Trying to understand the water flow through a crossflow V4

GatorMike

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Aug 3, 2003
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When I opened up the powerhead of my 115 Johnson I discovered definite evidence of some overheating on the left side. Before putting it back together I want to be sure everything is right with the water passages. I have spent the better part of the morning studying the powerhead and trying to understand the water passages and have acomplished nothing but confusing myself. I would like to ask a few questions to help shed light on the subject.

1. I removed the lower unit and connected a water hose to the water tube to locate where water enters the powerhead. When I turned on the water it flowed out of a small rectangular hole on the right side of the midsection to powerhead mating surface. I then set the gasket on top of the midsection and located the hole for the above mentioned rectangle in the gasket. Then I took the gasket in and laid it on the bottom of the powerhead to locate the intake hole. No hole lined up with this rectangular shaped hole. Further inspection revealed a small channel in the midsection of the motor that lead to a tiny hole in the gasket about the diameter of an 8d nail. This hole lined up with a hole in the bottom of the powerhead. Does the powerhead really get all it's cooling water through this tiny hole or am I missing something?

2. The above mentioned hole apears to me to lead into the large cavity in the middle of the block that you can see into by removing the inspection port under the flywheel. It apears to me that hole fills the cavity then water spills over into the space between the inner and outer exhaust cover. Am I correct?

3. At the bottom of the large cavity there apears to be one hole on each side that leads to the passages around the cylenders. I assume that those holes fill the passages then water flows out the holes at top of the cylender heads to the thermostats. I would assume when the thermostats open it lets more water flow out increasing the flow?

If this is correct I just have a couple more questions.

1. My manual has a diagram showing the direction of water flow through the cylender heads. It shows arrows pointing up one side of the head, over the top and down the other side. This makes no sense to me if my earlier assesment is correct and the exit ports are at the top, wouldn't water flow up both sides of the cylender and out the top?

2. There is a small hole (almost a pinhole) at the rubber diverter in the passages between cylender 1&3 and 2&4. What is this hole for and should it be cleaned out and how would I clean it if needed?


Thanks
 

GatorMike

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Re: Trying to understand the water flow through a crossflow V4

Brought it back up for one more try.
 

clanton

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Re: Trying to understand the water flow through a crossflow V4

Where is the pinhole, in the deflector or the block? Replace the water deflectors.
 

GatorMike

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Re: Trying to understand the water flow through a crossflow V4

Where is the pinhole, in the deflector or the block? Replace the water deflectors.

It is in the block. I am not 100% sure it is a hole but there is one on each side of the block. Kind of hard to see but it sure looks like a hole to me.
 

clanton

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Re: Trying to understand the water flow through a crossflow V4

Can`t remember, push a tookpick thru the hole, toothpick should do no damage.
 

boobie

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Re: Trying to understand the water flow through a crossflow V4

Are the water deflectors in the block swelled up? If they are you won't get proper water flow.
 

Fed

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Re: Trying to understand the water flow through a crossflow V4

Do you have the genuine OMC manual Mike, I have one here for a 1988 model crossflow V4 which clearly shows the water flow albeit confusing and a little hard to relate to your description above.
 

petryshyn

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Re: Trying to understand the water flow through a crossflow V4

2. There is a small hole (almost a pinhole) at the rubber diverter in the passages between cylender 1&3 and 2&4. What is this hole for and should it be cleaned out and how would I clean it if needed?


Thanks

Is this the hole you are referring to?
 

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GatorMike

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Re: Trying to understand the water flow through a crossflow V4

Yes sir that is the hole. Great picture, what is that hole for? Mine looks like it might be cloged.
 

petryshyn

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Re: Trying to understand the water flow through a crossflow V4

I would guess its a vapor/air bleed which prevents hot spots. I clean them out with sharpened steel rod in a drill. A drill bit can also be used, but if it grabs and breaks off, its in a bad place...so I use a sharpened welding rod...
 

Faztbullet

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Re: Trying to understand the water flow through a crossflow V4

I would guess its a vapor/air bleed which prevents hot spots.
The hole is unimportant as the deflectors are made from OEM double line fuel hose......
 

daselbee

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Re: Trying to understand the water flow through a crossflow V4

The hole is unimportant as the deflectors are made from OEM double line fuel hose......

You must have read, looked at the pic too Fazt..., the hole in the deflector is not what they are discussing. Deep down in the block, past the deflector...a hole...probably a simple drain for that pocket that is created right there. Lets water out completely. Just a guess.
 

GatorMike

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Re: Trying to understand the water flow through a crossflow V4

You are right daselbee it is deep down next to the deflector. Mine looks blocked on one side and partly blocked on the other. What ever it is doesn't look too important but I will probably try to clean them out with a piece of wire or something.
 

clanton

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Re: Trying to understand the water flow through a crossflow V4

I`m looking at a 97, 115, crossflow water flow diagram. Hard to see on the diagram, but looks like water passage for regulator. I would just clean them, and blow air thru them.
 

GatorMike

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Re: Trying to understand the water flow through a crossflow V4

Ok I finaly pretty much have the water flow figured out. I found an old post by someone who was looking at the same diagram I was and scratching his head. The diagram shows the water comming in at the bottom and flowing around the cylenders and exiting at the bottom. What is confusing is there is no exit hole at the bottom of the block. What they don't show in the diagram is that the water actually exits at the bottom through the two holes in the head gasket then travels up the heads to the exit holes at the top of the heads.


I still can't believe how small the hole that delivers water to the powerhead from the water tube that leads from the water pump is. It just doesn't seem possible to get enough water through that hole to cool the engine. I don't know if I'm missing something, just doesn't seem possible.
 

daselbee

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Re: Trying to understand the water flow through a crossflow V4

Gator Mike...analyze it again. Those small holes both in the gaskets and as pictured in the block are for drainage of the block when the engine is shut down.
I don't know your motor, but going on the general design, and practical common sense, the water flow path must be large, as in the size of the two thermostat to head hoses on a V4 crossflow...that size. Not pinholes.
 
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