1980 Merc 260 I/0 overheating problem

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  #1  
Old 09-03-02, 04:54 PM
JAllen72
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1980 Merc 260 I/0 overheating problem

My 1980 Merc 260 I/O is not getting enough water to engine for some reason. I replaced impellor in lower unit, installed new water pump and thermostat and the impellor appears to be working properly however doesn't seem to pump up enough water to fill engine for cooling purposes. I checked the inlet hose at the engine and it is cool but all other hoses are hot when running. I am running engine out of water with a test thinga magiger to run water to lower unit. This engine does not have an additional pump as some do I guess. There is some water circulating but not enough any suggestions would be welcome. Thank you in advance. Jim


I would like to add that when running afer a while the exhaust turns white and the amount of water coming out at propellor is a small stream. There is some additional hot water coming out behing bell housing area. Running temperature is between 180 and 190 so I shut it down.
 

Last edited by JAllen72; 09-04-02 at 06:50 AM.
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  #2  
Old 09-04-02, 08:01 AM
Mr. Kiss
Join Date: Jan 2002
Location: SW Chicago, IL USA
Posts: 87
J,
Sounds to me like your engine cooling system has probably ingested more than one impeller over the years and is plugged. The white smoke you see is steam and if you don't want a MAJOR repair bill I suggest not running it untill it is repaired.
Hot water from the bell housing area may mean you've alread done major damage.

Your best bet it to try back flushing the cooling system and before I can help there I need to know a couple things...
Are you in fresh or salt water?
 
  #3  
Old 09-04-02, 01:44 PM
JAllen72
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It is possible that this boat has ingested an impellor or two, I do not know as I recently purchased this boat. I have been very careful not to run the engine for any extended period of time as I do not want to cause major damage. About 3 minutes max. as for the temperature of the hot water I would guess about 120 as it is about the same temp as my hot water in water heater. Not hot enough to burn but pretty warm. I am in fresh water to answer you question. Thanks
 
  #4  
Old 09-04-02, 02:00 PM
Mr. Kiss
Join Date: Jan 2002
Location: SW Chicago, IL USA
Posts: 87
Jim,
Are you in the water or trailered?
Do you own a service manual?

As I said before I believe you'll need to backflush the engine cooling system. I don't know a great deal about power boat engines as I mostly work on electrical and electronics. My guess without seeing your boat is that there is a water to water heat exchanger located somewhere after the water pump. They're usually shaped like a cylinder with hose fittings going in and out for fresh water and coolant. If you can pull the hose off of the output side of the freshwater section you can tell if the blockage is in the cooler or past it.

Where about are you located?
Larry
 
  #5  
Old 09-04-02, 02:37 PM
JAllen72
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Yes, the boat is trailered at this time and there is a cylinder shaped ( I think it is the power steering fluid cooler) located before the intake manifold. I do have a service manual but it does not refer to backflushing any where in it as I had thought that might be a good thing to do before, but I really do not know where to begin. I am located in Muskegon, Michigan.
 
  #6  
Old 09-04-02, 03:36 PM
Mr. Kiss
Join Date: Jan 2002
Location: SW Chicago, IL USA
Posts: 87
Jim,
What you need to do first is look in the manual for the heat exchanger fresh water input and output (the lake water), disconnect them and connect a garden hose to the output side and flush away.
 
  #7  
Old 09-08-02, 08:28 AM
JAllen72
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Well, the good news is it is fixed, it now runs at 140 degrees average. The only thing is I am not quite sure what I did , among many, that really did do the trick. I found no blockage of water in any lines anywhere. I did take off the lower unit and reinspect the impellor pump, I did find that there was not a cyntrifugal slinger at the top of pump, so I purchased one and a new o-ring for drive shaft. I flushed the system but the water flow was clean from the start. I found a couple of holes plugged at the inlet screens and cleaned them. My only guess is that I just wasn't getting enough water through hose to start with, changed filter in house (feel dumb on this one) much better flow of water to boat. At any rate I chauk it up to becoming very familiar with my boat, a good thing. But I would like to thank you for your imput. Have a great day, I am headed to lake Michigan! Jim
 
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