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Old 07-05-2017, 06:18 AM   #1
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Overheating 101

Been running my new to me boat for a couple of months and everything engine-wise has sounded and looked good. Ford Lehamn SP135's which I run at 1500-1700 max. Both engine temps show at 180+- and oil pressure at 55. Port engine always reads a little higher, less than 5 degrees. Yesterday I decided to open it up and check out cooling temps at WOT. When I did the temps went to just under 200 on starboard and 200 on port. Took 3-4 minutes before I got an alarm which I assume was overheat on the port side. Throttled back and in a minute or two alarm cut out, temps dropped to normal and everything back to normal on the 1.5 hour cruise back home.

I assume this was caused by diminished water flow in coolant system as everything returned to normal when I backed off RPM's. Does a RW pump either work or not work, no in-between, for the most part?

Checked coolant levels in overflow tanks and both were fine.
No leaks or anything to note.
Strainers were cleaned 15 hours ago.
Impellers changed 6 hours ago.
New heat exchange/oil coolers, RW pumps 3-4 years ago before previous owner cruised loop and Bahamas.

My thought (inexperienced and little knowledge) is to flush raw water system with Barnacle Buster or similar although I haven't opened HE to see how clean/dirty they are yet. Looking at everything else in and on the boat/engines I believe they will be pretty clean but not sure.

Know this is all simple stuff for you guys and I would think that this situation is pretty normal or frequently heard. Have the standard engine alarms, nothing added. Is there an audible alarm difference between port overheat, starboard overheat or port/starboard oil pressure? Alarm goes off, just figure it out with the gauges?

Thanks for any comments.
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Old 07-05-2017, 06:35 AM   #2
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Greetings,
Mr. fb. What is your RPM at WOT?
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Old 07-05-2017, 06:43 AM   #3
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dont be surprised if you find impeller blades and even a broken zinc or two in the inlet side of the heat exchanger.
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Old 07-05-2017, 07:03 AM   #4
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FL135's show a rating of 2600 RPM's at WOT. I have original props on the boat and clean bottom when this happened and was slightly less than rated RPM's, 2500 or so.
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Old 07-05-2017, 07:03 AM   #5
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If you have not cleaned your heat exchangers and oil coolers in 4 years I would suggest you start with that. The Barnacle buster may work but I would want to see how the exchangers look.
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Old 07-05-2017, 07:07 AM   #6
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Quote:
Originally Posted by what_barnacles View Post
dont be surprised if you find impeller blades and even a broken zinc or two in the inlet side of the heat exchanger.
Yes, will open the HE's up at first opportunity. Hope is is that simple, some bits and pieces. I did replace the impellers and zincs but nothing broken although it would seem to be hard to tell with a zinc. I'm not a WOT guy but just wanted to test out the cooling and make sure all was well and then go back to living a happy life at 1600. I think I am glad I did this??
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Old 07-05-2017, 07:11 AM   #7
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If you have not cleaned your heat exchangers and oil coolers in 4 years I would suggest you start with that. The Barnacle buster may work but I would want to see how the exchangers look.
Thanks. I can't find anything that indicates any service done since they were installed new. Will open them up and see. Only 3-4 years old so I would assume that they should be in good shape physically and just need a cleaning. That's not much age on these, correct? Zincs were replaced regularly...
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Old 07-05-2017, 07:17 AM   #8
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Greetings,
Mr. fb. "I think I am glad I did this??" You rebel you!

You say impellers were fine BUT what about bits that may have broken off previous to your ownership and still lodged in ?? places. Probably a ways down the analysis list but still a possibility. Just something to keep in mind.

I think your step by step inspection of the cooling system is warranted starting with the HE. Not a big deal to remove the end caps AND it's service experience that you can file in the memory banks. If nothing else, you're becoming more intimate with your mistress...

One more thing I will add. When you change zincs in the HE, put wrenches on BOTH the HE nut and the zinc holder. If you wrench on the zinc holder alone you may break the solder seal holding the nut on the HE. Don't ask how I Know...
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Old 07-05-2017, 08:03 AM   #9
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Yes, quite the rebel. At least that what all my sailboat friends say...! I would think that running WOT for 15 minutes every 50 hours or so would be an ok thing to do. Not so much for cleaning out cylinders and all that but to check cooling just like I did? No? I think I read that these engines have little need for high RPM "cleaning out"?

