V-6 Temperature Inconsistency..Overheat?

[Randy W.]

I have an extreme difference in temperature readings between the port and starboard banks on my 1980 200hp Johnson. In cool 65 degree outside temperature, using a laser temperature tool, the port side is running at about 92 degrees, starboard at nearly 150 degrees after 15 min. idle. Here's what I've done.

1. Changed gasket in head and all passages appeared clear on the starboard side.
2. Installed 3 new water diverters and new head gasket on starboard side.
3. Installed 2 new thermostats.
4. Checked flow from both thermostat openings..starboard/port...appeared strong and equal on both sides.
5. Installed new impeller 2 months ago, tell tale stream very strong (I know this doesn't tell us anything about block flow). As previously mentioned, flow was great out of thermostat openings.

What have I missed? How come the port side temp. is so low? Would there be an obstruction after the head on the starboard side before the water exits?

 

[Joe Reeves]

Re: V-6 Temperature Inconsistency..Overheat?

Assuming that the new port thermostat is functioning properly, I would be looking at the port nylon water bypass seal (somewhat melted?) and also inspecting the rubber seal seat for it.... they (rubber seat) have been know to come loose and drop out of the way, possibly unseen by some previous owner/individual when changing a thermostat at an earlier date. Should this be the case, water would flow freely thru that thermostat area.

 

[Randy W.]

Re: V-6 Temperature Inconsistency..Overheat?

Joe, thanks for your response. I'll take the thermostat cover off and reinspect that area. I guess if the starboard side stays at 145-155 degrees, the real concern is on the port side with the low temperature. It sounds like water is potentially flowing right past the thermostat unchecked if that seal is missing or damaged?

 

[Joe Reeves]

Re: V-6 Temperature Inconsistency..Overheat?

You asked: "It sounds like water is potentially flowing right past the thermostat unchecked if that seal is missing or damaged?"

That is correct. The thermostats on the starboard side open at some figure around 143?/148? (somewhere in that range) so the running temperature may be slightly higher than that.

Of course this pertains to the port side also but that is where the problem lies.

 

[Randy W.]

Re: V-6 Temperature Inconsistency..Overheat?

You asked: "It sounds like water is potentially flowing right past the thermostat unchecked if that seal is missing or damaged?"

That is correct. The thermostats on the starboard side open at some figure around 143?/148? (somewhere in that range) so the running temperature may be slightly higher than that.

Of course this pertains to the port side also but that is where the problem lies.

Thanks again Joe. I'll be digging into that port thermostat area and snoop around. I'll let you know what I find. Randy.