found this old thread
ealers dont know of this bulletin from mid 1980 but my 1974 Well Craft heats up and I throlttle back and is fine. anyone know about this water reversing Kit it mentions or how fix the problem?...
"Mercury found a lot of the in-line 6 engine manifolds were cracking and were unable to identify a cause. Investigation found that the problem occurred when a boat had been running for a while and was suddenly bought to a stop. What they found was that because the water entered the manifold at the front, when the boat's bow was up an air pocket would be created at the top of the manifold at front, near cylinder #1. With no water there this area became extremely hot. When the boat came off the plane, and sat more level, water would suddenly fill the void and crack the casting.
To overcome the problem the Merc engineers came up with a very clever fix (I think it's clever). They changed the direction of the water flow in the manifold and effectively forced the water to flow 'uphill' when the boat's bow was up. They did this by changing some parts and adding a couple of hoses.
1. Remove the short hose from the thermostat housing to the front of the manifold and replace it with a hose that goes to the back of the manifold.
2. Replace the blanking plate at the back of the manifold with a plate the same as the one at the front of the manifold. It has to be mounted sideways.
3. Remove the exhaust elbow and fit a blanking plate over the water galleries between the manifold and the elbow. Has to have a small (1/8") hole for air bleed.
4. Remove one of the plugs on the side of the exhaust elbow and fit a 90 degree brass fitting.
5. Run another hose from the brass fitting to the port plate on the front of the manifold.
6. Pat self on the back for a job well done
It came out as a service bulletin in the mid 80s, but I can't find a reference to it anymore. I had to replace the manifold on my old 165 and the kit came with the new manifold, complete with installation instructions"
I sure hope someone knows about this. Shez really a good old fishing boat I want to fix her. Dont think anything has happened yet cause no water in the oil.
HARRY
ealers dont know of this bulletin from mid 1980 but my 1974 Well Craft heats up and I throlttle back and is fine. anyone know about this water reversing Kit it mentions or how fix the problem?..."Mercury found a lot of the in-line 6 engine manifolds were cracking and were unable to identify a cause. Investigation found that the problem occurred when a boat had been running for a while and was suddenly bought to a stop. What they found was that because the water entered the manifold at the front, when the boat's bow was up an air pocket would be created at the top of the manifold at front, near cylinder #1. With no water there this area became extremely hot. When the boat came off the plane, and sat more level, water would suddenly fill the void and crack the casting.
To overcome the problem the Merc engineers came up with a very clever fix (I think it's clever). They changed the direction of the water flow in the manifold and effectively forced the water to flow 'uphill' when the boat's bow was up. They did this by changing some parts and adding a couple of hoses.
1. Remove the short hose from the thermostat housing to the front of the manifold and replace it with a hose that goes to the back of the manifold.
2. Replace the blanking plate at the back of the manifold with a plate the same as the one at the front of the manifold. It has to be mounted sideways.
3. Remove the exhaust elbow and fit a blanking plate over the water galleries between the manifold and the elbow. Has to have a small (1/8") hole for air bleed.
4. Remove one of the plugs on the side of the exhaust elbow and fit a 90 degree brass fitting.
5. Run another hose from the brass fitting to the port plate on the front of the manifold.
6. Pat self on the back for a job well done
It came out as a service bulletin in the mid 80s, but I can't find a reference to it anymore. I had to replace the manifold on my old 165 and the kit came with the new manifold, complete with installation instructions"
I sure hope someone knows about this. Shez really a good old fishing boat I want to fix her. Dont think anything has happened yet cause no water in the oil.
HARRY
