Check float bowl and carburetor body for signs of warping.-----If it was the only motor I had I would install 3 or 4 wee pins on that surface.-----Just to trap the gasket , prevent it from moving.
Need to understand that idle ---" primary pick up " ----is the point where throttle plates start to OPEN.-----So in fact that has nothing to do with how the engine idles.-----So a " no money " spent procedure is to open low speed mixture screws 1/8th turn at a time till you get smooth acceleration !
Stop.----The wee lines that go into the top of carburetors are for the electric primer valve and have nothing to do with oiling.----No need to touch those small lines or the other wee hoses for the oil recirculation system.-----The oil was mixed with the gas inside the VRO pump.------What pump...
???------There is one wire going to the choke solenoid.----Use a jumper wire and put 12 volts to the solenoid.-----It should click and pull the choke on.---Also make sure that choke is not in the fully on ( manual lever ) position now.
I have a 1980 17' project boat rated for 150 HP by US Coast Guard.----Have a 1997 model 150 HP 2 stroke at about 380 LBS,------New 150 HP 4 stroke is 520 LBS.------- Motors not rated at the prop in 1980.------I do not believe the 4 stroke would be correct !
I do not believe these rules / capacity plates are well thought out these days.-----They have never been adjusted for propshaft power or the increased weight of modern motors !
The ends are similar but not exactly the same.----The end that is NOT broken goes on the tower shaft.---Open end would face you.-----Not hard to figure out the installation I think.
Not all motors are built with the best materials.----An owner can use some tricks / sealers to prevent threads from getting water in them.----That causes corrosion to build up and jams stuff.-----Also there is something called " hydrogen embrittlement on stainless fasteners.
I do not believe that the " 400 " models were electric shift.----Agreed ---Does exhaust come out the center of the prop ?----Is there a shift and throttle cable on that control ?