Heat Issue - Any Ideas?

[Shallow Minded]

Hey guys, curious if anyone has ran into this before... freshly rebuilt blown BBC. Has ran great all summer, probably got 40 hours on the motor. Last couple of times out, I've noticed the temp gauge get awfully warm (220) the first couple of cycles of the thermostat (140 degree.) Anyway, I shut it back down, let it cycle thru and all has been good. Stays pegged at about 160 degrees the rest of the day. I replaced the thermostat and had the exact same problem last night.
What are the odds of two thermostats sticking in a row? And no, I didn't test the new one before I put it in... darn it. If it is the thermostat, why does it just stick initially and then "work itself out?" If not the thermostat, other possible problems?
Thanks in advance... SM

[kojac]

Shallow minded,
Could be dirt and mud getting caught in your thermostat housing and then flushing out after it get soft from the hot engine water. Had the same problems with a checkmate.
Kojac

[Shallow Minded]

kojac, thanks for the tip. I run in some pretty nasty looking water (Missouri River) so that could definitely be it. Did you do anything to correct this?
SM

[1BIGJIM]

I had the same problem two weeks ago. Belt was slipping on the seawater pump. Floated from Dodge park to Sandpiper. All most ran out of beer on the two hour float :frown: Anyway we could start it just to keep it from hitting shore. Then down by Anchor Inn the belt started turning it again and we drove it back to the dock. Moral of the story keep socket set on the boat

[Shallow Minded]

Revisiting this issue as it was never solved... seems like the problem is getting a little worse. The frequency and heat (per the guage) are both a little more significant. Buddy of mine mentioned the possibility of air getting trapped in the system. Any ideas out there? The thermostat is fine.

[Moneypitt]

What kind of water pump do you run? Any chance the impeller is coming apart and jamming in the system??????Just a thought.......................MP

[Shallow Minded]

What kind of water pump do you run? Any chance the impeller is coming apart and jamming in the system??????Just a thought.......................MP
Standard Mercruiser stuff, impeller was new at the start of the season. I also have a water pressure guage that shows good pressure in the block (15-20 psi.) I'm going to cook the ol' thermostat tonight on the stove...

[infotraker]

I was floating at Rollins Lake near the river opening, lots of little sticks floating around. After leaving the area the temp went up on one side 190 from about 140. It would come and go, ok when going fast. Got it home and flushed with hose, probably sucked up a little debris. Every thing good now.

[paradigm shift]

Anything is possible with thermostats. I would check thermostat in water over the stove with a good thermometer. Then you know it is opening and closing at proper temp.
I usually drill a couple of small holes in my thermostat to make sure air gets purged and no steam pockets develop before opening. 1/16 or 3/32 is what I usually use. If you go too big it runs cold at idle and will not warm up.
Standard merc recirculating system with water pump? Or are you running a cross over? If merc what year is it?

[Shallow Minded]

"Cooked" the thermostat last night and everything looked good. Good idea on drilling a couple holes into it, that should eliminate the air-pocket-theory. I will also try to flush the system as best I can. The water I play in is less than clean...
As for the cooling system, I guess I'm not sure of the difference between a standard Merc and the cross-over set-up . How can I distinguish? Basically, the water comes from the pump, enters a small U-shaped pipe to enter both sides of the block (at this point, there is also relief line that runs back to the top of the thermostat housing), thru the heads, then exits out thru the intake, thermostat and exhaust.
Next year, it's a bass boat... :idea: