Uneven Cyl. Head Temps (1990 Johnson GT200)

[27E_20]

So I just happened across this forum while Googling around. Unlike iboats or even Scream and Fly, this forum has several threads directly related to my motor: 1990 Johnson GT200 (VJ200SLESE). I have found several helpful threads already.

However, I am struggling to come up with an answer to my current motor issue. At idle, whether in the lake or on the muffs, the difference between the two cylinder head temps is a little extreme. Port side idles in the upper 150's while the Starboard side idles in the lower 100's. What is even weirder is when I get up on plane, the port side drops to 130-140 while the STBD side rises to 120-130. (All temps vary with water temp).

It should also be known that I did away with the water control valve and "upgraded" the thermostats last fall. Temps were checked with a recently installed gauge and verified with a calibrated IR temp gun.

What I have done so far:

Replaced Port t-stat with brand new one
Swapped Port t-stat with STBD t-stat
Installed original t-stat back into Port side
Removed Port Cylinder Head, removed a small piece of plastic from t-stat intake, replaced with new gasket, ensured water flow through cylinder head.

Nothing changed. (thought the piece of plastic was the culprit).

Question is: Do I even need to be worried about the temperatures or the difference between the two? OR is it something more serious? Spark plugs are very oily, so Im running rich. Spark checks out OK but could be intermittent? Compression is right at 90 on all cylinders.

Take a look at the pics and see what you think.

Piece of Plastic.jpgPort Cyl Head.jpgPort Cylinders.jpg

Video of Temps:

[Bassmeister]

From the looks of two of the cyls on that head, you have water intrusion...IE: steam cleaned .....Check the head gasket for any signs of leakage. When the engine gets up to speed, the pressure will blow the 'stats open creating a more uniform temp range.....and lower for a wot engine.

[27E_20]

Check the head gasket for any signs of leakage.

There was a spot on the old gasket where it looked like water COULD have got in (around one of the bolt holes), but the metal rings were intact.

Anyway, I replaced it with a new one - no change.

[Bassmeister]

That's an open deck engine, and I didn't see any deflectors present......from this point, I'd have to defer to the gurus......

[27E_20]

Any OMC gurus around? I cant imagine I am the only one who has had this problem. Then again, it would be just my luck...

[ChampioNman]

Any OMC gurus around? I cant imagine I am the only one who has had this problem. Then again, it would be just my luck...

Nope Fourth of July weekend we get vacations too. I will tell you this much there are no water deflectors in your block. But then again most folks don't mess with the power boost cooling system either.

[Jewn.beef]

Dont know if is normal or not but my 97 225 venom is running 135 on motor starboard side which is boat port side And the motor port side is running 105
this is at idle just after 10 minute wot run

[27E_20]

Nope Fourth of July weekend we get vacations too.

I understand. This is the first holiday I have had to work out of town in a while so these are how my nights are spent in the hotel room - worrying about an old boat motor.

Beginning to think its not that big of a deal. Still runs real rich, so not too worried about melting any pistons.

Thanks for the input guys.