Block Heaters

I'm interested in hearing from those who use block heaters and the benefits you've experienced. I have land based emergency generators (500-2,000 KW)that utilize them but they go from dormant to 1800 rpm in less than ten seconds with monthly test runs. I live in an environment that ambient temperature often keeps these units above the 90 degree F factory setting but the factory maintenance techs insist on keeping them on anyway for piece of mind.

Am also interested in hearing from those that do not use them for a specific reason. I've often intuitively thought they made great sense on boats but may be missing something obvious.

I'm an ex-power plant and submarine engineer, in those apps machine heaters were commonly used. The point was to keep all metallic surfaces above dewpoint so condensation did not ever occur. It was not necessary to heat them way up like you would for starting in arctic conditions, just warm them up enough to keep them dry when weather caused temp and humidity swings. Probably 10F above ambient will do the trick.

Many block heaters are some serious watts for the arctic, unnecessary for condensation control. Probably 250w is enough for a six liter engine. Arctic heaters burn up lots of power ($$$) and also can burn up shore connections.

An engine kept dry will not corrode, at least on the surface. It is a good thing to do.

They keep them on because it is part of NFPA 110, section 5.3 Energy Converters - Temperature Maintenance. PS: They added battery temperature in the latest edition. I got hit on that one by insurers at one of my previous companies.

Anyways, I can't see a significant benefit in your situation.

If and when I heat my diesels I use both pan heater and circulation heater. Not enough, or uneven, heat just increases the likelihood of condensation.

Whatever you do ensure the temperature remains above the dew point so your engine internals will stay shiny.

D'oh! Ski beat me.

The single hardest thing on an engine is a cold start. No circulating oil coating the surfaces and cold oil to boot. Keep up the oil heater then add a pressure system to pump oil through the system before you hit the starter. 250 watts 24-7 I could not live with but a few hours b4 getting under weigh then OK. Thing is, we have our leisure boat engines being rebuilt waaaaay b4 they should be, sitting and no use is the killer. Btw, 250 watts is OK at the dock, on the cord, not on the hook..

I had 300 watt magnetic pan heaters for my 3208 Cats....when the engine room was 32 degrees...even with them on all night the block and coolant remained at 32 degrees...

Maybe they could maintain a temp...or a smaller engine...but they couldn't beat the heat loss on those engines.

I was hoping for a 10-20 degree rise...nope...nada...

Pan heaters don't get the heat up to the engine block very well. Probably ok for condensation control, but a heater in the water jacket is the gold standard.

Ski in NC said:

Pan heaters don't get the heat up to the engine block very well. Probably ok for condensation control, but a heater in the water jacket is the gold standard.

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I know that now...the advertising on those baby's was WAY off....

The block heater in my diesel truck showed me the real diff...and you are right about the wattages used as power hogs....

Also had a decent in line coolant hose one for my other truck...it was an inline 6 gasser I took to Kodiak, Ak...that worked OK but then again Kodiak doesn't get that cold usually....and it was much more than 300 watts.

always wondered how good/safe the dipstick heaters are.

My boat's Detroit 8v92's came with 1000w immersion heaters and 100 degree thermostats courtesy of a PO and they are really wonderful. When we stopped cruising full time and settled in North Carolina, I had them on 24/7 8 months a year, other than when running or after a run, or whenever it gets below 50. They keep the blocks an even temperature, in the winter I'd open the engine room doors and they would keep the lower level of the boat dry and warm all by themselves. Fast, almost smoke free starts. I liked the benefits so much I put a Wolverine (great company BTW) oil pan pad heater on the genset, which is in a separate room. As far as getting the warm oil circulating, on the Detroits, hold the stop and start buttons down several revolutions then release the stop.

I have had two diesel pickups and one tractor with diesel engines. The tractor has an air supply heater to use when it is cold out which works very well. Never had a problem starting the engine when the temperature was in the 20s or 30s.

The trucks have had block heaters and I have used them when the temps were in the 30s. The heater on the Ford 7.3 engine takes three hours to warm up the block at 1500 watts per hour. That is 50 cents a day so if I have to use the block heater for 20 days a month that is $10.

The block heater makes a big difference. The engine will start up easily and not vibrate at all. If the engine is cold, well it will start right up, but the engine is most unhappy.

Now I put synthetics oils in the truck and tractor, either Shell 5Wx40 or JD 0Wx40 and I don't have to use the block heater. Another advantage with the block heater is that you can have heat in the cab very quickly. No such luck when using a synthetic oil.

If I had a boat that had to start often in cold weather I would use a synthetic and not bother with the block heater.

Later,
Dan

I've been in SE AK for 7 years (been back to WA 2 years) and never had a problem cranking and starting my engine. I use 30 weight oil always.

