It's not the humidity; it's the heat. Universal M-30

[M. R. Bober]

The only down side of the Chesapeake Fleet's cruise was that RESPITE's Universal M-30 was running hot. This is a new situation.

At 1500 rpm or below, the engine stayed at ~160F. At 1800 rpm or above the temperature would rise to 190F. at which point I would lower the engine speed. I dove and found growth on the strainer covering the seawater intake, which I scraped. This seemed to help, but not enough.

I have flushed the freshwater side of the system, which didn't do much. This evening I removed the thermostat--and while the engine took longer to come to temperature--to find the temperature still heading above 190F.

Soooooooooooooo.......
I am planning to remove the heat exchanger (2") and send it to the radiator shop for inspection/cleaning/testing, but am wondering if I am missing something. Any suggestions would be appreciated.

Mitchell Bober
Sunny Annapolis (where even the bilge is sunny) MD

[Bill Cochrane]

Mitch,

You may have done this, but if not...check the relative temp of the raw water as it enters and leaves the heat exchanger. If there is a fair difference, the heat exchanger is working; if not much, suspect that it needs rodding or cleaning. If there is a sizeable temp difference, the problem is either too much heat being developed or the fresh water system not removing it fast enough...thermostat or some sort of obstruction, scaling, etc in the fresh water side.

Obviously it helps to have done this (comparison) when all was in order, but you can get a reasonable idea if heat is being removed in the exchanger.

Also if either the fresh or raw water pumps are belt driven, check belt tension. Impeller(s).

[M. R. Bober]

I forgot to mention that I had installed a new impeller, but it did not make any difference.

Every best wish,
Mitchell Bober
Sunny Annapolis (where some don't like it hot) MD

[Zeida Cecilia-Mendez]

Make sure the fresh water pump is working properly. If you have an air bubble in the fresh water system, the pump will not work as it should, and engine will overheat. You may need to prime the fresh water pump.

[Rperlot]

My MD7A used to run hot. I couldn't figure it out. I went to change the impeller. When I pulled out the old one, it all looked good. But as I was installing the new one, I was digging around in there for some reason and pulled out a single impeller blade. Apparently, at some time in the history of the boat, a blade broke off an impeller and it was never seen. Other impellers were installed right over the top. There was just enough blockage to over-heat the engine at ~1800rpms. Now I can run at 2300-2400 (for no apparent reason) before it over heats. Of course, I hit maximum speed at about 2000, so there is no point. But I run halfway in the green at that.

Just a thought. you might want to take a close look in there and see if there is something obstructing the impeller from doing a proper job.

Rperlot
CD28 #352

[Steve Laume]

My first rule of trouble shooting is to eliminate the easy ( and cheap) stuff first. I know you said you dove on the strainer and cleaned it off. That is deffinitly in keeping with my thinking. If the yard painted it and you haven't scraped out the tiny little slots they may be clogged with paint enough to reduce the intake. Hey it is summer so another swim sounds much better than messing in the engine comartment. Another problem I could see is growth in the seacock. I don't know when my seacocks were last maintained as the boat was new to me last fall. When I cleaned the engine seacock ther were a couple of mussels growing right inside the barrel. The only way to get at them while the boat was in the water would have been to slid in a long thin blade with the seacock open. It would seem pretty easy to check the strainer. If you have the raw water pump open it might be interesting to open the seacock and see how much flow you get to that point. May all your problems be cheap and easy to fix, Steve.

[Cathy Monaghan]

Hi Mitch,

You mentioned that you "found growth on the strainer covering the seawater intake" and that scraping it off helped a bit. You may need to removed the cover -- yea, I know, it's hard to do with the boat in the water -- and scrape growth out from within the thru-hull fitting and the hose. It could be full of barnacles and slime or even a jellyfish.


Cathy
CD32 Realization, #3
Rahway, NJ
Raritan Bay

[M. R. Bober]

I used a very long pick to "ream" the thru hull, and didn't find much inside. The radiator shop will inspect/clean/acid wash/reassemble/paint the heat exchanger for $150+ any parts. I will be heading in their direction shortly.

Also, Bill the intake water is just under 90F and the exhaust water will melt the skin on your hand.

Mitchell Bober
Sunny Annapolis (where every sailboat marina has an engine shop) MD

[Bill Cochrane]

Also, Bill the intake water is just under 90F and the exhaust water will melt the skin on your hand.

Sounds like heat is being exchanged...

This is a problem (overheating, that is) that my Perkins 4.108 has been plagued with...No matter what, if I run the engine fast enough to approach hull speed, it will overheat. Thermostat, heat exchanger, water pump(s), prop pitch, clean/foul bottom or prop...all have some effect; it overheats at a lower or higher speed, but inevitably it will overheat if I venture very much over six knots (at current prop pitch, about 2200 rpm).

So I'm interested in your saga and eager to learn anything new.

[M. R. Bober]

...I'll confess.

I fabricated a "cap" for the seacock from a section of bicycle tire inner tube (Go Lance!!!) about 6" in length. After removing the seawater to water pump hose from the seacock, the tube was hose clamped to the seacock (seacock closed.) I used wire to close off the open end of the inner tube AFTER inserting a 10" small diameter metal rod (i.e. a length of metal coat hanger, the most useful tool in the box.)

I open the seacock--with minimal water intrusion--and lowered the metal rod to probe the thru hull for blockage. Pretty darn clever (IMHO) but no obstructions were found.

