Engine temperature is 185F. I've changed the impeller, temp gauge, cleaned the heat exchanger, changed the thermostat and it just sits at 185F, removed any air at the top of the thermostat housing & hot water heater and "burped" the engine by revving it. No change.The underwater strainer is clear on the hull and water comes out the stern. Is the higher than specified temp (165F) something I should continue to be concerned about?
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A couple of stupid, obvious questions first
1. Did it run at 165 in the past? 2. Have you calibrated the temp reading, using a thermometer in hte water at the thermostat housing? 3. Have you veriified the thermostat temp? Tested? Is it installed correctly (not upside down)? 4. Is it steady at 185, meaning, is the system regulating to 185, or is it climbing up, and would surpass 185 with additional load? 5. Is there a restriction in the sea water side, like a clogged injection elbow? Did it ever eat an impeller, the pieces of which could be causing restricted flow? 6. Have you measured or otherwise evaluated the flow of sea and freash water?
1. Did it run at 165 in the past? 2. Have you calibrated the temp reading, using a thermometer in hte water at the thermostat housing? 3. Have you veriified the thermostat temp? Tested? Is it installed correctly (not upside down)? 4. Is it steady at 185, meaning, is the system regulating to 185, or is it climbing up, and would surpass 185 with additional load? 5. Is there a restriction in the sea water side, like a clogged injection elbow? Did it ever eat an impeller, the pieces of which could be causing restricted flow? 6. Have you measured or otherwise evaluated the flow of sea and freash water?
To John V.
This boat is new to me so I don't know if the M25 ever ran at 165. While I could put a thermometer in the the fill opening the temp will be different without the cap on. No broken impeller parts, a nice pulse of water comes out the stern and it seems to sit at 185 no matter what the load. The local service shop said it was okay but mentioned he could do an infared scan if I wanted. I could disconnect the sea water intake line, open the valve and try to blow the water out the strainer if that's physically possible.
This boat is new to me so I don't know if the M25 ever ran at 165. While I could put a thermometer in the the fill opening the temp will be different without the cap on. No broken impeller parts, a nice pulse of water comes out the stern and it seems to sit at 185 no matter what the load. The local service shop said it was okay but mentioned he could do an infared scan if I wanted. I could disconnect the sea water intake line, open the valve and try to blow the water out the strainer if that's physically possible.
M25 Temp
The only thing not mentioned is the age and condition of the hoses. You may want to consider replacing them, since you both have hit just about everything in your discussions. One other thing to check are the entry and exit points of the hoses on the HX itself. While the inside of the HX is usually the culprit, my experience is that the HX ports tend to get clogged too. I've had times when the inside of the HX is just fine, but one of the hose connections on the HX was clogged up over 50%! To clean them, I used a drill bit in my hand, and just worked through the crud. That alone brought the engine temp back down from over 180 to 165. (1986 M25 with the old 2 inch HX)
The only thing not mentioned is the age and condition of the hoses. You may want to consider replacing them, since you both have hit just about everything in your discussions. One other thing to check are the entry and exit points of the hoses on the HX itself. While the inside of the HX is usually the culprit, my experience is that the HX ports tend to get clogged too. I've had times when the inside of the HX is just fine, but one of the hose connections on the HX was clogged up over 50%! To clean them, I used a drill bit in my hand, and just worked through the crud. That alone brought the engine temp back down from over 180 to 165. (1986 M25 with the old 2 inch HX)
Stu's point is good
Stu is right, you chould check for flow everywhere. I fixed two overheating problems on two different boats in the last ten days, both of them sea grass clogs. The strainer didn't help. So, the hose COULD be clogged whil ethe heat exchanger looks good. Question 1 (for me): who makes a sea water flow sensor (and alarm), adn where can I get it? On the 185 temp., I suspect that the system is regulating to 185, since, as you report, it stays there no matter what. I assume you mean it warms up to 185, then regardless of load, idle to full power for an hour, it sits there. That's actually a good temp, since 165 is a bit cool for most efficient compustion, so I'm told. It would be good to know why it sits at 185, and if that is indeed the water temperature (calibration issue). To check, yes, the temp will be different with the cap off; but if you can run the engine with coolant flow at atmospheric pressure and get a good thermometer into the water near the gauge sender, you can find out if the gauge is right. With the same thermometer you can check the opening temp of the thermostat. jv
Stu is right, you chould check for flow everywhere. I fixed two overheating problems on two different boats in the last ten days, both of them sea grass clogs. The strainer didn't help. So, the hose COULD be clogged whil ethe heat exchanger looks good. Question 1 (for me): who makes a sea water flow sensor (and alarm), adn where can I get it? On the 185 temp., I suspect that the system is regulating to 185, since, as you report, it stays there no matter what. I assume you mean it warms up to 185, then regardless of load, idle to full power for an hour, it sits there. That's actually a good temp, since 165 is a bit cool for most efficient compustion, so I'm told. It would be good to know why it sits at 185, and if that is indeed the water temperature (calibration issue). To check, yes, the temp will be different with the cap off; but if you can run the engine with coolant flow at atmospheric pressure and get a good thermometer into the water near the gauge sender, you can find out if the gauge is right. With the same thermometer you can check the opening temp of the thermostat. jv
temp
John; Don't worry about the 185 degree temp. The hotter a diesel runs, without OVERheating, the better. Better fuel combustion, cleaner burning, less deposits, lower consumption, the list goes on.
John; Don't worry about the 185 degree temp. The hotter a diesel runs, without OVERheating, the better. Better fuel combustion, cleaner burning, less deposits, lower consumption, the list goes on.
Thanks to all
Last night I disconnected all hoses blew and cleaned everything. No noticeable crud anywhere. Restarted the engine and the temp gauge is a new tellfix. I think the whole problem is how to read the gauge. The numerals are between the divisions so if the needle points to a number then I guess that's the reading. If you go by the divisions it runs about 180-185. If you go by the numerals its closer to 170-175. Thanks again for all the assistance.
Last night I disconnected all hoses blew and cleaned everything. No noticeable crud anywhere. Restarted the engine and the temp gauge is a new tellfix. I think the whole problem is how to read the gauge. The numerals are between the divisions so if the needle points to a number then I guess that's the reading. If you go by the divisions it runs about 180-185. If you go by the numerals its closer to 170-175. Thanks again for all the assistance.
Ok for John but not OK if Raw Water Cooling
For those with raw water cooling with no heat exchanger, 180-185 is too hot. The salts in the seawater will precipitate out and clog your engine. I believe that something around 165 is the critical temp. This is why the raw water cooled Universal engines have 145 degree thermostats.
For those with raw water cooling with no heat exchanger, 180-185 is too hot. The salts in the seawater will precipitate out and clog your engine. I believe that something around 165 is the critical temp. This is why the raw water cooled Universal engines have 145 degree thermostats.
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