Cooling system flow chart

[Robert.E]

If i understand this flow chart it shows that water comes from the
stern drive goes to the engine water circulation pump and then in to the
engine..When the water temp rises, the thermostat will open and
pass water to the exhaust manifolds..

My problem is that the left exhaust elbow is mutch hotter than the
right one.Since the water that flows to both manifolds passes thru the
same thermostat then it cant be a water pressure problem can it ?

I?m just making sure that i dont have a water flow problem before
i order a new set of manifolds.

 

[Don S]

Re: Cooling system flow chart

You also need the diagram of the thermostat housing to really understand it. There is ALWAYS water going to the exhaust manifolds. the thermostat only holds the water stationary in the engine till it gets warm and opens allowing the circulation pump to push water thru the engine.

 

[bruceb58]

Re: Cooling system flow chart

I know on Volvos, the manifold on the port side of the boat runs hotter. I thought that with Mercs it was the opposite.

When you say left, do you mean left as if you are facing forward in the boat or looking towards the rear looking at the motor?

 

[Robert.E]

Re: Cooling system flow chart

Towards the rear looking at the motor

 

[Don S]

Re: Cooling system flow chart

This is a boating site. Port and starboard always works.
When you say hotter, how hot? Is this on muffs or in the water? When was the last time the raw water pump impeller was changed. How old are the manifolds/risers.

 

[Robert.E]

Re: Cooling system flow chart

Its in water. I will probably get burned if a rest my hand on it for 3 seconds.
The other one i have no problem resting my hand on.

The impeller was changed quite recently. I dont know how old my manifolds are.
I took them apart today.

 

[Robert.E]

Re: Cooling system flow chart

This is a picture of the exhaust manifold

 

[Don S]

Re: Cooling system flow chart

I wish you hadn't pulled it apart just yet. You could have raised the rpm up to about 1200 rpm to see if it cooled it down or not.
I SEE nothing wrong with the manifold from that picture, but you need to check the riser. Especially the passage the water comes out of, and see if it's blocked.
Do the risers look like they are the same age?

 

[Robert.E]

Re: Cooling system flow chart

Yes the risers look like they are the same age.

I have been trying to clean the risers where the water comes out.
I think i have managed to get some rust out of it.

When i first noticed that i had one exhaust elbow that was hotter than
the other i had been running at 35mph for about 10 min.The "healthy"
one coold down quite fast but the other one was to hot to touch.