#3635, "RE: Why do powerheads and lower units always break" In response to In response to 0 Wed Oct-14-09 03:54 PM by Sacto John
They are the most stressed part of the motor...well those two things together basically make up the motor. I think power heads blow so often on outboards, especially on bass boats, is due to the amount of time the motor is ran at or near its maximum operating RPM. How often is a car's engine or even another two cycle engine (dirt bike, lawn mower)ran as hard as boat's out board? That said some outboards will last forever. The 1974 Evinrude I have on my boat has never been rebuilt and still has almost factory compression.
Lower units go bad for much the same reason, their parts are run at close to their operating maximum most of the time. Lower units are also subject to other abuses such as being struck by objects, or fishing line wrapping around the prop and destroying seals. Lower units are the lowest point of the boat when it is in the water most of the time and they are often hit buy hard objects at varying speeds. All it takes is one gear tooth to get out of alignment or broken to grenade a lower unit.
As for prevention, its just like anything else: frequent preventative maintenance and sensible running of the motor. Service your lower unit every year, and have your motor serviced as regularly as the manual suggests. Little things also help. Put fuel stabilizer in your tank if you know the boat may sit for a month, run ring free (or whatever Mercury calls it) every third tank of gas, check your lower unit seals and oil between services. Find a good mechanic that you trust and ask him what he might suggest.
Most importantly, pay attention to you motor, get in tune with it. Know what it sounds like when it is running good, shut it down if you sense something is wrong. I have owned numerous boats since I was sixteen years old and have never blown a powerhead, or had a lower unit fail, and all of my boats were older and well used.