'04 2 stroke 115 TLRC over cooling port bank.

[hevysrf1]

After installing new OEM tstats and gaskets the port bank of my motor will not reach operating temp. Starboard runs about 120℉, port is at ambient.

I'm running on a hose and muffs but in also submerged in a barrel for some back pressure and noise reduction.
I've switched stats from side to side with no change, tested stats in a pot of hot water to confirm operation, and made sure they close tightly when cold.
You can actually feel the cold water from the hose coming to the top of the head when running.
Tstat covers are flat and torqued properly.


I don't know if this was happening prior to the stat change.
Is something in the head corroded thru allowing water to by pass the stat? Externally the motor is free from corrosion.

[panasonic]

Do you have temperature gauge or measuring with laser temp probe?

[99yam40]

OP did you ever fix the problems with rough running back in 7/22?
115TLRC low speed roughness - Yamaha Outboard Parts Forum

[hevysrf1]

Temperature is measured on a Fluke 52II and thermocouples strapped to head.
1200 rpm shake is still there.

[99yam40]

good chance that you have a cylinder not burning the fuel so the head is not heating up

[hevysrf1]

That was my first thought also, but rpm drops on every cylinder when I pull plug wire, timing light flashes on all 4, and it has crisp throttle response.
I've got it in a barrel and I'm not seeing any unburned fuel on the surface.

[99yam40]

too little fuel or too much will keep the cylinder from burning the fuel.
Monitor the plugs on each cylinder to see if one is lower temp.
burning fuel creates heat

[hevysrf1]

Thanks, I'm going to try to confirm that the port bank is actually making heat.

My idea is run the engine with the port stat cover off,
stat out and a hose inserted into the stat hole to divert the water flow overboard, should heat up pretty quick.

[hevysrf1]

Is the water stream coming from the lower hole backing up from the poppet?

[panasonic]

Correct me if I am wrong. I don't think water should be gushing out of that hole. Thermostat should open and let water through and go back out through the other way to those passageways to the head.

In other words the water should be coming through the thermostat and back out through that hole you show in picture? Hard to visualize without seeing it first hand.

You could take off thermosat on other side that is heating up and see if is the same!

[hevysrf1]

I'm not sure about water coming out of that hole either. But at this point it starts easily, idles smoothly and ev revs nicely in the barrel, its going back together and I'm just going to splash it and run it.