250 Opti, 1B961164
I've had this motor for going on 9 seasons now. Put 800 hours on it before the compressor took out the fuel injection system last May. Went with a full dress reman powerhead. However, since then, keeping the thermostats clean and functioning has been nothing but a headache. Prior to the reman, I never once had to clean them in 800 hours. Not once. Why after the reman would they all of the sudden be so susceptible, especially to a little sand grit? What has changed?
There was a time that I didn't fish but I cannot remember it.
Having had many Mercury 3.0L DFI motors, I had one that was a vacuum cleaner and picked up a lot of junk in the thermostats. Others never picked up anything. I am not sure whether it was coincidence or just luck.
USN Retired
2020 Basscat Caracal
2020 Mercury 225 ProXS 4s
The design and flow pathways did not change.
Either the cleanliness of the waterway has changed, or you have changed where you operate (or launch/pullout).
One of the most common items we see is folks that leave the engine trimmed DOWN while on the trolling motor. Trim that thing up to keep it off the bottom: It absolutely DOES make a big difference!
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
No changes in my seasonal routine since the new powerhead. As far as waterway changes, I fished 26 different bodies of water last year after the new powerhead which is typical for me. Everything from major rivers like the Mississippi to 70 acre lakes with all manner of boat ramps from concrete, to sand, to gravel and all manner of lake bottom substrates and submergent vegetation. I do keep my motor trimmed up when fishing shallow, more so because I don't want to ding the prop than anything else. If we're going to talk about changes, to me the elephant in the room is the new powerhead.
There was a time that I didn't fish but I cannot remember it.
I can understand what you're saying- but the powerhead isn't where the debris is coming from. It's coming from the water inlets, which in turn are pulling debris-laden water in from the waterway(s).
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
Which to my mind (such as it isOriginally Posted by EuropeanAM
), leads to the thermostats. Has there ever been any variation in sourcing or quality over the years? Does Mercury manufacturer them in house? Any slight lack of quality or variance during a span or two that would lead them, as in my case, to not close due to small amounts of contamination? More than once I have cleaned them without seeing anything visible to the naked eye.
There was a time that I didn't fish but I cannot remember it.
There have been a couple of vendors that manufactured them over the years- but no real significant change in the shape/size/function.
The biggest change that occurred was tighter tolerances in the thermister (which actually improved function).
From the very early days- a tiny pebble, several grains of sand, or anything that held the valve open MECHANICALLY by any amount could result in cold operation.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
Thought I'd update this thread since I too get frustrated when I find one that matches a problem I'm having and the resolution or update is never posted. I've put exactly 40 hours on my motor since last having to pull and clean the thermostats (June 2022). I'm obviously a complete amateur when it comes to this stuff but I just have to conclude I was dealing with some sort of residue left over in the powerhead cooling system after the reman process since I did not replace the thermostats. Anyway, nothing in my routine has changed and I'm still fishing a wide variety of lakes and water conditions. Hope this helps someone and I didn't just jinx myself.
There was a time that I didn't fish but I cannot remember it.
glad its doing good
.................................................. ...the scariest thing in life is the unknown ...................................
Me too
Last edited by Macsimus; 03-15-2023 at 08:50 AM.
There was a time that I didn't fish but I cannot remember it.
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