Fuel Sludge on Thermostat

[WhiskeyGun]

Model: J140TLESE, 1990 140hp

Story:
I had discovered my motor was running a bit cold on the starboard side. After running around in the boat for a few hours and continuous at last 20 minutes, I checked by placing my hand on the heads. Portside I could hold for a bit and seemed good. Starboard was barely warm. Other than that it ran pretty good. It did sneeze some idling back to the ramp. I returned home and flushed it with some clean water and again starboard side wasn't that warm. Anyways, I pulled the thermostat out and took it apart. I discovered what appeared to be red silicone wrapped up in the spring and vernatherm. Only place I've seen red silicone was on the water pump seal. I had a fun time cleaning that up when I replaced the water pump a couple years ago.

I tried flushing it (nothing really came out) and I bought two new thermostats and replaced them. Well after replacing them and running the boat on the muffs I measured the temps with a laser temp gun. Portside stayed around 120* and starboard was now 145* on top cylinder and 170* on bottom!! Way hotter than before. The water out the tell tale was pretty warm (usually cool). Well, I went to pull thermostat out again and this time I discovered a grey colored liquid all over the side of the thermostat that feeds into the little hole towards the block (cap and seat according to diagram). There wasn't any on the other side towards the thermostat cover. That grey stuff smelled like like gas! I took a whiff inside the thermostat housing and it reeked of gas.

I ran out of light but I will do a cold compression test (scared to do warm now). I did a warm check last July back when I was diagnosing an earlier issue they were 90 90 90 80. I believe 80 was on the cold but now hot side.

Has anyone ever experienced this or might have an idea how gas could get on the front side of the thermostat? Just trying to understand all the possibilities of how this can occur. Will/Should I need to pull the head off and take a gander? I took a peek into the cylinder with plugs pulled out. The plugs looked good and were not wet or anything. The bottom cylinder was clean, but the top had a bit of carbon but not a whole lot. I didn't see anything that signaled water getting into the chamber.

I just want to know the possible ways fuel would get up there or into the water system. Is it possible the head gasket is leaking now? Perhaps near the thermostat seat?

Didn't have any gas in there until after I changed the thermostat :-(.

 

[boobie]

Get the motor off of the muffs, put it in the lake and run the hell out of it and then see what you have.

 

[oldboat1]

was thinking you could suck up some exhaust stuff (i.e., unburned fuel) if running in a barrel -- but maybe on muffs too. In any case, can't get a good sense of operating temps running on muffs. Agree with boobie -- Take your temp gun with you, and hit the lake.

 

[WhiskeyGun]

That was my original plan, I was going to run it on the water to ensure it was actually working right and to "break it in". It just seemed kinda strange to get some fuel there.

 

[WhiskeyGun]

Can you edit posts? Anyways I wanted to know, how hot is too hot before I run it again?

 

[oldboat1]

The motor shouldn't be run over 160 degrees F on the top of the head(s). If you find yourself at that temp out on the lake, you can probably ease your way back home, but that's been the upper limit for years. If you are smelling something hot and you are scorching paint, it's probably quite a bit hotter than that -- but don't want to get there.

I'm not sure where you are getting that 170degree temp. The face of the cylinders will get hotter than the top of the head.

 

[WhiskeyGun]

I've got a stout trolling motor just incase ;-). 170 was measured on the bottom starboard head around the plug area. I got a lot of variations checking different spots, anywhere from 160-180 on the bottom. I couldn't hold my hand on it like I could before.

 

[WhiskeyGun]

Got a chance to run it on the bay yesterday. The temps on the starboard side stayed around 140-145* whereas port side 120*. T-stats open at 143*. While running at 3500-4500 rpm the motor seemed to run pretty good. WOT after a couple minutes it starts to surge a bit, backed off a small amount and returns to normal. It didn't idle like normal either and even died once. Sounded like it wasn't firing like it should (much quieter than usual).

I am wondering if that is why I was getting fuel sludge on the thermostat as its not burning the fuel. Might also be why the port side doesn't seem to get hot enough. When I went to load up the motor died and it wouldn't start afterwards. Got it out of the water and you could smell gas like it was flooded. Took it home, started no problem and flushed it on the muffs.

Been thinking about taking it to a boat mech. The one I talked to said he'd charge me $85 for a look at it along with a link and sync. Any other ideas before continuing on?