I run a Yamaha 30 HP 2 stroke (3 cyl) 1985. The boat is an open 4.35 m, 400 kg w relatively flat bottom (easy to plan).
I have cleaned the carburators, disasmebeled the jets (main jet and pilot), the float and needle. Change to new sparkplugs. Changed to fresh fuel. Changed to fresh oil (separaste oil injection).
Change oil in the lower gear case.
I checked the linkage and timining positions (not with strobe light).
Set the pilot screws, the engine idle well and can actually run with the pilot closed, but I sat the to the closest setting in the shop guide (1/1, 1 1/2, 3/4).
The only place I could actually find som debris was in the pilot jets, the holes were clogged.
The engine starts fine, idels stable.
In mid speed the boats runs fine, nice stable and quite.
Compression is fine, even between the three cylinders.
When I give full thrust the stern digs down (I tried differenbt tilt position, no change) and the engines sounds as it is missing power, it doesn't rev up. With one person in the front and my self half way to front reaching for the stering wheel the boat slowly get up to plan. Once planning the engine rev up.
It is impossible to get into plan with only one person in the boat.
What can I do more? are there more jets or narrow holes to clean (brass inserts)?
im not good at yamahas they are a pain in the rump. but id check your points, they might be off they should be able 18thou of an inch at full open position top of a cigerette package folded in half, if it fits in snugly they are fine. first thougth was your losing compression but you tested that so im guessing it maybe the points