2008 4.3 not running

[supersoaker548]

my buddy has a 08 4.3 holly carb . trys to start but hard to get to fire and when we did get it started sounds
like running off 3 cyl. hold open and about 3 - 4 sec. latter rpm jumps up some and a couple more sec. it takes off .. bring to 1/2 throttle sounds great revs good but want idle and wont rev again hold at 1/2 throttle tell rpms jumps up again and runs good 1/2 to full open . cleaned carb but no change . sounds like a timing problem to me .

any and all ides wellcome

 

[alldodge]

Is this a new to to him boat?
Was it running prior and this just started?
What have you done other then just try and crank it over?

I would start with a compression test

 

[Scott Danforth]

in addition to AD's questions

please explain how he cleaned the carb. most people never chase the passages in the idle circuit.

what you are describing sounds like a bad power valve in addition to a dirty idle circuit.

 

[89retta]

Check the cap and rotor

 

[supersoaker548]

he's owned it from new, ran great at end of last year. he never got it started tell I got there . I really thought it was the carb so I got a new holley kit and did the carb. was very clean in side but did soak in carb acid type cleaner then flushed just like I do on all my holley rebuilds . new power valve , new plugs cap rotor . when he gets back to the lake I plan on doing a comp. test and leak down test . Thanks Scott and I have no way to chase the passages