Thanks for the tip on the zinc install. I just wrenched them in never thinking about the solder seal (saying it like he actually knew anything about a solder seal). Also was SO proud to change the impellers all on my own just like a big boy I didn't think about needing to open up heat exchanger to check as nothing seemed amiss. Or aMrs. Either way. Now that I am learning a bit more I see the need to go back and look at several things no matter how pretty they are on the outside.

Going to hijack my own thread but the other thing I am trying to fix is the dipstick accuracy on my engines. I believe that the angle of the engines leads to the oil showing as low when it really isn't. Will mark it accurately when I change the oil in another 50 hours or so but for now I am showing this level on the pic. Both engines the same. Is this an adequate level for operation on the FL 135's? It seems you have the same ones maybe? Thanks for the comments.
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Old 07-05-2017, 08:16 AM   #10
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You are correct, 101 digging wise to do. Do you know the last time coolant was changed? Also - Original props are no guarantee for correct props. The over heat alarm is an indicator of an issue whether exhaust elbows or ?? Some will argue, but too much prop can lead to full throttle over heat. While you're at it, check tachs against a photo tach.
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Old 07-05-2017, 08:20 AM   #11
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Is the bottom and props clean ?
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Old 07-05-2017, 08:36 AM   #12
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"Been running my new to me boat for a couple of months and everything engine-wise has sounded and looked good"


New to you boat after a couple of months perhaps consider these possibilities for a slower overheat at higher loads....
- Are the thru hulls loading up with growth
- Are you suction hoses new (thru hull to water pump hoses)
- Impeller is weak
- Impeller cam worn
- Blockage in one or more coolers
- Exhaust partially blocked
- Weak belt(s) on coolant side pump
- Thermostat(s) hung


Since it seems to affect both engines you can likely mostly rule out some of these by looking at the maintenance records and work most likely to least likely.


Additionally contributing factors could be engine related but you have not mentioned smoke or soot or water sheen at higher rpm so far.
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Old 07-05-2017, 08:40 AM   #13
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You are correct, 101 digging wise to do. Do you know the last time coolant was changed? Also - Original props are no guarantee for correct props. The over heat alarm is an indicator of an issue whether exhaust elbows or ?? Some will argue, but too much prop can lead to full throttle over heat. While you're at it, check tachs against a photo tach.
don't know of last coolant change and haven't learned how to check it to see if it needs it. A way to test the % of coolant left or something? Need to read up on how-to do that.

I will go back over the old receipts but I believe the exhaust elbows were also replaced when PO got ready to cruise. He did me some favors back then and didn't spare much $$$ getting ready. Just got a photo tach but couldn't use it this weekend as it was just wifey and me. I don't like going in engine room while running if there is nobody there for me to yell to. I know it looks relatively safe but I can't see waves, don't know whats going on and no way to contact anyone except cell phone maybe. But I bet you guys figured that out years ago....

I did check the props and they are the original ones designed/sized for the boat. Took off the 4 blade props as I have no business cruising around overpropped. Engines would only get to 2200 rpms with those. Had vibration which led me to have diver check props and they were not in good shape so had the originals, which were on board, tuned and balanced and then put back. Then had the same done to the 4 blades for spare. Nothing like an unplanned $2400 spend but hey it's only boat dollars right? Not like it is real money or anything....
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Old 07-05-2017, 08:41 AM   #14
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Is the bottom and props clean ?
Yes, everything cleaned about 2 weeks ago. Have it done monthly....
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Old 07-05-2017, 08:46 AM   #15
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Quote:
Originally Posted by smitty477 View Post
"Been running my new to me boat for a couple of months and everything engine-wise has sounded and looked good"


New to you boat after a couple of months perhaps consider these possibilities for a slower overheat at higher loads....
- Are the thru hulls loading up with growth
- Are you suction hoses new (thru hull to water pump hoses)
- Impeller is weak
- Impeller cam worn
- Blockage in one or more coolers
- Exhaust partially blocked
- Weak belt(s) on coolant side pump
- Thermostat(s) hung

Since it seems to affect both engines you can likely mostly rule out some of these by looking at the maintenance records and work most likely to least likely.


