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Old 06-13-2013, 01:11 PM   #1
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engine temperature

My 2000 Mainship 390 has a single 300hp Cat engine. If I warm the engine up before leaving the engine temperature gauge stays at around 175 degrees which is normal. When I stop and then later restart the engine the temperature invariably climbs to over 200 degrees at which time I of course shut the engine down. If I wait a few minutes the gauge quickly drops back to normal range and I am able to continue on. I replaced the temperature regulator (thermostat) but the problem persists. The engine does not appear to me to be actually overheating. Both the upper and lower helm gauges give the same readings. Any suggestions?
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Old 06-13-2013, 01:24 PM   #2
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A few suggestions:
  1. Do not idle your vessel at the dock to warm it up. This is not good for the engine, especially Cat 3126s.
  2. Get an IR gun and measure around the engine such as circulating pump, heat exchanger outlet etc. Do this on a routine basis which will be a very good check against the temp gauges.
  3. Insure coolant level is to the Cat book mark
  4. How often do you change out the RW impeller?
  5. Have you done the 1000 hour Cat maintenance? If not to 1000 hours you may still be due - this will involve a coolant change
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Old 06-13-2013, 02:12 PM   #3
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When I stop and then later restart the engine the temperature invariably climbs to over 200 degrees at which time I of course shut the engine down. If I wait a few minutes the gauge quickly drops back to normal range and I am able to continue on. Any suggestions?
Suggestion: Your gauge/s may be reading "heatsoak" coolant, that is coolant that has picked up extra heat by not circulating when the engine was shut down. Instead of waiting at idle for the engine to come up to temp b/4 moving off (not real good for the engine) spend a few minutes idling b/4 you shut down instead. Let the coolant circulate for some time with no load then see if it stays there when you restart.
You may also have an air/steam pocket somewhere in the cylinderhead which superheats some coolant upon restart. You don't define "later" so hard to tell what is going on.
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Old 06-13-2013, 02:14 PM   #4
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sunchaser wrote;

"Do not idle your vessel at the dock to warm it up."

I think it's good to warm up for 2 or 3 min but 7 or 8 is a tad much.

Sounds like your engine coolant is being warmed by the warmer cylinder block as usual just after shutdown. The engine cools slowly and immediately after shutdown there's no coolant flow at all so the coolant in the block gets quickly heated slightly above it's dynamic state. If you restart soon but not immediately after you'll probably notice a quick cooling below normal idling temperature as the coolant has been sitting for a little bit in the heat exchanger next to the cold seawater. This is 100% normal. With proper anti-freeze your coolant can not boil and function normally well above 212 degrees because the pressure keeps the water/coolant stable.

With sufficient AF and pressure running an engine 225 degrees all day long is probably (more like definitely) something that can be safely done. With straight AF and 30lbs of pressure one could probably run 250 degrees. Some AF bottles have the boiling point listed on a graph along w the freezing point.
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Old 06-13-2013, 02:29 PM   #5
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I only let the JD engine idle for the time it takes to cast-off (2-3 minutes) and assuring water is flowing out the exhaust, and then idle (850 RPM) under load while heading for the marina's exit. Then run at "high idle" (1200 RPM) until engine warms. Don't run at cruise speed (1800 RPM) until engine's coolant rises to operating temperature (170-180 degrees).
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Old 06-13-2013, 04:52 PM   #6
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I didn't mean to give the impression that I let the engine idle at dock until it reached 175 degrees. I do the following as described by Mark Pierce in the previous post:

Let my engine idle for the time it takes to cast-off (2-3 minutes) and assuring water is flowing out the exhaust, and then idle (850 RPM) under load while heading for the marina's exit. Then run at "high idle" (1200 RPM) until engine warms. Don't run at cruise speed (1800 RPM) until engine's coolant rises to operating temperature (170-180 degrees)."

I've operated the boat for several years in a consistent manner and high temp readings after letting my 3116 Cat engine cool for a couple of hours is definitely a new problem. I appreciate the responses so far and you have given me several new valuable ideas to explore. Could it be a faulty temp. sending sensor?
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Old 06-13-2013, 05:23 PM   #7
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Two hours .... Ten hours ... Makes no diff. What has it done in the past?

Engine temp is not coolant temp. Many of the major parts of your engine aren't heat soaked when the coolant reaches it's normal stabilized temp. Small air cooled engines will heat soak much faster and 2strokes faster than that. Large lightly loaded engines take much longer. How much? I'm guessing if I say 30 min to an hour but that's all I can do.

