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Block Heaters

Discussion in 'Engines' started by 993RSR, Dec 9, 2020.

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  1. 993RSR

    993RSR Senior Member

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    I just received a newsletter from a VA Marina that mentioned block heaters are dangerous. My block heaters are on 24/7 when the temp goes below 60. The boat is hauled now fully winterized with the block heaters on.
    Anything I should know?
  2. MBevins

    MBevins Senior Member

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    Any particular reason you're running the heaters during winter lay-up. I fully understand while in the water , which I do as well.
    As per hazard, only thing might be a shorting situation, but quite frankly if properly protected that's not a probability.
  3. 993RSR

    993RSR Senior Member

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    I have a mental picture of the combustion chambers and valve/head assemblies rusting during the winter. I also cap off the exhaust. The block heaters were replaced this year.
  4. MBevins

    MBevins Senior Member

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    Is it inside heated? After asking, probably not as I don't know any indoor that allows boats to be plugged in.
  5. DOCKMASTER

    DOCKMASTER Senior Member

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

    Beau Senior Member

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    Is your vessel fueled by gasoline or diesel? Did the warning identify block heaters or space heaters, which are a notorious fire risk?
  7. 993RSR

    993RSR Senior Member

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    So I sent text messages to two engine surveyors and my Cat tech who winterized. They all replied basically the same:
    The benefit to leaving the block heaters on is it will eliminate moisture build up in the motor. To be effective over the winter while hauled you need to cap off the hull exhaust outlet and secure a plastic bag over the air cleaners.
  8. 993RSR

    993RSR Senior Member

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    My boat is diesel and the marina newsletter said block heaters. Gas engines do not have block heaters as far as i know
  9. DOCKMASTER

    DOCKMASTER Senior Member

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    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.
  10. Soulstice

    Soulstice Member

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    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.
  11. Beau

    Beau Senior Member

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    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.
    Last edited: Dec 9, 2020
  12. 993RSR

    993RSR Senior Member

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    We all rely on experts when questions like this come up. In SE FL we have a Cat specialist known as Tim the Cat Man. Tim highly recommended blocking off intake and exhaust air and leaving the block heaters on while the boat is hauled and winterized. Good enough for me!
  13. mapism

    mapism Senior Member

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    Does this Tim chap assume that all boats have block heaters?
    I wouldn't have expected them to be so popular, among FL boaters.
  14. 993RSR

    993RSR Senior Member

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    The benefit is substantially reduced if you never leave tropical waters. During past winters leaving the boat in SE Florida I would turn them on when the temps dropped into the low 50's or less then rose to the high 60's or more during the day. Reduce moisture.
    Block heaters are more necessary on boats that cruise the coast.
  15. NYCAP123

    NYCAP123 Senior Member

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    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.
  16. Prospective

    Prospective Senior Member

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    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.
  17. Beau

    Beau Senior Member

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    A
    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.
  18. NYCAP123

    NYCAP123 Senior Member

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    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.
  19. rtrafford

    rtrafford Senior Member

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

    bayoubud Senior Member

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    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.