fred, i assume you did the engines yourself or that the builder didn't have access to a dyno.
from past experiences, stock holley cards are 8-10 jet sizes to big. they do this out of fear running to lean. next you add in that your using it in a marine application where the motor runs at very low engine temp (under 140) and most are running low oil temp (under 180). this makes things worst since the engine itself isn't getting hot and hinders the combustion burn.
in race appications i've run holley and holley HP, barry grant, quick fuel and had to make major changes to all of them while dyno testing. now i know this is expected in some cases but both barry grant and the quick were built supposedly to match up with what we were doing.
after spending $$$ tweaking the carbs that i had, we built another motor and that time around listened to the builder and bought a new carb from BLP.
http://www.blp.com/
since then these are the only people i deal with for carbs. the owner is an old nascar guy and these guys only do carbs.
now you already have stock carbs but outside of jetting theres a bunch of other things that affect its performance. i would give these guys a call and see what they have to say before just changing jets.
and one other thing, just to keep up on stuff i recently read a book about performance carbs, which basically clarified what these guys told me. the actual jet size is a small factor in overall performance of a carb. there is many adjustments and modifications that can be made other than jetting. air bleeds, venturi size, accell pumps, floats, ect, ect.
i run there 850 and 650 race carbs and our motors produce better dyno #'s than most the others i race agianst (spec stock type). plus the carbs have never stumbled or given us trouble.
side note, few yrs back i ran into fuel flow problems. boat kept stalling in the turns. a few other racers/mechanics were helping figure out the problem and decided we should tear down the carb. no problems there. but it was discovered that i was running about 10 jet sizes smaller than everyone else. some of the guys thought this was the problem and recommended changing to bigger. it turned out to be a sticking fuel regulator. i left the carb alone. on our next rebuild i brought this to the attention of my engine builder and asked about changing to a bigger size. as you guys know most guys don't like being questioned about this stuff, but to prove a point we ran several dyno pulls and the overall best performance ended up right back at BLP's original size. whereas on other dyno tests with other carbs we constantly were dropping down 4-8 sizes.
so basically talk to as many people as possible before making any changes and know what your doing before making adjusts.
