07-14-2014 07:42 - edited 07-14-2014 07:44
Your dealer should be aware of the service literature that describes drilling out the gearcase hole 5/16" from the trim tab to the exhaust cavity for more water flow. The trim tab must be inspected and not modified which could restrict water flow. A mention in one of the Service Update books sent to all dealers shows where to drill the exhaust pipe to increase cooling water for the seals if needed.
Engine condition affects temperatures also. Make sure the motor is in a good state of tune and the boat's plumbing is checked for restrictions and air leaks per the training taught in the service schools. Engine mounting height, trimming out too far, and transom obstructions to good water flow into the inlet screens can contribute to the problem.
Your burning the propshaft seals is pretty rare but it does happen occasionally in boats that use jackplates, in some tunnel hulls, and often when operated in water with plant life or debris. Aerated cooling water getting ingested into the water inlets can contribute to the problem. It is not a common problem for normal recreational boating.
Your dealer wanting to pull the powerhead and drilling out the cooling water passage in the inner exhaust housing accomplishes 2 things. It allows more water into the exhaust stream to cool the hot gasses plus the larger hole has less of a chance of being restricted or plugged up when running in sandy or debris laden waters.
Your dealer can test for aerated cooling water by running the boat using a piece of clear hose temporarily attached to the EMM to VST water hose and watching for bubbles at various speeds. In addition, if you have a recent computer printout of your engine, you can examine the EMM temperature profile. If there is a noticable percentage of time within the 120-160°F range or even higher, then that is a dead givaway that the cooling system is ingesting aerated water from the boat or from the motor being mounted too high and sucking air in. Aerated water does not absorb heat like liquid water does. It is similar to a "head of beer" that does not quench a thirst like a mug of liquid beer does. It could also mean that the cooling system is restricted in some way, often from mud, sand, or debris.
You may want to have the above tests and inspections done before going through the time and expense of pulling the powerhead and exhaust system apart.
11-15-2014 07:41 - edited 11-15-2014 07:42
Bill, could he change the type of screens on the lower unit to help with this ? Seems like I heard there are 2 or 3 different types of screens available or I may be wrong and just thought I heard this. If there is a different type available, that may help with the aerated water problem. Just a thought.
If it were an aerated water problem, and that has yet to be determiinedt, then the high flow water inlets are one of the options to help alleviate the cooling situation.