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Old 03-03-2020, 09:35 AM   #1
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Block Heaters

My new to me boat has a pair of Cummins 6CTA Diamonds. The PO was running the boat for the sea trial. I noticed on the AC Panel "Block Heaters". I made mention of them to the PO on the sea trial and he scoffed at me....giving me the impression that they were either not installed or they didn't work. I didn't think much of it. Well when I got the boat home, I noticed that when I flipped the switch, the AC meter definitely indicated a load. SO I left them on and went about my day. I then went down in the engine room and lo and behold, they most definitely work. My long winded preface to my question:
What is your opinion of block heaters? Advantages and disadvantages? Cummins guru Tony Athens somewhat slams them in favor of a product he sells(oil pan heaters). He also claims that they have to be replaced often and that they use a lot of power.
Anyway, my thoughts are that their primary purpose is to keep condensation at bay and therefore keep corrosion at bay. Thoughts?
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Old 03-03-2020, 09:52 AM   #2
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Block heaters do use a lot of power, particularly if they're not thermostatically controlled. Having the engines warmer at startup should make them easier to start, give a bit less smoke and cause a bit less wear. They'll also have the engines ready to accept heavy load sooner, as they'll need less time to get up to temperature.

Ideally, you'd heat both the coolant and the oil before startup for best results.

In hot weather, there's probably not a huge benefit to using them, although they might come in handy for those times when you want some extra load on the generator.
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Old 03-03-2020, 09:59 AM   #3
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You live in Texas! You don't need them. Nice to have but until you do the Loop and find yourself in Nova Scotia in October forget about them.

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Old 03-03-2020, 10:03 AM   #4
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You live in Texas! You don't need them. Nice to have but until you do the Loop and find yourself in Nova Scotia in October forget about them.

pete
We have 30 degree temps followed by warm humid weather. The engines do not warm as rapidly as the air...so there they are, below the dewpoint of the ambient airmass and it looks as if you have hosed your engines down....dripping wet with condensation. We get wild temp fluctuations in the winter down here that cause serious condensation. I realize that generally and theoretically block heaters were not designed for atmosopheric control of engine rooms...and were indeed designed for what you suggest. But down here it does not get cold enough for a healthy diesel to start. But yeah....a cold start is theoretically hard on an engine and you can prevent wear as stated above.
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Old 03-03-2020, 10:06 AM   #5
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With those kind of temperature swings, then it won't hurt to leave the block heaters on during cooler weather to keep the engines (and engine room) warmer and avoid condensation.
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Old 03-03-2020, 10:26 AM   #6
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Id leave them on for corrosion reduction. Either your built in ones of Tonys' Wolverine pad heaters.
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Old 03-03-2020, 10:31 AM   #7
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I have a block heater on my John Deere in the trawler, my "C" series Cummins in the charter boat, and my "B" series Cummins in my Dodge pickup. If the temperature drops below 50 degrees, I may turn them on for around 1-3 hours before starting the engine. Below freezing I definitely turn them on for 3-4 hours. Otherwise I don't use them.

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Old 03-03-2020, 11:16 AM   #8
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I'd guess you have immersion heaters like me, Kim Hotstarts in my case. These are simply a heating element like you'd find in a household water heater, mounted in a threaded port in your engine block. Mine are 250 watt and I run them on timers, 2 hours and off during cold weather. I've used them on my present Cummins and also 2-cycle Detroits for 20+ years with no ill effects. Keeps the engine room warm and dry too.
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Old 03-03-2020, 11:36 AM   #9
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I don't know the "right" answer, especially for the conditions you encounter. However, I installed the Wolverine oil pan heater on my Cummins 6BTA several years ago. When at dock (except when there is only 15 amp service available) it is always on. I do also have the standard block heater you are talking about.
For me, the Wolverine does the job well. It keeps the engine warm, drys out the ER, and keeps the ER warm all winter using very little power compared to what the block heater would do.

Around here in the winter, the relative humidity often goes to 95 plus % with air temps around 32 to 35 overnight. My ER is always about 50-55 degrees with about 50% humidity. (I have a temp/humidity sensor in the ER). I have almost no corrosion in my ER.
It works well for me.
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Old 03-03-2020, 12:17 PM   #10
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We loved the immersion heaters on our Detroits courtesy of the PO. We left them on all the time when at the dock in the cooler 6 months of the year. Keeps the engines a nice even temperature, the ER toasty and dry. A bonus on our old Hatteras was the dual walk-in engine rooms on either side of the lower companion way. We'd open the doors and it would keep the whole lower level warm. No need to run the reverse cycle AC and all its moving parts. Ours had a thermostat tapped into the coolant tank, an excellent feature and power saver. We'd turn them off before starting the engines.