Exhaust valves and piston crowns will heat soak much faster than oil pumps and crankshafts. Speaking of oil that is probably the best gauge of when an engine is heat soaked but some parts still aren't heat soaked yet.

My engine attains a temp gauge reading of 185 degrees after only a few (3 or 4 min) of running at an idle.
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Old 06-13-2013, 06:32 PM   #8
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Quote:
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is definitely a new problem.
IMHO:

The Cat 3116/3126 engines are very sensitive to overheat issues. The 300HP model is a gem as compared to the higher HP versions. But any unusual heating issue, especially on a 13 old historically trouble prone marine engine should be looked at by Cat with servicing done by the book. I'd be wary of general internet advice and use the services of a Cat marine technician instead.

As I said, IMHO
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Old 06-13-2013, 08:15 PM   #9
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... Engine temp is not coolant temp. Many of the major parts of your engine aren't heat soaked when the coolant reaches it's normal stabilized temp. ...
That's why I don't go to "hard cruise" (2200 RPM, engine rated for 2500 but governed to 2400) until at least a half-hour of operation.
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Old 06-13-2013, 08:22 PM   #10
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I've operated the boat for several years in a consistent manner and high temp readings after letting my 3116 Cat engine cool for a couple of hours is definitely a new problem. I appreciate the responses so far and you have given me several new valuable ideas to explore. Could it be a faulty temp. sending sensor?
"Cool for a couple of hours" = forget my suggestion about heat soak or air pockets.
I agree that this could result in a severe problem if left unattended on this model engine.
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Old 06-13-2013, 09:56 PM   #11
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I agree w Brooksie at this point re the temp issues. Now there is as far as I know two common marine engines that have chronic overheating problems. Is there any more problematic engines?

Mark you should get your governor adjusted for 2600 (approx or a bit higher) so you can test run your engine for proper loading. You should know that your prop is limiting your max eng rpm (in gear) and not your governor. Get the governor adjusted and then adjust your prop to a WOT eng speed of 2500rpm. Then set your cruise to something a bit less than max cont power as defined by JD. Please consider this just a suggestion and from a friend ... not an engineer.

After thinking about this a bit I think perhaps you should pass this over the desk of a JD engineer or equivalent. Judging by your wake in your pics you're obviously running the Coot fairly hard and considering your post you MAY ... just MAY be running only 200rpm down from max WOT rpm (2400). You don't know. Only 200 down may be running too hard depending on how your engine is rated. Max WOT rpm COULD be 2700 free of the effect of the governor . You don't know because your governor won't let you find out as it stops your engine from going faster than 2400rpm. You'd be 200 rpm under propped in that case and in that example you would not be over propped at all. But you could be running good rpm and be underloaded ... but next to impossible for you to be underloaded making as much wake as you do. I'd sure want to know.
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Old 06-13-2013, 10:05 PM   #12
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Eric, 2200 RPM accomplishes hull speed. I'm not looking for anything more (fuel consumption jumps over the roof). Besides, the JD is not a high-revolution, Japanese engine.
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Old 06-14-2013, 07:01 AM   #13
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Mark you should get your governor adjusted for 2600 ... but next to impossible for you to be underloaded making as much wake as you do. I'd sure want to know.
Would you mind expanding (explaining the reasoning) on the individual points and suggestions contained in that post?

It was a fairly comprehensive collection of cause and effect items that bear further explanation.
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Old 06-14-2013, 10:20 AM   #14
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How do you know what RPM you are running? Have you had the tach calibrated recently. I would also consider an electrical issue between the gage and the sender.

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Old 06-14-2013, 10:33 AM   #15
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Mark,

"high rpm Japanese engine"?

What's it's skin color Mark? It is what it is .... a 2500rpm engine. I'm just saying it's not a good idea to have the governor speed below the rated rpm. You can't prop the engine or determine it's correct loading. The purpose of the governor is to insure you don't get much over your rated rpm to protect the engine from over speeding. You could be over propped or under propped. How would you know?

I just went back and read your posts. I thought you were cruising at 2200. I see it's 1800. What is your max rpm in neutral gear? What is your max rpm in fwd gear?


Re Rick's comment "bear further explanation."