I do put small low watt heaters in the engine compartment that are designed to reduce humidity. But they supply 100wats of heat. And also a thermostatically controlled 750w fan equipped electric heater. It's set low just to keep the engine compartment 40 degrees. It comes on occasionally to accomplish this or quite often when it's cold.

Never even thought of a block heater or oil heater.

Northern Spy said:

D'oh! Ski beat me.

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+1

Greetings,

Here in Ketchkan the winter weather would be considered mild by other parts of the Nation. Our winter months hover around 35 degrees.

Our engine space comprises the full run of the boat under the floor.

I have used one of those moister removal heaters in the past. This year I am going to try something different. We use “Easyheat” thermostat control devices on our home water pipe heat tapes. These come on at 38 degrees and cut off at 50 degrees. The thinking is to plug our external 110 engine pre-heating unit up to this plug. As the engine space becomes warm by the block heating up the controller will kick off and then as the engine space becomes cool, kick in again. These units look like this:

Amazon.com: Easy Heat EH-38 Freeze Thermostatically Controlled Valve and Pipe Heating System: Patio, Lawn & Garden

Regards,
Al

I bought a 250 watt magnetic heater and stuck it to the oil pan. I couldn't see where it made a bit of difference.

It doesn't get that cold in my area and the boat is heated in the winter anyway. I'm thinking something to heat the air would do better for humidity control.

If your boat is in the water, the engine will not get colder than what you are sitting in. As long as you have the correct viscosity oil, you are only looking at about a 20 degree difference between room temp and freezing in any case.

If you are fussed about cold starts, hold the fuel shutoff and crank until you have oil pressure.

Sitting on the ground the engines will get colder but you will not be starting them then, will you?

IMHO, unless you have a specific reason, block heaters are a waste of time, money and energy in a boat, very useful for engines in ambient air like trucks.

Using immersion heaters of the right power, the blocks themselves make great radiant heaters. As already mentioned, I'd open the ER doors in the winter and keep the entire lower level warm and dry. We'd seal and stuff the ER vents when the boat was idle.

It is apparent here that many people misunderstand the use for block heaters on boats, equating it with the use on land in bitter conditions. Fast and beautiful cold starts is only part of the equation. Cutting condensation within and around the engine is probably more important. Some accomplish the "around" part of that with light bulbs or other external heating devices. Sitting unused in a cool, moist environment ages diesels as does cold starting.

Keeping the metals a warm, consistent temperature between starts, rather than going from something 40, 50 degrees colder to operating temp will prolong life and reliability.

Look, if you really don't care that much about your equipment, don't use them.

If the boat was in Florida or other warm climate year around, I wouldn't go out of my way to install them either.

Thanks for the informative replies gang.

Xsbank said:

If you are fussed about cold starts, hold the fuel shutoff and crank until you have oil pressure.

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No cold start issues in my area of California but was interested in learning the other benefits to block heaters. The CAT factory tech was adamant about their benefit besides the NFPA requirements I have to adhere to mentioned by Northern Spy above. Really was interested in how it applied in a practical matter to boats specifically.

caltexflanc said:

If the boat was in Florida or other warm climate year around, I wouldn't go
out of my way to install them either.

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I have no plan on going out of my way to install one but if one comes my way it sounds like cheap insurance and multipurpose too

manyboats said:

Never even thought of a block heater or oil heater.

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Me either until I signed the invoice to have one replaced on a 1,000 Kw CAT generator the other day. Have heard many folks post about a variety of heating schemes on their boats to combat moisture issues since joining the forum. Block heater idea seemed to make the most sense to me and kills the most birds with a single stone. Not as important to the larger boats, but for those of us boating below the 30 foot scale need to get the most benefit for the smallest footprint on our vessels.

The biggest concern with moisture is in the mid and northern lattitudes where you get cold and warm fronts. Get a few days of cold weather, and engine cools down. Then a warm front comes through with warm air plus higher humidity. The engine will sweat like a cold beer. In mid summer, in Fla, in the dry parts of the pac coast, probably not an issue. Here in NC in fall, winter and spring we get these weather systems routinely.

I don't have a block heater on my engine, but if I know we are getting a warm front I go start the engine and gennie for a bit to warm them up.

Thanks Ski, our current boat will one day be situated on a triple axel trailer to be towed and staged at various points around North America. All of our modifications have potential overwinter stays in northern climates in mind. Heated indoor storage would be our preference if the boat does not move back south some years, but we all know sometimes stuff happens. Best time to prepare is before it becomes a need.

caltexflanc said:

If the boat was in Florida or other warm climate year around, I wouldn't go out of my way to install them either.

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Interestingly enough George most mechanics still recommend them even down here. We do after all get very humid days with sometimes broad temperature swings.

And +1 to all the rest.

Heat!

My previous boat had 1982 VolvoTAMD40A’s that were hard to start in the winter. My mechanic recommended oil pan heaters. We don't boat much after the last home football game with exception of a winter cruse to look at the occasional snow. After the install they would start easily with little smoke all winter.

