Johnson 150 fast strike starting and acceleration issues

Joined
Jul 28, 2025
Messages
6
Hi all! I have a 1994 Johnson 150 fast strike. On my first run this year, I noticed when taking off my boat would not plane out, it was would only have about half power, just stand straight up but not plane out. I would let off, and punch it and it would take off just fine. It’s now getting worse as I take it out, it’s hard to cold start in the water and on the house, but hardest when submerged in the water. It is now stalling and bogging under acceleration so bad that I can’t even get it off the trailer anymore to try and troubleshoot on the water, and when I finally can get it off the trailer I have noticed that when it bogs on takeoff it stalls, but if I press the key in and activate the primer it picks up and takes off, and I’ve noticed at WOT it does fine for a second and loses some power, and when I again activate the primer with the key it picks back up and comes back to life. I have noticed when trying to cold start it, if I have someone put their hands over a few of the carbs it fires up so much easier. I have been thinking about using clear tubing to look for air bubbles, just haven’t gotten around to it yet. It also runs a little rough, but runs much better on the hose at idle than it does in the water. It almost seems like my problem is intermittent when it comes to cold starting, especially on the hose, some days it fires up on the 3 try, but most days it pops and instantly quits, and I gotta try it over and over again probably 10 times before it’ll fire and stay running. But once warm it hits a lick with the slightest numb of the key. I have also noticed if I prime the bulb and let it idle, it’ll idle for about 20 seconds and then die out, and when I pump the bulb back up its almost completely empty, doesn’t go flat, it’s just SUPER soft. Which leads me to think maybe an air leak somewhere between the motor and tank? I know that would cause the bog and stall, but would that cause such a hard cold start? I’m leaning towards carbs needing rebuild/ cleaned due to hard starting and when I press the key to activate the primer that it momentarily fixes the bog and stall issue. My compression is good, all at 125 and the lowest being 118. Also I tried a portable tank yesterday on the hose and it did not fix the hard starting, will see if maybe it helps with the bog when under a load while on the water this weekend. Also I’m not sure if I mentioned it above, but the bog and stall during acceleration only happens while under a load and in the water, does not bog in gear on the hose. I’m not a mechanic in any way, so I’m not really sure where to start. I also forgot to mention that when in neutral, when I rev it and as the rpms come back down it’ll die most of the time unless I feather the gas to keep it from stalling out. Carb issue? Any help would be greatly appreciated!
 
Joined
Jul 28, 2025
Messages
6
Compression and spark are fine, it does not leak as someone would think of a leak, I also keep my boat stored with the motor in the vertical running position. So I don’t imagine it would leak as I assume the fuel level is below the gasket and flange due to the float? Just my opinion. But I do see seepage of fuel between the gasket (s)
 
Joined
Jul 28, 2025
Messages
6
I’ve thought about using clear tubing for my fuel line, just haven’t done so yet to look for air bubbles. After seeing the seeepage and gaps in the carb bowls I’m hoping that’s my issue, I’ve been told those black gaskets are the original gaskets, if so then those carbs also need rebuilt badly, assuming that’s true, it would mean they haven’t been rebuilt in 20+ years considering this is a 30 year old motor. Can’t understand how I haven’t had more reply’s for suggestions. No offense towards you in any way, just saying the more suggestions I get the more things I can eliminate. Thank you very much for your reply’s, anymore suggestions you have would be GREATLY appreciated buddy!
 
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