Of course I know you know all the power loading stuff so I assume you think I have not made myself clear or have made a mistake. Or from your words have left something out ... just omitted an important point. The important point I hoped to have made is that if Mark's max rpm is 2400 he may not know if it's the prop size that's limiting the engine speed or the governor. I think one needs to know that.

Been through this 100 times in the past and still there seems to be many that don't understand the loading issue. Many don't care and just wish I'd shut up but I'm sure there are many more that are trying to learn and understand.
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Old 06-14-2013, 10:44 AM   #16
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Could it be a faulty temp. sending sensor?
I was told by a Cummins guru that if the temp sensor is insulated from the housing it screws into (plumber's goop, teflon tape. etc.) it cannot make a ground and the temp gauge will read high on your panel. If that sensor has recently been changed, that might be a place to look. (Easily done.)
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Old 06-14-2013, 11:29 AM   #17
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Mark,

"high rpm Japanese engine"?

What's it's skin color Mark? It is what it is .... a 2500rpm engine. I'm just saying it's not a good idea to have the governor speed below the rated rpm. You can't prop the engine or determine it's correct loading. The purpose of the governor is to insure you don't get much over your rated rpm to protect the engine from over speeding. You could be over propped or under propped. How would you know?

I just went back and read your posts. I thought you were cruising at 2200. I see it's 1800. What is your max rpm in neutral gear? What is your max rpm in fwd gear?


Re Rick's comment "bear further explanation."

Of course I know you know all the power loading stuff so I assume you think I have not made myself clear or have made a mistake. Or from your words have left something out ... just omitted an important point. The important point I hoped to have made is that if Mark's max rpm is 2400 he may not know if it's the prop size that's limiting the engine speed or the governor. I think one needs to know that.

Been through this 100 times in the past and still there seems to be many that don't understand the loading issue. Many don't care and just wish I'd shut up but I'm sure there are many more that are trying to learn and understand.
Eric, I fully understand what you are saying and fully appreciate the need to be properly propped. High speed high performance diesels definitely need to be properly propped since they are usually loaded up the whole time. You don't want them to be overloaded. Not only are they loaded up, they are pumped up with turbochargers and putting out a LOT of power for the amount of displacement(in the engines...not the boat). But I do not believe it to be that big of a deal if it is a slower turning NA diesel that is not operated anywhere near it's rated load....in this case 1800RPM on a 2500RPM engine(BTW...I would not necessarily consider that slow turning).

With that said, and I am going outside of my knowledge base here....if his governor was readjusted, would that not be like de-rating an engine? And if that is the case, would you not prop the boat to match the new rating??? These are somewhat rhetorical questions as I am not sure of the answer....I will start a new thread so we don't go to far off here....
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Old 06-14-2013, 11:34 AM   #18
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Have no burning desire to mess with governor and propeller. The boat achieves hull speed at 2200 RPM, but the majority of time I go at a much more economical 1800 RPM a knot slower. It "works" for me.
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Old 06-14-2013, 11:48 AM   #19
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John,
I think that all engines should be properly propped but I agree w you that older engines like Perkins and Lehmans aren't quite as sensitive to miss-handling as high output engines like your Yanmars on the Mainship.

John wrote; ".if his governor was readjusted, would that not be like de-rating an engine?" No. But I see where you're trying to go. If mark adjusted his governor to 2000rpm his engine would not develop the power that is claimed for that engine because he couldn't get above 2000rpm. But the rating would remain the same at all engine speeds below and at 2000rpm. The engine would just be "hobbled". By just adjusting the governor full rated power will be restored if the engine is loaded/propped right.

I see no justifiable reason not to prop an engine correctly.

Mark, I don't know how to adjust a governor and I assume you don't either. I assumed you would have your mechanic accomplish that.
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Old 06-14-2013, 11:59 AM   #20
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John,
I think that all engines should be properly propped but I agree w you that older engines like Perkins and Lehmans aren't quite as sensitive to miss-handling as high output engines like your Yanmars on the Mainship.

I see no justifiable reason not to prop an engine correctly.
I agree. But some would argue that overpropping a boat down a few hundred RPMs from rated power would net them a better cruise speed at lower RPMs(ie bigger load at lower RPM). I do not believe it to be a good practice.

BUT....I have started a new thread to discuss this so we don't get too far off topic and we can get back to providing the OP with some help!!!

http://www.trawlerforum.com/forums/s...tml#post162827
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