Going on weight / power/ planning hull..
Guess boat/ motor would be about 400kg add gear/bins and 2 ppl say, 85 kg each that gets to around 600/650kg.
Drop 30 hp on the back
That should give you a WoT around 25mph on paper..
What is your WoT speed?
Problem 1 could be just at min power, another 10/15hp would make a huge difference.
The manual trim pin is either too low or too high. I've got it on the
best position but does not pull the bow nose down to level boat and
plane across the water so I'm thinking it needs more acceleration.
When taking off, one trims right down which makes climbing up over the bow wave onto the plan very easy
.
Then one trims up
for that rpms/ speed..just before any ventilation and/or bow porpoising. The boat increases in speed a few mph/rpms
Manual trim you do not have that option so everything becomes a big compromise.
If want a quick, up on the plain, you set trim down.. and once on the plan will go thru chop better...
Down side, chew thru more fuel, have slower WoT and cruise speeds
... and if fussy, maybe a slightly different prop
If want a good cruise speed.. you will loose holeshot, (climbing over the bow wave as efficient). To establish this trim is a bit of getting familiar with the rig. Normal use boat weight.. try different trim settings at comfortable rpms, trimming up till bow starts to bounce and/or hear ventilation at the prop..and go next setting down.
When I put it into gear it the throttle the stick only engages almost 3/4 forward but it maybe more.
This I am not familiar with your engine or cabling...at all.
If was me..engine not running, I would remove the cowl and move the throttle by the controls (2nd person?) and watch the throttle lever on the carb.. once at WoT does the carb throttle arm go right to the throttle stop on the lever?
If it does you have full open throttle
If doesnt there are usually adjusting screws and lock nuts on the outer cable casing somewhere..usually under the cowl.
You may also find inside the control unit, needs a damn good clean and re grease/lube.. ther maybe also adjustment in there for the lever...Again Im not familiar with your unit, thu think would be very similar to jonnies and evinrudes
Imports thu.. Use a quality brand name grease.. merc / evinrude etc..costs more but hugely better quality in salt water conditions.
And while at it , remove steering cables and re lube those as well..