the Bay temperature 80+ degrees. I was running hot at 185 with a 165 degree thermostat at the end. I checked out my 2" heat exchanger and it wasn't blocked, but decided to upgrade to the 3" HE since I am always going to have warm seawater intake in the summer. My engine always runs at 165 now. The SeaCamp 3" Nickel Copper HE I got online was less than $200.


Since you are in the NW with cold seawater, you may well get by with the 2" HE if there is no blockage and all else in the cooling system is working as designed. I would check inside for blockage and make sure the rest of the system is good. If it looks like you should spend more than a little money on a cleaning or radiator shop work on the 2" HE, I would strongly consider putting that money into a new 3" HE instead.

Mark

Agree completely about moving up in size if replacing.

Also, not fixing what's not broke. (30 hours nonstop motoring in Hawaiian waters, no problem. Except the Sherwood raw water pump blew its bearings. But, just another anecdote).

Overheating is one of those worry points, and I myself spend too much time looking at the temperature gauge. Which may or may not be accurate. And which never got above 165 on the 32-3, causing some correspondents to warn I was "running too cold."

The specs give quite a range of "normal," with question marks.

"Eng. Operating Temp. Degrees F. 165� to 195�"

I would like to know more about all this.

http://www.marinedieseldirect.com/universal/200157/universal-owners-manual-m25-specifications.html

Oh, and something else:

A newly acquired boat with maintenance somewhat deferred is very likely to have the heat exchanger full of old zinc shards, impeller pieces and assorted nameless glop. The end caps come off with one bolt. The junk can be picked out easily by hand or tweezers. The gaskets that seal the HX end caps are $3 and are supposed to be replaced periodically, which is maybe why so many 30-year-old caps are corroded and seepy. All in all, this clean out and sanity check is one of the simplest jobs on the boat, and contributes to peace of mind. Also good training in reaching things that appear impossible to reach, which is one of the skills of owning a small boat. Esp. an E38, with the engine encased in fine furniture.

Christian Williams said:

Overheating is one of those worry points, and I myself spend too much time looking at the temperature gauge. Which may or may not be accurate. And which never got above 165 on the 32-3, causing some correspondents to warn I was "running too cold."

The specs give quite a range of "normal," with question marks.

I would like to know more about all this.

Click to expand...

The diesel experts on the forum can chime in to confirm or deny, but I think the reason for the temperature range has more to do with the heat exchanger than the engine. The engine is actually happier running at the higher temp but the problem is you increase the likelihood of salts precipitating out on the raw water circuit and clogging up the exchanger--especially bad with the marginal 2" exchanger, I would think. When I replaced the thermostat on my M25XP years ago, the Universal dealer (Captain's Locker in Seal Beach) provided a 165-deg. one, which was the factory supplied part.

One point that should not get lost in all this is that an engine with a properly functioning cooling system should run at the thermostat temperature once warmed up. So if that thermostat is 165 degrees the engine should not run over that. If the temps start to climb, e.g., when running it harder, it probably indicates something borderline about the cooling system, be it a marginal heat exchanger, impeller pieces or other debris clogging up the works, etc. etc.

My M 25 runs happily @ 185 degrees. It may be a simple difference in the thermostat.

BTW, you haven't said if you measured the heat exchanger yet. If you do need to change it, it is best to do it at the same time as the alternator bracket since you have to drain the coolant for each of those jobs. Both easily done in 1 day, afaik.

Christian Williams said:

Agree completely about moving up in size if replacing.

...
A newly acquired boat with maintenance somewhat deferred is very likely to have the heat exchanger full of old zinc shards, impeller pieces and assorted nameless glop. The end caps come off with one bolt. The junk can be picked out easily by hand or tweezers. The gaskets that seal the HX end caps are $3 and are supposed to be replaced periodically, which is maybe why so many 30-year-old caps are corroded and seepy. All in all, this clean out and sanity check is one of the simplest jobs on the boat, and contributes to peace of mind. Also good training in reaching things that appear impossible to reach, which is one of the skills of owning a small boat. Esp. an E38, with the engine encased in fine furniture.

Click to expand...

Also - one of the uses for coat hanger wire on board is that it is the perfect diameter and stiffness to push through the heat exchanger tubes (removing assorted nameless glop).

and then the light came on

Click. And then the light came on. But it was only a dim and flickering one at that......

Many thanks for all the replies, especially to Guy for the (actually pretty good) photoshop illustration and the humorous-but-on-point analysis of cooling system problems. Until your explanation, I couldn't understand how the exhaust could be steaming while the engine was operating at a normal temperature. I could grasp that the raw-water "run" is separate from the engine cooling 'loop", but I didn't know that the raw-water run is later re-combined with hot exhaust gases in the mixing elbow. I imagine that this is both (1) to cool the exhaust gases which travel under the cockpit through rubber hoses, and (2) so that the raw water and exhaust gasses can be expelled through a single through-hull opening.