Ski in NC said:

I'm an ex-power plant and submarine engineer, in those apps machine heaters were commonly used. The point was to keep all metallic surfaces above dewpoint so condensation did not ever occur. It was not necessary to heat them way up like you would for starting in arctic conditions, just warm them up enough to keep them dry when weather caused temp and humidity swings. Probably 10F above ambient will do the trick.

Many block heaters are some serious watts for the arctic, unnecessary for condensation control. Probably 250w is enough for a six liter engine. Arctic heaters burn up lots of power ($$$) and also can burn up shore connections.

An engine kept dry will not corrode, at least on the surface. It is a good thing to do.

Click to expand...

My main interest is keeping the iron dry as well rather than warm start ups. As you know, the worst moisture problems are usually in the winter when a sudden warm front comes thru. Cold iron and warm air=moisture on and in the iron.

My boat's Detroit 12v71TA's are equipped with one Hotstart SB model thermosiphon type heater per engine. After finding the model number (and observing their effect on my integral amp panel when on) turns out they are 2,250 watts each !

This seems like simply too much dock power drain to keep them on 24/7... but I wonder if their integral thermostats (100 to 120 degree range) will shut off the power enough that once up to aprox 110 degrees the total power usage will not be too bad per month ?

(which of course depends on how cold the weather gets as well but here in southern coastal SC it rarely gets below freezing)

Would a more cost effective alternative for iron dew point control be simply a small ceramic heater in the engine room plugged into a proper (i.e. accurate and reliable) remote thermostat ?



Hotstart SB tank type engine heater

I use stick on the oil pan 75 watt wolverine heaters that seem to do a great job in our high humidity environment of Alaska

ksanders said:

I use stick on the oil pan 75 watt wolverine heaters that seem to do a great job in our high humidity environment of Alaska

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Well, that brings up another controversy. And that is, seems like an oil pan heater might not warm the block as evenly as the thermosiphon type heaters that via water density decreasing, circulate warm water thru out the block. (assuming you have a fresh water cooled engine of course)

In other words, might the thermosiphon type heater inhibit what is dreaded most of all (and what you can't really tell from looking at the outside of the engine is happening or not)...moisture in the cylinders...better than an oil pan heater ?

Caladan said:

Well, that brings up another controversy. And that is, seems like an oil pan heater might not warm the block as evenly as the thermosiphon type heaters that via water density decreasing, circulate warm water thru out the block. (assuming you have a fresh water cooled engine of course)

In other words, might the thermosiphon type heater inhibit what is dreaded most of all (and what you can't really tell from looking at the outside of the engine is happening or not)...moisture in the cylinders...better than an oil pan heater ?

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Yes, I think a coolant heater would be better.

The oil pan heaters are nice, and are easy to install, and work pretty well though. How well I have no clue.

We use coolant heaters on our generators and vehicles in Alaska.

The engine will sweat like a cold beer.

It is sweating INSIDE too.(any cylinder with a valve open) .

Engines don't die from cold stats , they die from lack of use.

A good hard run (Not a dockside idle )every month will scrape the rust off the cylinders enough so the cylinder walls do not pit.

When rust pitted compression goes down and oil consumption goes up.

FF said:

A good hard run (Not a dockside idle )every month will scrape the rust off the cylinders enough so the cylinder walls do not pit.

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It seems to me that a few minutes of idling at the dock per week, combined with a heater to combat the dew point issue would help nearly as much as a "good hard run".

Having said that, I do wonder how long a protective oil film would remain on the cylinder walls after a dock idle run. Wonder if anyone has done borescope checks to find out ?

The mechanism, "sweating" is caused by 3 factors, RH of the air, the temperature of the air & the temperature of the component the air comes into contact with.
if the engine component is warmer than ambient how can condensation occur ???? even with 100% rh if the component is hotter than the air there will not be condensation.
if the component is warmed by an oil pan heater or a block heater makes no difference, it is temperature difference that drives the mechanism.
of course the heat input to the engine needs to be more than the heat lost by radiation for the engine to warm up and with low power sump heaters you probably will not feel the block warming...but if heat is applied to the bottom it must rise through the sump and the engine thus the internals must be warmer than the outside .... even if the outside of the block is still at ambient.
in any case can low temp winter air ever give rise to sweating issues??? surely as soon as it heats up (as it enters the house or the boat) air becomes very dry...certainly thats the case here

If engine temp is below dewpoint temp, it sweats. Simple as that. And yes, oil pan heaters may not feel like they raised engine temp, but probably do raise temp of some of the internals, a good thing.

Those with those high wattage heaters, one option is to wire both in series so they run at half voltage. Watts are then 1/4. Makes it easier on power bill and easier on shore cord.

For the boats that draw huge power , it is sometimes nice to have that 1500W immersion heater (or 2) on its own long power cord .

Especially if the next power pole is empty.