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Overheating twin 224bs Closed system

D

diaquint

New member
"I have twin 190 L4 Merc's

"I have twin 190 L4 Merc's (1985)with a closed cooling system that I've been having trouble diagnosising. I'll give the symptoms and a little history and hopefully someone can help thru the fault tree.
Last year my starboard heat exchanger's coolant looked rusty, previous years the coolant looked great. So at the end of the year I drained both the fresh water and coolant section of the heat exchanger. This year when I went to fill-up the closed coolant side, the coolant was leaking out. I seen it leaking from the outdrive, at the fresh water inlet. I filled up the tank with water and ran for a while and all the water leaked out and the engine overheated. I then pressure tested the system and found out that the heat exchanger was leaking internally, linking the fresh water with the closed coolant side. I pulled the end caps and found out what tube was leaking. I had that tube welded, replaced the rubber seal and stoned the end caps and the heat exchanger's ends to make sure it was flat.
I ran the engine on land with water to the outdrive inlet for a while and all seemed to be fine until the boat was in the water, idling to my slip. It then over heated when idling. My question is, by closing up only one tube on a 4" heat exchanger, would that cause overheating?


My second problem is on my port side engine. I had the same problem, always losing coolant when sitting. I would fill-up the resevoir, start the engine and criuse without over heating. Once the the tank was full it wouldn't lose water utill I stopped for a while, eventually losing the water out of the lower units intake. But I could fill and again run until I stopped for a while.
After I had the starboard heat exchanger tube fixed and it didn't leak, I then fixed the port side the heat exchanger the same way. After it was fixed and the tank filled, I noticed I had another leak coming from the exhaust at the transom outlet. I refilled the and hooked up a hose to the water inlet on the lower unit. When I did that water immediately poured out of the gimble area, and also the cyclinders filled up with water. First time that ever happened. Obviously the engine oil turned milky. I ran some block sealer thru the closed system and the tank seems to hold but as soon as I hooked up a hose to run water thru the inlet, the cyclinders again filled up. The first time the back two cyclinders had water in them and the second time the front two cyclinder had water. I would imagine that the exhaust manifold is filling up and whatever exhaust valve are open is where the water goes. Since then I pulled my exhaust elbow/tank and noticed the gasket was leaking from the coolant side to the exhaust, and possibly from the exhaust elbow (fresh water to the exhaust). Could this cause the water in the cylinders when the muffs are on?

Some more history:
*Heat exchangers both sides getting hot to touch
*Exhaust elbow/tank both sides very hot at an idle

I could really use some help on what steps to take next!!"
 
"It sounds like you have a bun

"It sounds like you have a bunch of issues.
I would first take off the manifolds and elbows and the heat exchangers and have them all pressure tested. You may need to have them repaired or replaced as required.
Are you sure you are getting enough cooling water from your drive leg impellers? The exhaust elbows should not be that hot.
I am guessing you operate in salt water and that your manifolds are part of the FWC system?
In salt water the parts exposed to the salt water can corrode very fast if not flushed religeously after each use. This would include the exchangers, elbows and manifolds (if not FWC'd).
Rod"
 
"Don: On the starboard engine

"Don: On the starboard engine, how many tubes are in the exchanger? If you had five and lost one, that leaves you with a loss of 20% of its cooling capacity. I think it may just be due to a worn impeller in the OD leg. Did you chemically clean the engine cooling system before refill?

On the port engine, the bad gasket appears to be the problem of water entering the cylinders. Does the impeller need chaging on this OD?

Heat exchangers will have a hot inlet of coolant and a less hot outlet of the same. The water side will have a cool inlet and a warmer oulet.

Exhaust manifolds and risers should not be hot. Both engines are obviosly not cooling properly which may be from the worn impellers and would also produce hot manifolds from a lack of sufficient water flow.

I would replace both impellers and thermostats and clean/flush the engines. Pull both risers, inpect them for blockages, cracks and/or rust-thru and have them acid cleaned. Inspect both exhaust manifolds for blockages, cracks and/or rust-thru and consider having them acid cleaned if there is a build up of rust and lime deposits. Also important, inspect the exhaust flapper while the risers are off. Put them back together and see if she floats."
 
"I doubt losing one tube is th

"I doubt losing one tube is the problem. The exchangers I have seen have many small tubes; they look like 1/4" OD copper tubing to me. I don't know the actual number, but there must be 30-40 or more. So losing one would not likely make a noticable difference.
But having them all scaled up with salt and crud on the inside will certainly kill the heat transfer.
Rod"
 
"Thanks Guy, and Rod!!

As

"Thanks Guy, and Rod!!

As far as checking the drive impellers, I did pull the plug of both heat exchangers and started the eingines to see if I had flow, and it seemed to come out with a lot of force. Is there a procedure to measure?


Guy, I think you are right on why I was getting water into the engine. I believe the gasket was bad between the tank / heat riser and exhaust manifold. When I pulled the tank off the gasket just crumbled. My question is the best way to flush the engine? I tried pulling the oil pan plug off but it is frozen solid as if it were welded. What I've done is run a flush thru the engine and sucked out the oil thru the dipstick with a pump. Once all the oil was out I poured in new oil quart by quart and removed it again thru the dipstick but it seems that I can't get al the milky oil out. Any suggestions??

As far as the heat exchangers, ther are many tubes, probably 30 or more. So plugging one on each probably doesn't reduce the % of cooling to much. But one thing that has been troubling me or maybe I messed-up, since I reinstalled these heat exchangers. It seems that the output of these tube are in three sections, separated by two coppers stands at the end by the caps. The brass stands extend from the top diameter to the bottom diameter of the exchanger (probably for support). The only thing is, when I was testing each tube for leakage, I don't remember how these sections get linked together. I'm not sure if the hieght of these stands extended all the way to the caps or rubber gasket. Maybe there needs to be a space between the cap/gasket and the copper stands for clearance so that lake water flows from one section to another.I'm wondering if when I stoned the ends to make them flat, I may have closed off flow from one chamber to another. The rubber gaket is one piece with no cut-outs. Maybe I'm only flowing thru one section of the exchanger while the other tubes are sitting with no flow from the impellers. I'm not sure how these are designed. So any help would be appreciated. Sorry for all the questions but I'd really like to get this boat running before the 4th."
 
"I've uplaoded a picture o

"I've uplaoded a picture of the heat exchanger end that I'm referring to in my above note.<center><table border=1><tr><td>http://www.marineengine.com/discus/icons/mime_msword.gif""" align=left alt=""application/msword"">heat exchanger
[url=""][b]heat exchanger.doc[/b][/url] (36.9 k)</td></tr></table></center>"
 
"DJ;
At idle you should see a

"DJ;
At idle you should see about 3-4 GPM of water flow from the impeller pumps, so you should measure it to make sure that is about what you have.
I have only seen exchangers for V-6's and V-8's.
What are the two connections off the right side? Is the top one with the 90 deg bend the raw water inlet? What about the other?
Is the engine coolant on the shell side like most are? In other words, is the engine coolant on the outside of the small tubes, and the raw water on the inside of the small tubes?
What do you mean by: "...I stoned the ends to make them flat..."?
If you have a make and model for the exchangers it may be wise to contact the manufacturer to see how the partition baffles are supposed to be set up. It looks to me like these may have three back and forth tubeside passes (raw water), and if the baffles are not in place correctly, it will not work right.
Rod"
 
"To get the milky engine oil &

"To get the milky engine oil (watered down oil) out of the engine, you need to change the oil and filter then run the engine briefly at idle to warm it. Then drain the oil and change the filter again several times while running the engine to warm the oil and evaporate the moisture in it."
 
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