Evening folks. 
My 2001 25hp merc is having some issues with running. Once it's up and going all good and it's happy to zoom around all day, but getting there is the issue.

backstory:

hasn't run for 12 months and then nearly 12 months before then.

Got it serviced 15th Jan prior to a trip south. Carby was cooked but recovered. Fuel tank had been empty and I made up new fuel for it before service.

took it for a run before we went south and it started fine, ran fine for the first 10 minutes then as we slowed down to drop some crab nets, it wouldn't accelerate again and stalled. Started again, stalled again as it went into gear. Repay again. 
finally got it going after massaging it through the stall point and it worked fine other than loosing reverse....

down south, it took a bit to get going and stalled a lot at low revs. But once it gets going it's fine.

Three trips out down south with the same. Once it's in gear it stalls, but once you get it past that point, it zooms around no issue.

today, reverse has disappeared again. Stalled as I putted away from the ramp but got going again to garden island where it started playing up hard. Turned out to be the fuel hose which I replaced. See other thread for the story on that one.

anyhow, on the way home, it continued to stall once in gear but I discovered that the fuel bulb is going soft at the point in which it stalls but if I vigorously pump the bulb, I can get it past that point without any dip in revs. 
 

we got back from GI at 15-20 knots and stalled as I approached the jetty and went to accelerate from idle.

the motor is one of those ones that you cannot rev unless it's in gear without lifting the cowling. When I do that, it backfires and stalls.

Out of the water, when in gear, it doesn't stall. I can take it right through the rev range without issue (sorry neighbours).

So fuel hose is new and bulb stays hard

fuel is new

spark plugs are new

connections to fuel tank and motor seem tight

carby copped $150 of service 20 days ago. $850 in total! More than my 250hp! 

any ideas?