Johnson 90HP 1990 Port side over heating

Hi,
Looking for a bit of advice to do the least work possible and save some dollars!
The port side horn goes off after about 10 minutes running, WOT and half WOT. Each time it goes off, I stop the engine, let it cool for a few minutes, turn the key on - no horn, I fire it up and go half throttle for say 5 minutes and the horn goes off again.
I have a temp gauge - sender is on starboard head and is in the middle. I know it is the port head because if I disconnect the horn - it stops!
I rebuilt the engine about 8 years ago, only done about 40 hours, haven't used it much in the last two years. Compressions are good 1 & 2 = 125psi, 3 & 4 135psi Jan 20, changed the impeller went out a few times all good. Jan '21 - fired it up on the muffs and the horn went off after a bit. I pulled the water tubes from the heads to the stat housing to flush some water through, connected up and did no horn! I didn't take it out.
Two weeks ago went out and the horn went off after about 10 minutes. Change the stats for new ones, went out again, same thing. after about 10 minutes running, WOT and half WOT. Each time it goes off, I stop the engine, let it cool for a few minutes, turn the key on - no horn, I fire it up.

I have read a lot of articles on this - bought an infrared temp gauge, got a tank of water and ran the engine - water was 2" above the cavitation plate. Tell tale water was strong at idle, left it idling for 10 minutes, no over heating. I aimed the infrared temp gauge at the spot where the horn senders are in the head - starboard 135 degrees, port 150-152 degrees. So I guess running temp may go up say 10 degrees which pushes port into horn territory!
So should I pull the water cover off the port head first and check for obstructions? Then if nothing obvious pull the head?


Thanks

Check your water deflectors in your block.

Thanks Boobie. I have just pulled the port side water cover and found that salt build up between the gasket and cover plate has blown the gasket into the cooling channel.
I run the engine in salt water and flush on muffs for 5 minutes. I thought that I did a good job, clearly not! I might have to use salt away.
Cleaning it up and waiting for a new gasket, then will test - more later

You may want to pull the head on that side and check your deflectors.

Let us know when you find out something ????

Like Boobie said... Water Deflectors.

Hello, Joe, always great to hear from you. Gotta use my last 15 horse carb, I got from you....going down to Texas next week....with a 9.9 Johnson attached to it. Thanks, my friend.

Rude, what did you ever find out ??

I'll ask one more time. What did you ever find out ????