Block Heaters

Curious why you leave block heaters on during lay-up regardless of in water or not?

Is your vessel fueled by gasoline or diesel? Did the warning identify block heaters or space heaters, which are a notorious fire risk?

Lots of debates on the benefits of this vs cost and there will never be consensus. Curious, if the air filter is bagged and exhaust is plugged, how does the heated moisture escape the engine? My engine manuals are silent on running heaters while laid up and my CAT dealer said there is no need.

I turned mine off for a week last December when I was servicing my cooling system and the entire engine room was soaking wet the week it was off from condensation. Once they were back on, the engine room stays warm and dry no matter what. I leave mine on almost the entire year to prevent condensation on/in the engine.

Agreed, It would have been concerning if you had answered that it was gasoline. The reason that I asked about the space heater is that marinas annually have to fight the battle of some folks insisting on having them. Space heater not block heater in my experience are usually the target of those warning, I suppose some space heaters are less a problem than others, but I wouldn't know that.

I also keep my block heaters on in the colder weather and when winterized for the very reason you state. Plus it adds a couple of degrees to the salon above and keeps the engine room warm and dry of condensation. I have a lot of equipment in there which I think benefits from the warmth and dryness also. I also have a small fan that helps circulation. In addition to closing the exhaust and bagging my airseps, I make sure I have closed off my hull air intakes too.

This is a new one on me. Of course we left the block heaters on with boats that ran through the winter, but I've never seen it with boats that were laid up. In fact I find it hard to imagine all the boats in a storage yard being plugged into electric. Do these yards add an electric fee to your storage rate? I can't see it being bad for the motors except for the fire possibility, but just odd. We do of course recommend plugging the exhaust, but that's to keep critters out, and we also put Damp Rids everywhere. As far as covering the air seps is concerned it seems to me that any moisture in the air not sucked in by the Damp Rids will be stopped at the filter since the motors aren't sucking the air in. Also, at least up north winter air is pretty dry. Down south that's a different story, but who lays up for the winter down south? Like I said before I don't see any harm from doing it. It just seems like wearing a belt and suspenders.

Definitely not the norm here in the North East. No yard I'm familiar with will let you leave anything plugged in while you're away from the boat anyway. I will agree that when I go in the engine room in the winter it can be pretty damp. I can't attest to if this is a problem or not, just that it's pretty normal and I don't feel like engines are randomly grenading due to moisture up here. I guess, If I could leave block heater on and keep the engine room warmish and dry I'd probably due it. But since I can't and pretty much nobody else up here can, I'm not too worried.

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Agreed, I've not seen it on boats stored on the hard, but is quite common for boats stored in the water. Keeping your engine heaters on is almost universal for folks in the water.

Put Damp Rid in your engine room and it'll collect the dampness. Yes for boats left in the water not only keep the block heaters on but start your motors at least monthly to keep them lubricated. You're there anyway to check on the bubblers and to make sure all is OK so it's no extra hassle.

Agreed, although several I know transitioned to diesel furnaces focused on keeping ER temps up, overall, and not using the block heaters.

Tim explained to me that the exhaust and intake is like a air pump. As the air temp and pressure changes daily it will move small amounts of moist air to the cylinders thru the open valves. The very reason you here of pitted valves and seats, on boats that sit too long between operating. If in the water you can run the engines at the dock monthly as recommended by many on this forum. Because I can easily check my boat daily using a heater that circulates air in the er to control condensation keeps everything warm and dry.