Block Heaters

When we boat-sat for away customers, our instructions varied drastically from boat to boat.
One customer wanted his engines and gen set started and run just for 20 to 30 seconds, twice a month.
Never getting warm to draw condensation but just to clear the lungs and move some oil.
Another wanted them just bumped over. Others wanted us to run them under a load off the dock (my faves).
Others would seal up their exhaust with a fender or kids play ball and instruct us when to turn the block heaters on / off.
Still others left their engine rooms open to the interior and left the A/C systems running in away mode (de-humidifier) with fans running or a stand alone de-humidifier running with fans blowing into or around the E R..
All above stated that is the way it has been done for years with zero problems.
In the many years Josie's company did this this, the same customers kept returning for many years with zero engine problems.
Who knows what way is best.

Of course the cobbler's engines were never treated this well. Block heaters just before starting cold in the cold mornings is all they ever got.
When it kept freezing for a few days, turned on then. Helped keep the whole boat warm.

Our last boat had 3412's with 2 elements per engine. Not only did they draw a lot of current, one of the elements would burnout every winter if left on a lot. Once those bid chunks of iron warmed up the er was toasty. I think heating the er with a fan for circulation works good for all mechanicals and electrical. Of course if in the water, run the engines at least once a month. Block heaters or some form of heat would help lower the internal moisture, closing off the er vents makes a big difference. There was a thread awhile back mentioning heat pads that that could be adhered to the oil pan or block that worked well as a block heater.

I agree on not needing during winter layup. I typically turn mine on 4-6 hours before firing up my Detroit 671 TI's to lesson the smoking. I heard that some people leave their block heaters on all the time during boating season per this thread and others but a mechanic told me that you can fry them out if you leave them on all the time. Not sure who is correct? Maybe it depends on what kind of heaters you have? Not sure....

I have immersion heaters that I keep on all winter and the colds months of the spring and fall. In 21 years I have not had to change a heating element (looks much like a hot water heater coil). Only changed the thermostat plug end twice in that time. Costs a little in electric but keeps that engine room and equipment dry and warm. BTW, I store in the water

Just to understand, Beau: your boat is in the location of your profile, I suppose?
I keep mine in a place whose climate is more similar to FL (hurricanes aside, thanks God! ), and I never even thought to install block heaters for winter. But I can see why it can make sense in NY.

Yes. Describing my NY protocol. I wouldn't follow this protocol if in a Fl climate. My block heaters came factory installed by MAN.

Yup, sounds logical.
I'd be curious to hear if someone much further South is aware of factory installed heaters on MAN engines.
I suppose it depends on the first dealer who originally sold the boat, and its location.
In fact, I'm aware of their availability as an OEM part, but I've never seen them fitted in any boat here in the Med.

They are popular in the NE. I suspect most Posts, formerly a NE manufacturer, with MANS have them. Probably not a popular order item for boats cruising exclusively in the Med, just like Prop Shield is not a big item for NE boats

Its only my experience, but for 21 years I have never had a problem with the submersed portion of the heaters. The element material is pretty substantial and are located in the lower portion of the blocks. The thermostats are located in the heat exchangers. My engines are warmed entirely since all of the cooling water is heated to temp. What is a "toaster" heater?

Similar to the wire in a toaster, laundry and hair dryer. Installed in the air inlet path somewhere after the air filter, resistance wire that gets hot, warms up the air around it and helps a cold boat engine start easier.
Old Cats (396) and Cummins Bs commonly used them.

Pre-heat glow plug type concept. We had them on the old Cats and Onans.

I like the idea of the exterior oil pan heaters warming the metal and not the heater element immersed in the coolant There was an earlier thread covering the subject.

Just curious, why that preference? The oil pan warmers only heat the oil, correct? BTW, I believe my thermostats are 90 degrees off. Toastie. Also the MAN engine use grounds/hull zincs instead of engine zincs to abate electrolysis.

Based on earlier comments on another thread the oil pan heaters will warm the engine same as the heater elements immersed in the coolant. I had problems with the block heater elements burning out on Cat 3412's. Could have been air causing the problem? You could hear what sounded like boiling water when on, think they were 1200 watt elements, 2 on each engine. I would prefer the heat pads on the pan or block to heat the engine and gear. Actually my preference now is heating the whole er with a fan to circulate the air. Keeps everything warm and dry. Plus our er vents have hinged covers so when closed it makes heating the er easy. Nothing wrong with your block heaters, just had problems with the set up on our last boat. Our current Cat 3406 engines have block heaters installed but never wired to the panel. Also wonder if high heat on the coolant elements have any effect on the coolant over time. Being in a warmer climate is much simpler than boats up North. My concern is not below freezing temperatures, only condensation and cold starts. I think MAN's engine wiring eliminating zinc's is definitely the best. Had two boats in the past with MAN's.

My $.02 is that the heating pads that go on the bottom of the oil pans are inferior to elements that heat coolant. When your engine is sitting there, no oil is being circulated and most of it is just sitting in the pan. So the heat has to rise through air above the oil or via the sheet metal of the pan and into the engine block. And although coolant is not circulating, the heat still transfers reasonably well throughout the coolant and provides much better and more even heating. My new CAT's have a heat probe in the coolant and then a separate thermostat probe to maintain temperature without overheating and cooking things.

Actually IMHO the big problem starting a cold motor is the cold oil that gets sludge like and doesn't readily get pumped through the motor.

Although having the engine oil preheated to promote better flow and lubrication is certainly a plus, I don't see this as a main reason to pre-heat. Most of the pre-heat is to reduce or eliminate the smoke at start-up. It is my understanding this is accomplished by pre-heating the fuel and associated components, not the engine oil. But perhaps I'm confused on this?

The smoke is due to insufficient combustion. Is that due to the diesel being too thick or the motor operating inefficiently due to thick oil? I DK which will reduce the smoke faster. After having a motor almost grenade one cold January night I'd be more concerned with lubrication than smoke.

Some real (old?) engines have cast oil pans that will transfer heat to the block. I don't see a lot of heat transferred up from a tin oil pan.

Warm oil, heat may rise.
1/2 ton of cold cast iron above the warm oil.
I don't see a lot of comfort in this either.

Naw, I'm a water heater fan. Been working for me now 17 years.