1985 & 1987 JS 550 Issues w/ running in water

[Oakley1234]

I have a 1985 and 1987 JS 550. Both are in good shape, great compression, and just changed out both carbs to the SBN 44's. They both fire up and run great out of the water (they'll rev up and idle), but when they enter the water, its like the throttle doesn't exist. I'll pull the throttle all the way back and it wont come out of idle, and sometimes it'll die. They're stock except for the carbs.

Carbs were put on my mechanic with plenty of experience. He said they're jetted correctly, ran fuel lines straight from tank to carb, and cleaned before installing.

Have proper oil/gas mix in tanks as well. Brand new battery too.

Any ideas? Any help would be great. I'm also new to the hobby, so if you could ELI5 (explain like I'm 5), that would be great. This is the only pic I have right now, but can easily get more.
Thanks for the help!

 

[kswiatk]

If both aren't working, then i wouldn't be so sure of the mechanics jetting. How can he be sure of it, if he only ran them out of water?
Start by checking for the jet numbers on the carbs, as well as the pop off, it'll probably too high.

 

[Oakley1234]

Ya I thought it was a little odd both of them are doing the exact same thing. I just took his word for it. He's going to take them out to the lake and see if he can't figure out whats wrong. But thats in a week, so I was hoping to try and mess with it first.

What should I be checking for on the jets and the pop off? Do I need to have it in the water to do this? Could it just be a tuning issue?

Also, here's another picture of engine.

 

[Gottadog]

Ya I thought it was a little odd both of them are doing the exact same thing. I just took his word for it. He's going to take them out to the lake and see if he can't figure out whats wrong. But thats in a week, so I was hoping to try and mess with it first.

What should I be checking for on the jets and the pop off? Do I need to have it in the water to do this? Could it just be a tuning issue?

Also, here's another picture of engine.

You need to open the carbs and see what jets, needle and seat and springs are in the carbs And turn in the low and high adjusters making note how many turns so you can put them back. Then you'll know what you have and at that point people can help you more thoroughly.