bshellrude
Seaman
- Joined
- Jul 26, 2004
- Messages
- 66
Hello all:<br /><br />If you've followed some of the other posts I've made you'd know that I have just rebuilt the power head on my boat.<br /><br />Now, here is what's hapening during break in. Yesterday, put boat in water to begin 4 hour idling... all went well, rough idling for the most part but ran well. Finally, after idle time, began running on open water without bringing throttle past 1/2... after running like this for about 45 minutes at varied RPMs, I received an every other second alarm leading into a constant alarm. When placing my hand on the cylinder head, it was certainly hot, but not hot enough that I couldn't leave my hand on it for a second or two (i.e. not hotter than the hot water coming from a tap).<br /><br />So, I'm wondering if this is a thermostat problem? Highly doubt it being a water pump problem (FYI - replaced impeller, pee-hole stream good and strong, etc...). The other thing I'd heard is about airlocks forming by the top cylinder in these types of engines.<br /><br />So my question is basically this. Why would it run fine without warning for 4+ hrs, and then all of a sudden go into an overheat condition? Further, why would it give an every second alarm leading into a constant alarm? Are these symptoms more indicitive of an airlock as opposed to thermostat? Or malfunctioning thermostat? Or combination?<br /><br />Cheers,<br />Ben