Johnson 150 Stalls At 2800 Rpm?

[Hot Rod]

I have a 2004 Johnson 150.  I just completed an off-season carb rebuild w/ OEM carb repair kits and new carb bowls in an effort to solve some hard to start and rough idling issues.   (Last fall one bowl was warped so bad the float stuck and I took it in to the shop.  Mechanic repaired it but had to replace it with another used bowl because the part was back order at his shop but it worked to get me back out on the water short term).

 

The rebuild went smooth.  Took it out to the lake for a test.   It fired right up and idles as good as new.  The problem comes when I try to get up on plane.  It has no power to accelerate when the engine is under load.  It starts missing and sputtering at 2000 rpm and completely dies at 2800.  Prior to the carb rebuild it ran great at mid to higher RPM so I believe it has to do with the carb rebuild.

 

My initial thought is that it is an air leak or a vaccum leak.  To R/R  all of the gaskets with the kit I had to remove the throttle body and fuel rail (fuel manifold).  I didn't have a replacement for the gasket b/n the throttle body and intake, nor did I have the o-rings for the fuel rail so I just used the old.   

 

My assumption is that this is where the problem lies.  That it is sucking air around the old gasket and or o rings once the engine builds RPM's.  I have since ordered replacements and am hoping that by R/R that gasket and O-rings that will solve it.

 

Anyone have any experience with similar?

[Way2slow]

My first quess is you left something loose in the linkage, like the cam roller or something and it's mainly running on timing advance a very little throttle opening. My first check would be to pull the air silencer front off so you can see the butterflies in the carbs. Go full throttle with the lever/hotfoot and make sure the butterflies fully open and don't over travel. Also make sure all six star to open at the same time. Also make sure the cam roller is at the mark on the cam when they star to open.

Normally, vacuum leks won't let it idle wrth a darn.

Next guess is you have the low speed jets in too far and it's leaning out. I'm not where I can look it up, but I think they are suppose to be at 5 1/2 turns of the seat. Actually that's for a 200, not sure what the 150 sets at, but you might want to find out, because it's not going to run if they are in to far. If nothing else, turn them out a turn and try it, after a few times of this you should be able to gain rpm if they are the problem. That is if your year model had adjustable low speed jets.

From there I would question the float level.

[Hot Rod]

Thanks Way2slow!  Great info.

 

I'm pretty sure the butterflies sync but I will recheck the linkage and the roller.  

 

I never thought of it until you pointed it out it but I bet I've got one or two of the floats out of adjustment.  I thought I checked them all when I reassembled it but I remember having some issues with one in particular and that is probably the exact moment during the rebuild when my wife came into the garage to ask me an "important" question.   I lost track of what I was doing and most likely forgot to check the float alignment before putting that bowl back on.

 

I'll check the floats and see if that eliminates the problem.  Could just one float out of adjustment be the cause?

 

Thanks again!