your gonna have to take the heads off and have a look.

no.

i have swapped engines and overheating is on the starboard side still with the port engine. I could not swap the headers due to different sizes

Make sure the bypass hoses off the thermostat housing has the water restrictors or a downsized barb fitting inside. Its the hose going to the mid section of the header not the lower water rail of the header. If you have to much water flow there the engine will start to overheat past 4k rpm. Also open up the transmission cooler to confirm there is no sea grass clogged.

im not aware of these water restrictors Would you be able to provide a pic or a link of it?

thanks

doesn’t that mean your problem exists between the water pickup and inlet to engine? Unless I mis-understood

i suppose you could also have a restriction in your headers?

I have swapped those two and removed the ball valve and ran a straight line to test.

the overheating is coming as you gain speed.

over 3k rpm

i am now going through the headers. One has a slight leak and one does not.

I have swapped those two and removed the ball valve and ran a straight line to test.

the overheating is coming as you gain speed.

over 3k rpm

i am now going through the headers. One has a slight leak and one does not.

Dave Wesseldyk has rebuilt many Merc 1075's over the years and he's excellent at trouble shooting the 1075 with trouble codes, etc as the engines sit in the boat.

I've seen several customers bring their boats to Dave's shop with these 1075 engines and he fixes them.

I don't know how much he can help you over the phone, but you can try calling him.
616-308-5119 Wesco Marine in Jenison, Michigan.