Johnson 150 VRO lack of power WOT

[Jayzimmerman3]

Hi all,

These forums have been an AMAZING wealth of information, and I want to begin by saying thank you!

I have a 1987? Johnson 150 VRO (on a 96 Maxum 1800XR, yes I am a little overpowered) that i got a decent deal on and repowered my boat. in the beginning, the motor didnt run (came to find it was the fuel pump, the housing was cracked and pulse wasn't working to pump under load). After a bit of research, i replaced the VRO pump with 2 "premix" fuel pumps from the older non VRO models (old motor was a premix anyway so I had a ton of premix in the boat already).. After some work, got it running and in the water. I am having a few different issues right now:

1. I can't get the engine RPM's at WOT over 4K, even with no one else in the boat. I got to around 4700 when i flipped the choke solenoid to the perpendicular position to allow it to bypass the carbs. I have cleaned these carbs 3 times THOROUGHLY, and rebuilt with new gaskets, float needle and seat, etc. I've linked n synced per service manual's recommendations twice. compression on all cylinders is right around 88-95 psi. This one, by far, is boggling my mind because everything screams fuel starvation, but everything is pretty much brand new (fuel lines included). Not sure if i am missing something stupid here?
2. unless i hold in the choke a bit (with key), the engine dies when opening up the throttle. To the point above, once i get into about 3500, i can take the choke off and it hold 3500-4000 okay. can't get up to the 4500 and beyond range without holding the key in for choke.
3. The thing is a total pain with docking. i can't easily shift out of forward into neutral or reverse. It is okay to shift from reverse into neutral. I noticed it is harder when i am coming off WOT/plane. I usally have to shut the engine off and coast into the dock/trailer. I suspect this is a shift linkage issue, and may just need adjusted?

I've tried to follow most of the advice laid out in the forums here, but have spent a ton of time and don't want to begin jumping into throwing more costly parts at it. Any advice?

 

[ct1762@gmail.com]

motor is most certainly running lean! suspect carbs. did you remove the core plugs? take out the high speed jets and let us know what size they are. sometimes people play around with them, or maybe it was jetted for high altitude. are the throttle plates horizontal when they are wide open? theres a roll-pin on the throttle butterfly shaft that must be strait up when throttle is maxed. insert a toothpick to make it easier to see then adjust wide open throttle stop screw accordingly.
is the timer base free and smooth?
there is a shift interrupter switch by the throttle trunion. make sure its getting depressed at the shift points. what size prop is on the motor?

 

[racerone]

Post pictures or the model # of this motor.-----I do not believe there is a shift interrupt switch on an 87 model 150 here.-----The primer valve puts fuel into the motor.----This fuel bypasses the metering circuits.---This would suggest carburetor issues.------But I do not like your compression values unless it has low compression head gaskets.-----Remove a bypass cover to look at piston and rings on lowest compression cylinder.----And last , do you have spark on all leads that jumps a gap of 3/8" ( 1 cm ) or more on all leads.----These motor sound OK to the untrained ear on 5 of 6 cylinders !-----Check the flywheel key too.------This motor should be easy to trouble shoot.