mercury 40hp 4cyl oil injected overheat alarm

hey all I'm new to this site. and I'm hoping someone could help me out. I have a mercury 40hp 4 cylinder 2 stroke oil injected about the 1995 model. I have this issue where if I go 3/4 to wot my overheat alarm goes off. then I back it off and it goes away. I can go just under 3/4 throttle all day with no issues. I've tested my overheat sensor by grounding it out and it will buzz. I've replaced the water pump with no luck. I've pulled off the powerhead and replaced the gasket between powerboat and midsection as it looked like it was leaking with no luck as well. I can put my finger over the tell tale and its warm to touch. this model does not have a thermostat and I also think its got no popet valve and if it does where would it be. I would love to solve this problem. I have searched everywhere on this forum and other sites with no luck. I'm sure someone has fixed this problem as other people have the same issue as me. any help would be greatly appreciate. hoping to solve my problem.

No thermostat or poppit valve on those.----Did you look check for damage to the fitting at the top of the water tube ?---Was the old impeller damaged ?---If so did you find all the pieces ?

yea checked for damage to top of water tube wen the power head was off and the old impeller looked new still. no missing pieces off the impeller

I've noticed on all forums no one likes helping out newbies. makes me wonder why people like to hold out on knowledge or give a totally wrong answer. but I can see why people don't bother to help as most people only want one thing is to help themselves and not contribute back to the forums.

?---When did you get " wrong answers " ?

I wasn't talking bout u racer one u are dead on with what can happen but If u read my post I changed the water pump which meant looking at old impeller and I did replace gasket between powerhead and mid section which meant looking down the mid section for corrosion and anything different about it. I did read someones post hear too and they also have exact issue as me but he also had no reply. someone must of had same issue on this particular motor as I have read lots of post where they too have exact problem but no one seems to have an answer. please someone help me. I really like my motor I think its got good performance. and decent fuel economy for a 2 stroke. all I know is this motor has been like this 2 owners before me and I know its been to the mechanics as I do have some receipts for a lot of the work that has been performed on this boat. I've even taken it to the mechanics and he too could not help me. please any info would be greatly appreciated. thank you for reading my post and I hope someone can help me fix my problem.

Bring it over along with some coins, I think I can fiks it for you.

I live in Australia. Would b cheaper if i buy a new motor. Wouldn’t b viable to post boat over to u plus im mechanically minded. I love pulling motors apart and put them back running again. Even if u fix for free and pay for parts it not worth posting to u. I have two marine mechanic with years of experience and one lives a bit far and he works fulltime which means he doesnt have time to diagnose for me. The other has had an attempt to fix with no successs. And he is lost for words atm. The mechanic that lives far from me had the same motor for wrecking and wen i was over there we pulled it apart to see wat mite b the problem but could not find a solution. Ive thought bout rebuilding it but wat if i run into problems such as snapped bolts which would turn into a nite mare. Im sure someone has this issue as its very common fir these 40hp 4 cylinder oil injected to have this issue according to alot of post i have read. There should b someone with a heart to tell me wat my problem is. I dont think there is someone cruel enough to hold onto this infomation as these motors r getting pretty old now. All i need is someone tell me wat to fo and i can fix it as i do have all thr necessary tools to fix.