1986 90 hp v4 evinrude dies when put in gear

i have 1986 evinrude 90hp, it sat up for 2 years. i recently rebuilt both crabs, replaced all the fuel lines, put a new fuel pump (non VRO) and replaced all 4 spark plugs and wires. the engine runs while in neatural, and when hooked up to the hose in gear. i put it on the lake and when i put it in gear it dies right away. any ideas???

Is the idle speed set correctly, if it is to low when you put it in the water because of backpressure it will stall when put in gear.
Is it firing on all cylinders? It will idle great on muffs, but when you put it in the water it will not idle properly.

My first thought is to check your plug wires.
It sounds if you have them crossed.
It will run fine on the muffs and including in gear.
Problem comes in when you apply back pressure to the exhuast
It will idle just fine until you put a load on it as in putting it into gear.
Just my .02

thank you for your feedback. the idle speed it around 600-700 rpms in the water. it let me go into gear a couple times but when i gave it more throttle it bogged down and died. it idles in natural while in the water pretty well. when i got the motor it had a cross threaded plug. but seems to be in there all the way.

Idle speed should be about 750-800 IN gear, boat moving freely.
After removing/cleaning carbs, did you do a proper synch of the link system?

What is the proper sync for the carbs.

I would also do a compression check and a spark check. compression for that motor should be somewhere about 100psi (I think I have the specifics if you need) and the compression on all the cylinders should be within 10% of each other. you noted a possibly cross threaded spark plug hole....if it's bad i would think the compression may be low on that cylinder...if so that would probably give you fits as you're describing. Also run a spark test and that will give you a clue whether you have a plug, or a coil, or a wire or even a power pack that might be going bad. it is possible to get a good spark on all cyls while on the muffs but then not so good when in the water - but at least having a good spark all around while on the muffs is a good start.