boat has motors installed, motors run strong for 2 to three hours, then one seizes up......... this has happened twice, last time was yesterday during poker run.........

It almost feels like motor is hydro locking, but it seems to happen at 3500 to 4000 RPM's, while running 50 to 60 mph, so it does not happen when hammering down on the motor, or from ingestion.

Motor has lightening headers, everyone (several merc techs in area) seem to think it is the headers (they are new, probably 10 hours run time), but it does not make sense to have reverberation at those rpm's, or does it? (Mechanic will pull plugs tomorrow to see if water is present.)

If you have ideas I would sure appreciate them, the last motor to go down was a new GM crate motor with 2 hours on it. The one before that was built by a well respected local engine shop who is a close personal friend and who, for outside reasons, baby-sits my stuff closer than any imaginable. So far this problem has cost thousands and thousands of dollars.



Second question, if there is water in cylinders, then headers are faulty, does lightening warranty against damage caused by faulty headers?

Dean,

You will not have reversion problems at that rpm. Once off idle, reversion becomes a non-issue. Something else is happening here. When the engine locks up, what makes it unlock? Time sitting and cooling?
If you suspect water in cylinders at that rpm, you may have an intake or head gasket problem. Or maybe a cracked head or block. How much water pressure do you have at speed? When the engine is locked, have you tried to pull the plugs? If you do and water gushes out, that would tell you right away its water ingestion.

Vinny