Mercury

I have a 1984 75 hp mercury outboard motor, it runs nice when it’s out of the water, but when there is a load behind it, in the water is bogs down and dies. i’ve had the carbs rebuilt, fuel lines replaced, fuel tanks cleaned, filters added, stator replaced and the certified mercury mechanic spent 5 hours trouble shooting saturday and can’t find the problem. does anyone have any suggestions?

Make sure your trigger is advancing your timing all the way. i assume your compression is good (all within ten pounds of each other).it sounds like your synch and link might be off. ask your certified mechanic if he checked all the linkages and timing advance.