Portside running cold

[bondobill]

Hi all, new guy here
Engine 97 Yamaha 200 2 storke carbureted, 200 hours on factory new power head
Boat run strictly in salt water and flushed after every use

What else besides t/stats would cause one bank to run cold. Port side is running low 70s and the starboard side runs around 120 degrees. This is with engine running on muffs. Replaced t/stats with the factory replacement....service manual says 118 degrees t/stat. With new ones port side still running cold. Numbers are the same as with the old t/stats. Tested new stats in warm water and they appear to be functioning properly.
I did a compression check and all appears good there.
Port side plug where black, sooty and wet.
I looked at where the stat seats in the head cover plate. It showed some signs of corrosion and pitting. I cleaned that up and used a little gasket sealer around the seat and still no change
Any one ran across this before

Thanks

[zenoahphobic]

"port side plugs wet black and sooty" sounds like the is an ignition failure on that side.
Cold is because fuel is not burning and nothing to do with thermostat.
I'd start by checking for spark, firstly with timing light whilst running, then statically, pull out all plugs (including starboard side) earth all properly, crank and see if they all spark.
Depending on what you see or don't see will determine further what you should do.

[bondobill]

Thanks Zeno
If it is a ignition issue could the engine even run with the port side not firing ?

Only issue I have had with engine performance wise is...the last couple time out I noticed I had to choke the engine to restart it after *****ing around on my kicker motor for a couple of hours. Normally after the engine was turned off after running out in the morning I could hit the key with out choking and she would fire right off. Now the last couple times out I need to choke it to restart it. Then it runs a little rough at idle and dies a time or two until it warms up. After a minute or two of warming up she runs like a champ all the way back home.

[zenoahphobic]

If engine runs fine after awhile then your ignition electrics are functioning.
It seems your engine is running very rich at startup and hence not firing at port bank.
I wonder if you can test the temp of both banks immediately after they are running fine and eliminate your thought about running cold.
I would now check the carburetters for problem, floats come to mind. The port bank there are two, I suspect only one has a problem.

[bondobill]

Update

I pulled the head cover plate on the port side to see if the gasket was bad
Gasket was toast


Section of gasket was gone around where the t/stat seats


Cleaned it up, installed a new gasket. Ran her on the muffs for 10 minutes or so. Port side warmed right up. Checked temp with a laser, both port and starboard banks running right around 115. Looks like we got it

Thanks guys
Bill

[zenoahphobic]

*** that sure is two different looking heads. So it would appear a large part of the cooling water went to the left bypassing the thermostat.
I'd worry about the quality of that rebuild.
It may have also been that the torque on the bolts were not checked after running sometime after the reassembly.
Good to you are up and running and thanks for the feedback!

[bondobill]

*** that sure is two different looking heads. So it would appear a large part of the cooling water went to the left bypassing the thermostat.
I'd worry about the quality of that rebuild.
It may have also been that the torque on the bolts were not checked after running sometime after the reassembly.
Good to you are up and running and thanks for the feedback!

Sorry bout that.
The head cover plate on the right is a spare I had from my old 89 225 Excel
I dug it out in case the port side cover plate was shot.
I would dare to quess the bolts where never retorqued after initial start up. So far I have had to replace both head gaskets....they where weeping water to the outside of the block. I could tell cause none of the bolts showed any signs of a wrench or socket ever used on them.

Bill

[zenoahphobic]

200 hours on a factory rebuilt power head meticulously flushed should not have the gaskets fail, unless they just replaced the old entire head and never removed the water jacket. So I would also do the starboard side.

I recently did my 175 water head jackets.
Interesting the difference between the 200 (same as 175) and the Excel. At the bottom the excell has the silly passage removed, I wondered about mine as it was also a point where corrosion and rubbish builds up restricting water flow.