I should note we used them the heaviest when we stopped cruising full time, though still living aboard here in eastern NC. There was awhile when we still had the boat once we moved back ashore, and we left them on when we were away from the boat, kept even the upper level in the 50's when it was in the 30's outside. You could accomplish this on a boat that had only hatch access to the ER.

I liked them so much I put a little Wolverine on the generator. Helped keep the generator/utility room warm and dry as well. However, it did not do as good a job as the others in keeping the whole block dry.
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Old 03-03-2020, 12:34 PM   #11
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You need to figure out what wattage they are. Some install heaters intended for arctic cold starts and can be like 1250-1500w. No need for those on a boat unless a huge engine. While most of those are controlled with tstats, not all are. And even with tstats, if both are on you are drawing a lot of power. Seen several boat fires caused by crappy shore cords plus the amps of block heaters.

You do want to control that condensation. Block heaters at 250w will do that just fine. One trick is to put in a 1000w heater designed for 240v, and run it at 120v. That gets you down around 250w or thereabouts. Or use a timer. On a couple hours, off for six, or something like that. As long as engine is above dewpoint, there will be no condensation inside or outside of engine.

I too live in an area with wide temp and humidity swings (SE NC), probably about the same as TX. Mostly fall, winter and spring. I have the same engine (but only one) and handle it differently. No block heater. If I know a warm front is coming through, I go to the boat and crank engine and gennie for about 15min to build up a little heat. Then the front comes through and both are warmer than the humid air. As the front is warm, the engine does not cool below dewpoint til next cold/warm front cycle. Works well as engine does not have corrosion on it after like 13yrs of doing this. Nice that the boat is very close to the house, so just a quick walk. Probably have to do this about 10 times a year.

Boat is in use all year round, so engine gets a loaded run at least once a month. Figure in TX you will be about the same.
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Old 03-03-2020, 01:29 PM   #12
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Ok so where are these things and how can I find out if they are thermostatically controlled?
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Old 03-03-2020, 03:16 PM   #13
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IF you run 2 stroke Detroits a block heater is really needed when the temps go below freezing.

Usually an hour or two of an immersion unit in the water jacket will have a Jimmy starting like you just shut it down.
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Old 03-03-2020, 03:30 PM   #14
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My first experience with block heaters was when I was involved with small boats at USCG Stations.


I believe they used them much of the time with the idea that running down to the boat for an immediate response required warm engines.


John, you may want to stop by the local USCG station and ask what they are doing.


My experience with block heaters in the assistance towing/commercial world was they were used whenever fairly quick response was needed or freezing engine room temps. My one boss like leaving them on till the dead of summer because of easier starts and less corrosion in the ER.


As pointed out, depending on what you have will determine some of the possibilities and benefits.
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Old 03-03-2020, 03:43 PM   #15
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In a tow boat or other "might need to go right now" situation I'd definitely want block and oil pan heaters running 24/7 even in the summer. The warmer they are at startup, the faster you can get the boat out of the slip and if needed shove the throttles forward without concern for damage.
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Old 03-03-2020, 03:56 PM   #16
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There may be other benefits beyond "go now"...not an engine guy so I would defer it to people who do use them al the time.
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Old 03-03-2020, 04:10 PM   #17
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Just an FYI. My Wolverine 250 watt oil pan heater cost about $75 and was an easy DYI install (as long as your ER has a 120V plug nearby). A very minor boat cost in my opinion. I still have the regular block heater installed (about 1250 watts), but I rarely use it, but it is there if I decide to use it. The constant 250 watt draw is minor, and with the ER vents closed over, is enough to keep the whole ER warm and dry.
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Old 03-03-2020, 06:23 PM   #18
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Ok so where are these things and how can I find out if they are thermostatically controlled?
Phillips-Temro Zerostart has all the info and fitment graphics you need, plus good tech advice by phone.

It's not all about starting the engine folks.

https://phillipsandtemro.com/solutio...block-heaters/
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Old 03-03-2020, 06:32 PM   #19
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Ok so where are these things and how can I find out if they are thermostatically controlled?
Look around the starter area of the block, I think most go over there in a core plug location. Once you find it (most use flat three conductor black cable), follow the cable and if you have a tstat the cable will go from heater to tstat and then to power source. Straight from heater to power source, no tstat.

You can also figure watts by watching the ammeter when you turn it on. Assuming 120V power, 10A is 1200W. If 240V, 5A is 1200W.
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Old 03-04-2020, 12:02 AM   #20
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Block heaters work better. They put the heat in the block and head, exactly where you need it for cold weather starting. My block heaters in my mains were there when I bought the boat 10 years ago and still working. I did have to replace the wiring.
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