Acting on Bill's suggestion, I tightened the fan belt. The net result was a slight lowering of the operating temperature. I will still have the heat exchanger examined by the shop.

Stay tuned.

Mitchell Bober
Sunny Annapolis (where in February we exchange the heat for cold) MD

[Ed Haley]

Hi, Mitch:
I'm not sure if you are aware of it but many Universal Model 30 engines had this problem - they would overheat. Universal engines then recommended a heat exchanger change from the 2 inch tube to the 3 inch tube. I have the same boat as yours and the change was made before I bought it. I've never had a heating problem (knock on wood) and the change may be the reason.

My only concern is that the problem seem to suddenly come up. This suggests a blockage somewhere such as Cathy indicated - barnacles or something.

Hope you get the problem solved soon.

Ed

[Tom in Cambria]

I've been down at the boat for fur days and just got back. Many good suggestions already, but I can add a couple of thoughts having just been through this. One is that the strainer cap that goes over the water intake needs of have each hole drilled out when you paint the bottom. It's somethng like an eighth or three sixteenths drill bit that fits in the holes. After you paint it with bottom paint you have to drill out each little hole as the thick bottom paint can close those things down, but you probably know that since you've had the boat for awhile.

The next thiing is to chec k the Y fitting where the water dumps into the exhaust system after it goes through the heat exchanger. Those things do get carboned up. You just pull the hose off and stick a screwdriver or rat tail file in there and make sure it's clear. While you've got the hose off, start the engine for just a minute and see what kind of flow you have coming out of the heat exchanger. It should be a pretty robust stream that squirts a stream. If you have good flow there, that eliminates the raw water impeller and the heat exchanger as possible causes.

If you've had the coolant loop open anywhere (such as checking the thermostat) you may have an air lock in the top of the water heater. This is a very common overheating problem. If you have an airlock the expansion tank won't ger hot like it usually does. When the engine heats up and the thermostate opens just put your hand on the outside of the expansion tank. It should be so hot that you can only hold it on there for a few seconds. If it's warm but not really hot, you've got an air lock in the water heater. Take the forward hose off the expansion tank and blow into it with the cap off the expansion tank until you hear bubbles coming up through the tank. You may have to add coolant once you clear the air pocket out of the heater.

And finally the coolant pumps do eventually go bad on all engines. We're not talking about the raw water pump that is shaft driven here, we're talking the coolant pump that is belt driven which is below the thermostat. I had to replace mine once.

Look at it this way is there isn't something wrong inside the engine such as a head gasket or cracked block etc., then only two things can cause overheating. 1. Lack of circulation of the sea water 2. Lack of circulation of the coolant.

Both of these can only be caused by one of two things: 1. Bad pump 2. Blockage somewhere such as air lock in coolant in water heater. clogged heat exchanger, carbon build up in Y fitting, crimp in hose, bad thermostat, collapsed hose, restricted water intake, or restricted water exhaust, etc. You just have to work your way down each system until you figure out where the flow stops.

BTW you probably know there is a diagram of the two loops in the parts manual. I took colored pencils and colored my manual so I can see how the flow goes.

Good luck and let us know what you find.

[M. R. Bober]

OK. I have--finally--removed the heat exchanger. Assuming that it IS the problem (I am still unsure) I have a few options:
1) The radiator shop will overhaul the unit for ~$175.
2) A new replacement is ~$300+.
3) A new aftermarket "exact fit" is available for ~$225.
4) The 3" unit is ~$500.

Your thoughts, please.

Mitchell Bober
Sunny Annapolis (where the "Annapolis Radiator Repair Co" doesn't repair radiators any longer, but kept the name), MD

[Ed Haley]

I would install the larger heat exchanger since the smaller one wasn't sufficient to remove the heat from the system in the original configuration. I realize that this is the more costly decision but you do want to correct the problem as suggested by a Universal upgrade notice.

If you're not sure that the problem was associated with the heat exchanger, I hope you don't end up using a "hit and miss" procedure to solve it. You should be reasonably sure that the heat exchanger is the source of your troubles and not blockage in the raw water cooling system.

[Bill Cochrane]

Mitch, I'm not familiar with the universal heat exchanger, but most should be similar...a bundle of tubes that go inside a rectangular or tubular chanber. Raw water goes one way, coolant the other; one inside the small tubes, the other in the chamber. Heat is exchanged through the wallls of the small tubes. Normally the problem is that the tubes are clogged on the inside, or deposits built up on the outside. If the problem is inside, they can be "rodded" out with a wooden dowel close to the tube ID. The other way to clean it is to "boil" in a caustic solution to disolve the crud, kind of a super LimeAway.

You should be able to see if the tubes are clogged or have deposits on the outside. If they are pretty clean, chances are the heat exchanger is working. It still may be too small, but if the engine has performed in the past without overheating, I'd look elsewhere, especially before dropping $500 on a new, larger model.

If it is crudded up (technical term), then I'd check around at some automotive radiator shops and see what they'd charge to boil it. Shouldn't be anywhere near 175 bucks; of course, that may include disassembly and some new gaskets/fittings, so it may not be so bad; on the other hand, if the rubber parts are in good shape, you can pull the core yourself.

Or none of this is correct since your heat exchanger is not like mine on the Perkins.

I'd try the cheap route, though, especially since you're not sure where the problem lies.