Block Heaters

[Baker]

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?

 

[rslifkin]

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.

 

[PM]

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

 

[Baker]

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.

 

[rslifkin]

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.

 

[Sailor of Fortune]

Id leave them on for corrosion reduction. Either your built in ones of Tonys' Wolverine pad heaters.

 

[O C Diver]

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.

Ted

 

[Ken E.]

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.

 

[firehoser75]

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.

 

[caltexflanc]

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.

 

[Ski in NC]

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.

 

[Baker]

Ok so where are these things and how can I find out if they are thermostatically controlled?

 

[FF]

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.

 

[psneeld]

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.

 

[rslifkin]

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.

 

[psneeld]

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.

 

[firehoser75]

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.

 

[caltexflanc]

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/soluti...ctric-immersion-heaters/engine-block-heaters/

 

[Ski in NC]

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.

 

[Lepke]

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.

 

[catalinajack]

In eighteen years of ownership of a Chevy Duramax, I have used the block heater only once. That was in northern Vermont visiting the in-laws with an overnight temp of 15 below zero. Many other times there I have started the engine unheated down to zero degrees. Every time, the engine started straightaway but it clattered and moaned and groaned for a minute or so. Synthetic oil helps immensly in those conditions. The engine spins freely even at 15 below.

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.

Ted

 

[catalinajack]

Followup on my comment on my truck diesel. I did not intend to suggest that block heaters are not effective as described by others. In my case, the Duramax starts easily in very cold temps. Many boat engines do not but my Lehman 120s start easily in engine room temps down to 45 degrees. I have never experienced temps below that attempting startup. The lowest in-water temp I have seen in my engine room was 35 degrees after a several day spell of single-digit overnight temps.

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.

 

[FF]

"There may be other benefits beyond "go now".."

The ability to take a heavy load instantly.

The big cruise ships use pod drives and have massive house loads , depending on time of day.

There generators feed their coolant to an unused generator , so on starting it is ready to accept a load.

 

[jleonard]

I had a block heater on the 6BTA I repowered my old Mainship with. It was nice in the spring and fall as it kept the floor warm.
It was thermostatically controlled and I believe it was at 120 F. That was actually too hot to have the engine when doing an oil change, etc.
The engine did NOT need that or the grid heaters to start easily during a new England boating season.
I also had a block heater on the Cummins 6BT that was in a pickup truck. It sat outside 24/7 and in the winter I used a timer to start the heater about an hour before I left for work. That made starting easier as the grid heater would think it was above 55F and not come on. It was also just warm enough to put out defroster heat immediately for those days of freezing rain or snow.

 

[Baker]

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.

Thanks Ski...that's the info I was looking for. And I do think I have seen them. These engines are 14 years old and look brand new....probably a reason for that!!!

I also read somewhere that many installations alternate between engines as to not have a ton of electrical load all at once. Does that sound familiar? 2400 watts would be a a pretty big load.

 

[FF]

"2400 watts would be a a pretty big load."


Especially if the power post is metered.

 

[O C Diver]

In eighteen years of ownership of a Chevy Duramax, I have used the block heater only once. That was in northern Vermont visiting the in-laws with an overnight temp of 15 below zero. Many other times there I have started the engine unheated down to zero degrees. Every time, the engine started straightaway but it clattered and moaned and groaned for a minute or so. Synthetic oil helps immensly in those conditions. The engine spins freely even at 15 below.

My Dodge will start well below freezing without the block heater. I focus on "Best Practices " for longevity. With 489,000 miles on the engine now, I'll keep doing what I'm doing.

Ted

 

[ASLIII]

My old Detroit Diesels will not start after 24 hours of shutdown unless Pre-heated. Was used to this ritual since my airplane requires pre- heating. Ultimately, I guess it depends on your engines, but warm oil and diesel fuel seem to make sense.

 

[catalinajack]

Every engine is different. Today we went out for a few hours. Engines have not been started since last Fall. Block temps were 57 degrees. Lehman 120s fired off almost immediately. We are just south of Annapolis, MD for reference.

 

[tozz]

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.

This is exactly why I leave mine on for my DDs here in Seattle. Reduces smoke at startup and controls temp/condensation down in the engine room.