Intermittent overheating problem

[papdetomaso]

Gentlemen, I have a 1969 OMC 225 ci Buick V/6, it's cooled by lake water (fresh). Boat runs great and will not overheat while on plane. Once in a while at a wakeless speed the temp will climb to 200 degrees, and sometimes at idle and out of gear it will do the same. The next day it will stay at 160 degrees all day. Which is most likely to be intermittent...engine water pump, thermostat, or impeller...thanks...Rich

 

[dahman01]

Re: Intermittent overheating problem

I dont know for sure but i can tell you that my uncle had a prob. like yours and his was the lower unit so might be something to look in to like i said though not for sure just a thought.

 

[novelles]

Re: Intermittent overheating problem

I would check impeller first. If it is too bad, it might be able to push water up when at high RPM's (some water escapes and falls but still enough going up) but not at lower (water escapes and falls down). If temperature is stable at high RPM's water pump and thermostat work fine.

 

[tommays]

Re: Intermittent overheating problem

well its over 30 years old which is a long time even for a fresh water motor. i would check the thermostat first and see what kind off rust and scale has built up in the motor. on my motor i have had small pieces get caught in the stat and start to catch more and more almost like a filter the motor would get hot and it when it was shut down they would fall away and allow normal flow again after i cleaned it out a few times it has been fine<br /><br />but with out knowing the service history of the boat it a wild guess at this point<br /><br />tommays

 

[Bondo]

Re: Intermittent overheating problem

Mine does that now,+ then.......<br />River Silt jambing the T-stat........<br />I troll for Hours on end... When it climbs to 190*/200*, I'll just bump the throttle abit till it begins to Cool....<br />Then return to Idle.........

 

[papdetomaso]

Re: Intermittent overheating problem

Thanks for the replies... I've had the boat for fourteen years and haven't replaced the impeller, I have replaced the thermostat once a few years back...so I guess it's time to get the tools out....Spanishboy, I have been to Mallorca and it is a beautiful place...I'll let everyone know what I find out...thanks..Pappy

 

[kayakndave]

Re: Intermittent overheating problem

It could be a bad sending unit as well......

 

[f_inscreenname]

Re: Intermittent overheating problem

Ya before you get to far ahead of yourself I would check the gage also. They don't always tell the truth.

 

[Bondo]

Re: Intermittent overheating problem

I've had the boat for fourteen years and haven't replaced the impeller,

Ayah,<br />You're about 12 or 13 Years Over-Due........

 

[rodbolt]

Re: Intermittent overheating problem

I am with Bondo

 

[papdetomaso]

Re: Intermittent overheating problem

The gauge and sending unit are new within the last three years with a good ground. I'm going to replace the T-stat first and try to get lucky. But as Bondo said 12 or 13 years Over-Due...guess I've been on borrowed time...thanks...Pappy

 

[novelles]

Re: Intermittent overheating problem

Go directly to the impeller. T-stat opens or not or more or less accurately but if it cools down when at high RPM it is opening far enough. Most T-mast die in the open position and the problem is that engine does not get the right operating temperature.<br /><br />If you keep cruising like that, you will end up overheating some day.