Unclamp bypass when winterizing?

[Bratina]

Just hauled out here on Lake Ontario, and did my normal ritual of prepping a bucket to draw antifreeze, removing the thermostat and clamping off the bypass hose to force the antifreeze through the block. I ran the engine until the exhaust water was pink, un-clamped the bypass, fogged the cylinders and put the engine to bed.

On the drive home I couldn't decide / remember if in prior years I've run the engine briefly without the bypass clamped as well. In the end I went back to the boat and, still without the thermostat in, ran the engine for a short while without the bypass clamped.

My question is whether I needed to also run the engine without the bypass clamped? In the end it didn't take long since I still had the hose to draw the antifreeze installed, but it would be good to understand if I needed to.

[tenders]

The bypass needs to be clamped even when the thermostat has been removed. EDIT: or are you asking if you need to run it unclamped after you’ve run it clamped? I would say it doesn’t matter.

From the water pump, without the thermostat, there are two paths to the exhaust.

Path 1: through the bypass, through the external passage of the thermostat housing, and out the exhaust. Pretty straight shot.

Path 2: angled through the bypass, through the engine cooling passages in the block and the head, through the internal passage of the thermostat housing, and out the exhaust. A fairly tortuous path.

If the bypass is not clamped, the water/coolant will almost certainly choose the low-resistance Path 1 and not go through the block. In avoiding the block, of course, all the raw water in the block remains and will freeze.

Clamping the bypass prevents that straight shot and forces the coolant through the block, displacing and diluting the raw water with antifreeze.

I avoid all this complexity by having no thermostat at all, and a bolt stuffed into the hose past the bypass, essentially clamping it off. This forces nearly all the raw water through Path 2, all day, every day, all summer, and all winter. For winterizing all I need to do is suck a gallon or two of antifreeze through the raw water intake, never worrying about whether the engine is warmed up, the position or condition of the thermostat, or the completeness of the bypass clamp. Yes, the engine runs cold, and has since 1993.

[Bratina]

The bypass needs to be clamped even when the thermostat has been removed. EDIT: or are you asking if you need to run it unclamped after you’ve run it clamped? I would say it doesn’t matter.

Thank you Tenders: I was asking if I needed to run it unclamped after I already ran it clamped, as I was concerned about some water left behind if I didn't.

I suppose it's easy enough to add a few seconds 'unclamped' to my winterizing routine if it was needed, but it sounds as though it's not.

[sastanley]

The bypass is about 12" of 1/2" hose...there will be plenty of pink stuff mixed in that area with it clamped. The objective is to fill the block with antifreeze (and the manifold and exhaust system too)..

You did no harm running it with the bypass open for a short period since you clamped it first and hopefully filled the block, but, just wasted a little pink stuff out the back while running with the bypass open.

If you had left the bypass open (unclamped) during the entire antifreeze sucking phase, most of the antifreeze will skip the block and run thru the easier bypass path and then to the manifold and out the exhaust until the t-stat opened (if it is in place.) This wastes a LOT of antifreeze. (This is the undesirable scenario)

[Bratina]

The bypass is about 12" of 1/2" hose...there will be plenty of pink stuff mixed in that area with it clamped. The objective is to fill the block with antifreeze (and the manifold and exhaust system too)..

You did no harm running it with the bypass open for a short period since you clamped it first and hopefully filled the block, but, just wasted a little pink stuff out the back while running with the bypass open.

If you had left the bypass open (unclamped) during the entire antifreeze sucking phase, most of the antifreeze will skip the block and run thru the easier bypass path and then to the manifold and out the exhaust until the t-stat opened (if it is in place.) This wastes a LOT of antifreeze. (This is the undesirable scenario)

Thank you, that makes sense, and it's good to know that other than wasting a little pink stuff, no engines were harmed during the winterizing of the boat when I re-ran with the bypass open for a little while.

I run a lot of a/f through the engine - more than I need most likely, but antifreeze is relatively cheap(ish), and I sleep easier when it's cold this way.

[sastanley]

I think you're safe!

Sorry your boat is put away for the season though..I am hoping to do some fall cruising this weekend!!! (if the weather is not totally miserable.)

[Jim Booth]

With T-stat?

I didn't used to have a T-stat and winterized while still in the lake after running a half mile or so to the crane. I also had the bypass pinched off. This season I put it back to original with an expensive T-stat and removed the clamp. Now I'm sitting in the boat on its trailer and confused. Do I have to remove the T-stat first, and clamp off the bypass, then suck pink for a while, then unclamp the bypass to suck more with the T-stat still removed?

I'm running an electric space heater and it's not supposed to be a hard freeze tonight, but it would be nice to do it tonight.

Jim

PS. Is there any way to avoid removing the T-stat now?

[Peter]

Jim,

I believe you should remove the t-stat unless you are able to bring the engine fully up to temperature such that the thermostat opens. Then and only then will any coolant circulate through the block. If you try to winterize with the thermostat in and not warmed up, the thermostat will prevent the anti-freeze from flushing the block and simply let it all through the by-pass.

As noted in the manual - "In engines with raw water cooling, I always felt it necessary to remove the thermostat prior to step 3 (the anti-freeze flush) and to temporarily squeeze off the bypass hose to the thermostat housing. This precaution ensures that the anti-freeze has to flow through the block."

You do need to attempt to flush both the block and the by-pass once you have removed the t-stat. My strategy is to open the by-pass, start the engine and then close the bypass for the rest of the anti-freeze flush. The initial few seconds with the by-pass open is enough to flush the by-pass.

I do it in that order simply because doing it in reverse order would require me to accurately estimate when the anti-freeze will all be sucked in order to open the by-pass a few seconds before that and then dash up to stop the engine.

It is possible I have an excessive fear of running the water pump with no fluid running through it...

As noted above, having a little water left in the by-pass is probably not a big deal. Flushing the block is priority #1.

Hope that helps,

Peter