Additionally contributing factors could be engine related but you have not mentioned smoke or soot or water sheen at higher rpm so far.


Thanks for a to-do list on this. Will start at top and work down. Water hoses appear brand new to almost brand new. No smoke to speak of at startup or running. Barely see a little for the first few minutes after starting. My wife saw none but I did is how little there is.

What temp should I be running at WOT? I would expect it to go up some but not sure what that should be. If I remember my reading correctly it seems that under 200 OK, over 200 and I need to do something immediately? If everything is working correctly should it stay at 180 or so?

Last, what would cause both engines to do this at the same time? Separate systems completely....maybe the same lack of good maintenance/cleaning of cooling system on both?
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Old 07-05-2017, 09:06 AM   #16
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Greetings,
Mr. fb. "...maybe the same lack of good maintenance/cleaning of cooling system on both?" OR both systems are clean and in the same condition AND you have yet another problem....In other words, I have no idea.

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Old 07-05-2017, 09:46 AM   #17
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"Last, what would cause both engines to do this at the same time? Separate systems completely....maybe the same lack of good maintenance/cleaning of cooling system on both?"


There are a number of things that tend to happen over time with both engines in a twin.
- thru hulls loading up with growth
- poor impellers (cracking vanes, soft from winterizing chemicals, etc)
- rwp cams being 'worn'
- buildup on raw water side of ''coolers''
- Silicate and impurity buildup on coolant side of X-changer
- Exhaust restrictions due to older/failing elbows

To mane a few.


"What temp should I be running at WOT? I would expect it to go up some but not sure what that should be."


Most of the boats I have owned the temps do not go up any from a fully warmed engine to WOT. On the ones that had some creep it was very small.
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Old 07-05-2017, 02:11 PM   #18
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I have owned boats where the temps at low load were thermostat controlled but went up a bit at high load. sear water temps can make a difference.

If you have an engine heater water heater don't be surprised if that side is a little lower at above tstat temps.

On a new to you boat a full cooling system inspection is a good idea so you know where you are. Junk in the HE is common. Chemicals are not the answer only opening and inspecting and cleaning.
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Old 07-05-2017, 02:45 PM   #19
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The fact that you put original props back on does not alter the fact they could be too big. This will indeed affect both engines. Sounds like the PO intentionally over propped with the 4 blades.

Ascertain full rated book RPM. Then armed with your photo tach, can you achieve that number? ( if only for 15 seconds so you don't set off alarms again) If yes, that is good. Now you can concentrate on the other noted over heat possibilities. If no, you have some decisions to make.
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Old 07-06-2017, 11:57 AM   #20
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Quote:
Originally Posted by firstbase View Post
Yes, quite the rebel. At least that what all my sailboat friends say...! I would think that running WOT for 15 minutes every 50 hours or so would be an ok thing to do. Not so much for cleaning out cylinders and all that but to check cooling just like I did? No? I think I read that these engines have little need for high RPM "cleaning out"?

Thanks for the tip on the zinc install. I just wrenched them in never thinking about the solder seal (saying it like he actually knew anything about a solder seal). Also was SO proud to change the impellers all on my own just like a big boy I didn't think about needing to open up heat exchanger to check as nothing seemed amiss. Or aMrs. Either way. Now that I am learning a bit more I see the need to go back and look at several things no matter how pretty they are on the outside.

Going to hijack my own thread but the other thing I am trying to fix is the dipstick accuracy on my engines. I believe that the angle of the engines leads to the oil showing as low when it really isn't. Will mark it accurately when I change the oil in another 50 hours or so but for now I am showing this level on the pic. Both engines the same. Is this an adequate level for operation on the FL 135's? It seems you have the same ones maybe? Thanks for the comments.
The line you show on your picture is about where I have marked my dipsticks after added the correct measured amount of oil.

Ken
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