Logo
FULL SITE MENU

1993 Johnson 115 VJ115TLETS locking up. HELP

N

ngraham

New member
I have a 93 Johnson 115 cross flow. Recently the only way it would run is if I bumped the “choke”. I pulled the carbs and cleaned them, replaced the gaskets and needle and seat. Did a link and sync, joe reeves method WOT timing and now if I run 4000 + rpm’s for a short time, the engine locks up. No high temp alarm but engine is hot and will not rotate until it
cools. Wait 1 minute and it fires back up. It will run slow speed all day. Any suggestions??? I’m wondering about float height? If the float drop was adjusted too low, could that cause this? Did not do this until after carb work.
 
The engine is experiencing thermal seizure (a cold/lean freeze) at high RPMs because it is running dangerously lean. Since this issue started immediately after the carburetor overhaul, a severe fuel-starvation condition is starving the cylinders of fuel and oil, causing extreme friction, overheating the pistons, and soft-seizing the engine.

Do not run the engine above idle until this is resolved, as repeated thermal seizures will score the cylinder walls and destroy the powerhead.
 
  • The Fix: Remove the outer drain plugs on the carburetor bowls and inspect the main jets. Ensure they are completely clear and screwed in tight.
    • The Fix: Remove the float bowls, flip the carbs upside down, and verify that the floats sit level/parallel with the bowl gasket surface. Check float drop to ensure the float hangs down sufficiently to pull the needle off the seat fully without binding.
 
  • The Fix: Re-torque the carburetor mounting bolts evenly. Check that the new bowl gaskets are seated properly and not pinched.
    • The Fix: Re-verify that you subtracted the standard 4-degree offset correctly during static testing (e.g., if target WOT timing is 20° BTDC, static cranking test should set at 16° BTDC).
    • Ensure the VRO or mechanical fuel pump is maintaining adequate pressure at high RPMs and isn't pulling air through a degraded fuel line connection.
 
Elite Boat Engine said:
The engine is experiencing thermal seizure (a cold/lean freeze) at high RPMs because it is running dangerously lean. Since this issue started immediately after the carburetor overhaul, a severe fuel-starvation condition is starving the cylinders of fuel and oil, causing extreme friction, overheating the pistons, and soft-seizing the engine.

Do not run the engine above idle until this is resolved, as repeated thermal seizures will score the cylinder walls and destroy the powerhead.
Click to expand...
Excellent advice. If the OP's engine is locking up solid with a lean seize I would be very concerned there is already cylinder wall damage.
 
What kind of fuel pressure should I be looking for? Idle vs. wide open? Max pressure drop? I did have to sand down both of the carb bowls due to warpage. My float drop may have been set to too much drop. Motor still starts and idles around good.
 
There is a spot on the intake manifold to mount a simple ( cheaper ) pump.----Look for it just in front of the starter.----Mounts directly over the PRESSURE pulse port with a gasket.----Plug Pulse limiter port.-----One hose for fuel in and a second hose for fuel out,----Find the part# on a 1983 model or on an 88 HP special model.
 
Let's clarify your issue:

*Ran OK until recently then needed choke to keep it running? YES/NO
*You cleaned carbs & it ran better then seized or you shut it off then it wouldn't crank again until it cooled?
*Engine won't crank until it cools and/or the flywheel won't turn even by hand?

Too much float drop will not cause a lean condition, too little can especially at high power settings.
 
correct.
What did confuse me was setting float drop. I believe I may have set it so the float so the float literally dropped 1 1/8 from casting surface to top of the float (so not including float thickness) instead of measuring from casting surface to the bottom of the float (so including float thickness) so now total measurement of float drop from casting to bottom of float including float thickness is 1 inch. Sorry if that confusing….

My jets were almost completely clogged. Everything is clear and clean now. It will start and idle and go up to 2000 no problem…. Before all this I could get 5500 easy. Now 5000 is all it’s got (probably because it’s running lean) and then yes, engine slows down rapidly and locks up. I did my best to do the joe reeves timing method. And I don’t think I have the “quick start”. Honestly, I think I want to delete my vro. I’m going to vacuum/pressure test it this weekend. I’d like to know more about that procedure. Sorry long post. I enjoy learning and tinkering with engine (mostly model T’s). Thanks!!

I would like to check my vro pump.
 
Pump won’t hold pressure. Dunked it and found it blowing bubbles out of this crack…
 

Attachments

  • IMG_6056.jpeg
    IMG_6056.jpeg
    516.8 KB · Views: 6
Back
Top