1983 AQ225D cooling issues

[rokknrobb]

1983 AQ225D with half closed system, AQ280DP drive.
My engine seems to be running hot, the temp gauge says 190-200 on the water under load and is about 160-180 at idle in the driveway with muffs.
so far I have replaced:
manifolds and risers
impeller
raw water hose and cover on drive
Thermostat and cover
hoses that looked old
back flushed heat exchanger and other hoses
there is a good water flow coming out the transom from port side, the starboard side does not, and the manis and riser are running a bit hotter on that side.
I did find debris like what looked like rust chunks in some of the hoses but i cleared all of it.
Last time i went out the gauge said it was 200 plus but there was no sign of over -heating but when i backed off the throttle after 30 mins of constant pressure she started overheating from the radiator over flow.
After it cooled down it started back up and ran the rest of the day.
I had it in to my mechanic years ago and asked why the gauge showed excessive heat and he said he didnt know why? He said it showed no sign of heat or over heating? He mentioned maybe a bad gauge, he also didn't know why the out flow from the transom hoe was better on one side than the other.
I bought digital heat check at harbor freight and the manifolds are runnig about 120-122 and 127 on the starboard, not sure if thats excessive, thats in the driveway with the muffs.
Any help appreciated in advance

 

[alldodge]

Use the temp gun on the thermostat housing and match it to the boat gauge. Could be there isn't an issue

One side of the exhaust will always be different then the other, ts just the way water flows inside the exhaust. Your temp readings look fine

 

[Scott Danforth]

have you checked the raw water casting on the top of the swivel on the outdrive? if that is corroded, it will over-heat in the water when underway, but not on the muffs.

 

[rokknrobb]

If you are referring to this, I replaced it was in bad shape

 

[kenny nunez]

If the engine still over heats then you may be getting air from the “O” ring that seals the lower to the mid section when the boat is planing.

 

[Scott Danforth]

yes, that is the fitting that will rot away in fresh water in about 5 years or salt water in under 2

and yes, Kenny is right, if there is any corrosion where the swivel shaft is sealed on the lower/mid section, it will suck air

the only way to repair that is to separate the halves of the drive, address the corrosion and get the seals/o-rings needed to put it all back together.