Just to make sure I have this right (see image, below):

(a) the collection of u-shaped pipes that bolts on to the exhaust manifold is the "exhaust riser" (some web entries claim that owner's have rebuilt these with galvanized plumbing connections from Home Depot). And,

(b) the white-ish looking elbow on the right is the "mixing elbow" or "raw water injection point"

I would have guessed (knowing what I know now) that steaming exhaust would be caused by a lack of sufficient quantity of raw water into this point (but as was mentioned, lack of sufficient raw water quantity should also cause engine overheating, which in my case, it's not). I read another related post where an owner claimed he stopped exhaust steaming by replacing the mixing elbow, just as Guy is suggesting.

A couple of additional points:

The attached photo is from http://realitycheck.me/universal-m25-diesel.htm This is the photo-blog of a Catalina 36 owner with a Univ M25. I was astounded by the detailed content on this site related to M25 maintenance and repairs. I'd say it's worthy of comparison to Christian William's Thelonius blog in terms of taking the mystery out of those "how in the hell am I supposed to do that" questions.

While we're discussing the "tail end" of the the engine system, anyone care to explain how a "water-lift muffler" works. Ie, how does the water get into the can to begin with. How does it get or stay filled (wouldn't the exhaust gases eventually cause it to evaporate? And, back to the exhaust "steaming" issue, wouldn't the water in the lift-muffler re-liquefy most of the steam in the exhaust? (Which, in my case, it is not.)

Finally, like Christian mentioned in his comment, I am likely to be a chronic temp-gauge watcher. It's not easy to view the gauge down there in the starting compartment at your feet in the cockpit. Is it difficult to mount a repeater gauge at the binnacle, or to just move the existing temperature gauge there?

and, for way more than you ever wanted to know about exhaust risers and associated problems:

http://realitycheck.me/gallery.htm?http://www.yachtsurvey.com/exhaust_risers.htm&

Kenneth K said:

and, for way more than you ever wanted to know about exhaust risers and associated problems:

http://realitycheck.me/gallery.htm?http://www.yachtsurvey.com/exhaust_risers.htm&

Click to expand...

There may be some good information about engines in his writings, but a number of years ago he was critical of sailboats for having keels, and after some negative comments on sailing forums he removed the article. I would guess that his area of expertise is mostly in power boats.


OTOH, his critiques of shoddy glass layups on power boats (and cheap sailboat layups) were spot on.


Loren

Ken,

That Catalina 36 "Reality Check" website is an excellent resource for all things M25 diesel related (plus other good stuff). I used it to get familiar with all the maintenance (oil, fuel, seawater, freshwater) items I planned to do my first winter.

If your M25 doesn't have the oil drain tube/hose on the bottom of the oil pan, I highly recommend you add it at your first oil drain/change so you will only have one episode of sucking the oil out of the dipstick tube and then draining the rest of it out the bottom drain into a throw-away aluminum basting pan of the proper size. There is a thread on this site which references the P/N for my 5424 and the M25 variants.

Mark

markvone said:

Ken,

That Catalina 36 "Reality Check" website is an excellent resource for all things M25 diesel related (plus other good stuff). I used it to get familiar with all the maintenance (oil, fuel, seawater, freshwater) items I planned to do my first winter.

If your M25 doesn't have the oil drain tube/hose on the bottom of the oil pan, I highly recommend you add it at your first oil drain/change so you will only have one episode of sucking the oil out of the dipstick tube and then draining the rest of it out the bottom drain into a throw-away aluminum basting pan of the proper size. There is a thread on this site which references the P/N for my 5424 and the M25 variants.

Mark

Click to expand...

Picture of our drain fitting in reply 12. It's a great solution.
http://www.ericsonyachts.org/infoexchange/showthread.php?6036-Oil-Change-Process
If your Universal diesel does not have this option, you will want to add it.
I have a blog entry on sourcing the best washers for the fitting, as well.

Loren

Why would there need to be a high loop in the raw water hose between the heat exchanger and exhaust manifold?
My m25 has one.

I have found, as others on this site have noted that the brackets that bolt the heat exchanger to my M25 XPB are broken. I have removed the heat exchanger and it looks like I can clean it, replace the gaskets and use it.


The problem is I need new brackets to mount it back onto the engine. Anyone have experience with this?

Thanks!

Peter
1988 32-200

Check here

http://www.marinedieseldirect.com/c...comment1=Part number 299835 is for the M-25XP.

Part II: E32-3 with Univ M25 - Cooling system

This is a continuation of a thread I started in July after my boat survey. The original problem was:
Just this week I got around to removing the exhaust manifold and riser/elbow from my M25, as part of my alternator bracket replacement project.

The findings are pretty interesting:

I suppose that's the benefit of DIY projects--you get to learn a lot along the way. Though removing and cleaning the entire riser/elbow is a real P.I.T.A. (with the engine in the boat, anyway) in this case, simply removing one hose and replacing one fitting would have allowed me to fix most of the blockage. That's something to think about for the ongoing repetitive maintenance routine.

BTW, Guy Stevens...... you nailed it!