A couple of different winterizing questions.

[vetplus40]

I wanted to ask a couple of questions regarding winterizing techniques/ theory and I will try and be brief. These questions relate to things that I have read regarding different winterizing techniques. My motor is a 5.0
1. If a motor is run on muffs until it reaches operating temp, and then the block is drained BEFORE adding AF, would it not be a bit dangerous to start a hot motor without having any coolant in it? I realize that the impeller will supply water quickly, but will it be soon enough to keep from potentially damaging the engine?

2. If you add AF to a running motor via muffs (as compared to simply filling the block) can residual AF seep into the cylinders when you shut the motor off? I realize the same condition would exist when operating and shutting the down on the water as well. I guess what I am asking is if exhaust pressure helps keep water out of the engine. I know it does with Jet skis, but I am not sure about Mercs. Thanks

 

[crazy charlie]

buy a Camco kit and follow directions.you can either pull the Tstat for the procedure OR run engine until warmed up and introduce Room temp AF combined with HOT water to assure Tstat stays open.Charlie

 

[Grub54891]

Drain the Block, manifolds, heat exchanger, and the circulating pump, Hook up the muffs to the anti freeze jug, start motor and let the impeller do its work. If the seawater pump is mounted on the motor, you will have to use a pump to make sure the anti freeze makes it to the seawater pump. On the other hand, if its fully drained properly, air don't freeze/crack blocks.

 

[Scott Danforth]

Or just chainge oil, then drain the block and exhaust and hoses. Then if you want to add AF, use a funnel

 

[muc]

I wanted to ask a couple of questions regarding winterizing techniques/ theory and I will try and be brief. These questions relate to things that I have read regarding different winterizing techniques. My motor is a 5.0
1. If a motor is run on muffs until it reaches operating temp, and then the block is drained BEFORE adding AF, would it not be a bit dangerous to start a hot motor without having any coolant in it? I realize that the impeller will supply water quickly, but will it be soon enough to keep from potentially damaging the engine?

2. If you add AF to a running motor via muffs (as compared to simply filling the block) can residual AF seep into the cylinders when you shut the motor off? I realize the same condition would exist when operating and shutting the down on the water as well. I guess what I am asking is if exhaust pressure helps keep water out of the engine. I know it does with Jet skis, but I am not sure about Mercs. Thanks

I've done a few thousand engines using this method. No problems.

 

[tpenfield]

1. If a motor is run on muffs until it reaches operating temp, and then the block is drained BEFORE adding AF, would it not be a bit dangerous to start a hot motor without having any coolant in it? I realize that the impeller will supply water quickly, but will it be soon enough to keep from potentially damaging the engine?

2. If you add AF to a running motor via muffs (as compared to simply filling the block) can residual AF seep into the cylinders when you shut the motor off? I realize the same condition would exist when operating and shutting the down on the water as well. I guess what I am asking is if exhaust pressure helps keep water out of the engine. I know it does with Jet skis, but I am not sure about Mercs. Thanks

1) The engine will not begin cooling itself until enough water is pumped into the block so that the recirculating pump can start moving water/AF through the block. Typically, this will be about 2-3 gallons of water, which may take about 30 seconds at idle speed. It is doubtful that 30 seconds will do much/any damage. . . IMO. What might be more damaging (to your hands) is draining the water from a hot engine.

2) Exhaust pressure does not keep water out of the engine. As you may know, water is introduced to the exhaust at the end of the elbow, which is oriented in a 'downhill' manner. When the engine is off, the pressure is atmospheric all around, so no back pressure to speak of. If your exhaust is working properly, then there is really no risk of water flowing 'uphill',

When an engine is idling the exhaust flow is more 'pulsating' than continuous, and a situation called 'reversion' can arise. Marine engines, having 'wet' exhaust systems, also need to have a 'mild' camshaft for operating the valves. In an automotive engine, the camshafts are designed to provide a small amount of valve 'overlap' meaning both intake and exhaust valves are open at the same time (for a brief moment) during the engine's revolution. Basically, before the exhaust valve has closed, the intake valve starts to open. With both valves (slightly) open at the same time, high pressure (exhaust) wants to move towards low pressure (intake) and so a slight reversal of flow can take place, until the exhaust valve fully closes.

In the situation of a marine engine, running at idle speeds, water could be pulled back down into the exhaust manifold during this reversal of flow ( i.e. reversion). That is why marine camshafts are designed with enough separation of valve opening and closing so that both valves are not open at the same time (overlap). More performing marine camshafts have a slight amount of overlap, but not enough to promote reversal of flow.

Short answer is no . . . not a concern.

 

[vetplus40]

1) The engine will not begin cooling itself until enough water is pumped into the block so that the recirculating pump can start moving water/AF through the block. Typically, this will be about 2-3 gallons of water, which may take about 30 seconds at idle speed. It is doubtful that 30 seconds will do much/any damage. . . IMO. What might be more damaging (to your hands) is draining the water from a hot engine.

2) Exhaust pressure does not keep water out of the engine. As you may know, water is introduced to the exhaust at the end of the elbow, which is oriented in a 'downhill' manner. When the engine is off, the pressure is atmospheric all around, so no back pressure to speak of. If your exhaust is working properly, then there is really no risk of water flowing 'uphill',

When an engine is idling the exhaust flow is more 'pulsating' than continuous, and a situation called 'reversion' can arise. Marine engines, having 'wet' exhaust systems, also need to have a 'mild' camshaft for operating the valves. In an automotive engine, the camshafts are designed to provide a small amount of valve 'overlap' meaning both intake and exhaust valves are open at the same time (for a brief moment) during the engine's revolution. Basically, before the exhaust valve has closed, the intake valve starts to open. With both valves (slightly) open at the same time, high pressure (exhaust) wants to move towards low pressure (intake) and so a slight reversal of flow can take place, until the exhaust valve fully closes.

In the situation of a marine engine, running at idle speeds, water could be pulled back down into the exhaust manifold during this reversal of flow ( i.e. reversion). That is why marine camshafts are designed with enough separation of valve opening and closing so that both valves are not open at the same time (overlap). More performing marine camshafts have a slight amount of overlap, but not enough to promote reversal of flow.

Short answer is no . . . not a concern.

Thanks for the detailed response. I assumed that some water could back flush when reducing power since my exhaust tips have a flapper in them, but I wasnt sure past that.
I used to do the adding AF with muffs, but it got to be a bit of a pain. I now just drain ( I have an easy drain knob) add AF through the large water pump hose. I do run a bit through the hoses going to the exhaust elbow until it trickles out the exhaust. The front of the exhaust elbow gasket does have a small hole in it and I wanted to make sure that when I run AF through the elbow, I wasnt inadvertently getting some in the block.
That said, I still don't think I am gutsy enough to start a hot motor with no water or AF in it.....lol