Continuous use of block heaters

I manage yachts in South Florida and never leave the block heaters on. They chew through a lot of electricity. But, I generally start and run the engines on every yacht, every 2 weeks and don't have any issues with corrosion inside the motor (verified with oil samples). I'd rather run them every 2 weeks. Block heaters IMO may create other issues by drying out the saltwater in the raw water side of the engine and concentrating it as saltier and saltier, if the yacht just sits 30/60 days on block heaters without running.

I just had samples pulled on a new set of 1200HP MAN's with 80 hours on the intial oil. We took delivery of the vessel beginning of August 2019, but vessel did it's sea trial at the factory in April 2019 where it then sat, then sat again while it was on the deck of a ship for almost a month. Iron is 10/14 PPM, Copper is 25/29 PPM, Aluminum 4/4 PPM (port/STBD) . All other metals didn't even register. That's a pretty **** good oil sample for the break in oil of a new engine after 80 hours of use, at least half to 2/3 of it at 80% load.

Have been using an inexpensive ceramic space heater with two settings, fan, and tip over switch in the winter. Controls the humidity in the ER, and uses less electricity. Running engines often keeps the internals dry as Capt J recommends.

I've never used block heaters, it's a lot of BS, and I boat ( run the boat) April through first week of December here in Cape May / Upper Chesapeake bay. That's been on my 6V53s and 471 TIs . If it gets in the lower 40s I will run a ceramic heater , while I'm on board , to the ease the start in the morning for a trip. But she will fire up regardless.

I would never run any type of heaters in the bilge / engine room. In fears of a short and fire. You are asking for trouble . Condensation in the engine? Lol, we all have plenty of other things to worry about on a boat/yacht engine condensation would be my very last worry. What Capt J recommends, run them every two weeks and you will be fine . Plus you are in Florida!!

After I pickle my engines for the winter ( I run anti freeze thru them rather than draining) I turn on at least one engine heater (submersion type) from late Dec to late March. Gives the engine room and salon above a little warmth. Been doing it for 20 years without evident damage. During the season I run the engine just about weekly so I don't really have the need for heaters then.

I like a dry ER, eliminates some electrical problems and don't like wet engines, our bilge stays dry too. The ceramics also circulate the air. Nothing wrong with block heaters except they draw a lot of amps and past experience went thru some elements. Not all of FL is warm in the winter, the northern gulf can get cold and damp!

What ! Florida in general is warm! Lol... Try living aboard in Phila., one winter I was frozen in solid all of February, never rocked from passing tug/ ship traffic all 28 days.....But I did have the heat on through out most of the boat and a 100 watt light bulb in a clamp on work light, and one aimed at the number one bilge pump! Lol.
To each is own, I like simple 75/100 watt light bulbs they dry the air, which I agree is nice, and keep things just above freezing kind of and are a low draw on the Amps.

cleanslate, I never thought of the positives of being aboard when the water is frozen, no wakes! lol True, with the light bulbs, nothing mechanical. KISS!

Ice plays havoc with a painted waterline, that for sure. No bubblers in Baltimore?

I have 250w Wolverine oil pan heaters on my antique 8v53's. They run 24/7/365. In Winter I have covers with gaskets that snap on over the hull vents to keep the wind out. Engineroom stays at 40 degrees even on the coldest days. Always easy start ups.

How long do they last running 24/7/363?

Phila, .. Had two Kasco de - icers on the transom area , kept it clear by a foot or so. My exhausts are an inch or so above the water when 1/2 full on fuel. So no water in pipes . My aft sink drain would freeze shut at times, from bottled water being poured down the drain which runs aft out the transom under swim platform . That was on the real cold days , 20s and under .

Do you live aboard 12 momths - I am SOOO envious, I think?

No more, I did a three year stint 2014 through 2017. Now I'm just a weekender. It was a great time living aboard, but it was also nice to get on dry land. Sometimes the rocking all night and sometimes day long was a pain.
The marina I was at was not well protected on a North East blow.

I'd have to look in my file but I think they have been in there for 8 years or so.

They have held up well for continuous service.

Not sure I'd use them 24/7, a low wattage heat bulb may do the trick to keep the engine room dry. I do know that I use engine heat on my coach diesel anytime it's 50º or under and it starts a LOT smoother, almost no glowing and immediate oil pressure and smooth idle.