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-   -   Block heater (http://www.wakeworld.com/forum/showthread.php?t=795809)

kevin 10-04-2012 11:06 PM

Block heater
Has anyone used a block heater on their boat to extend their riding season when it's just getting to freezing at night. I know the heater would still need to be drained, but has anyone done this? Just curious.

boardman74 10-05-2012 5:27 AM

I don't think it would work. Those things get red hot and will actually boil the coolant around them. If they heat up dry they will shatter/burst. So the problem I see is that with an open cooling system the water drains down out of the engine some. Plus as the water heats it naturally starts to move as the warmer water rises. That could push more water out of the cooling system. I would be concerned with the element getting dry. I think one of the magnetic oil pan heaters might work better.

Disclaimer: I am a diesel mechanic and this is just a theory. But I can tell you if they run dry it's not good having seen it.

polarbill 10-05-2012 8:09 AM

I wonder if a magnetic block heater or 2 would keep the engine compartment warm enough to keep it from freezing? One or 2 of them may keep the engine and tranny warm enough that you wouldn't have to drain the water but the heater is another story. You could drain the heater lines and bypass it all together so you don't have to drain the heater but then you lose the use of a heater which would be really nice if it is cold. Rather than do that the slick setup might be to add quick drain petcocks to all the spots than would need to be drained. Most older boats just had a drain on each side of the block, a drain on each exhaust manifold/riser and one on the bottom of the tranny cooler/exchanger. You would still have to pop the heater line(s) off and blow those out and may or may not want to drain the water hose on the engine but I would think this would be a 5-10 minute job draning the water and it would be ready to fire right up when you wanted to use it.

I think I have actually seen a setup someone made that had one handle you turn and all the water drains out. That would be pretty slick for those that want to use their boat year round where it freezes occassionally.

Iceberg 10-05-2012 8:13 PM

For a closed system it really doesn't matter, except for the fresh water side. The closed system should already have anti-freeze in it. You don't need a block heater until 0F. I doubt you would be out with water below 50F. For the fresh water side, an in-line heater with a pump would be the only way to go. A raw water system would need special plumbing to keep water out of the exhaust when not running.

If it is only a few degrees that you need, a 100w heater (light bulb) in the engine bay would work fine. I have done it many times trying to get a few more weeks on the water with out winterizing. We used one of these in a small pump enclosure. It was good to about -20F with no worries. Now the new boat I have has 30 ft of heater hose and an exchanger that is not easily protected. My only safe option was to put the boat in my garage. It literally fit with 3 inches to spare! Last weekend was 84F. Yesterday and today we got about 8 inches of snow with 50 mph winds! The ice on the hydro lines was about thick as a baseball bat in some areas.

antoddio 10-05-2012 8:46 PM


Try that. I have one. Never used it other than to try it out in the house. It puts out a pretty good amount of heat. Spec'ed for marine use as well. Leave it on the floor, leave the vdrive access open and it will warm the whole boat.

kevin 10-05-2012 9:08 PM

Thanks for the input. I would be interested in knowing the setup people have used to drain all the water with just a couple valves. If anyone has done this or knows what it would take please post.

boardman74 10-06-2012 7:54 AM

My mercruiser magnum has 4 plastic plugs and 2 brass plugs on the sides of the block....can drain it in right around a minute. So there is a brass plug on each side of the block, 2 plastic plugs on the bottom of the manifolds, and 2 plastic plugs on each side of the lower lines(cooler, etc) I have pulled the lines after doing that just to see whats left and there wasn't much anywhere. Thats a 97 not sure if all the newer engines are set up the same.

10-06-2012 9:17 AM

Honestly if its warm during the day and just touches freezing at night for just a couple hours, you'd be fine not doing anything. It takes a hard freeze for a couple days before it will actually do any damage to your engine. Having said that, I still wouldn't take any chances. I would just put a marine heater in the engine compartment over the course of the night if it was me.

rmcronin 10-06-2012 4:24 PM

Leave a shop light with an incandescent bulb in your engine compartment, put it on a timer. Will be like an ez bake oven. Draining your block, manifolds and hoses can also be done in under 5 minutes.

ndh2o 10-08-2012 5:43 AM


Originally Posted by polarbill (Post 1787922)
I wonder if a magnetic block heater or 2 would keep the engine compartment warm enough to keep it from freezing?

I have used this setup for MANY years with no problems at all. I have 2 magnetic block heaters connected to a thermo-outlet that comes on when it hits 35* and turns back off when up to 45*. The boat is garaged, and I am in Eastern NC where the temps only get so cold.

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