Johnson Looper V4

[JackHass]

Hello,

What would be the correct factory setting jet (orifice) sizes for a 1991 Johnson V4 looper engine (idle, intermediate, high)? Also, can someone please explain why there are different sized jet (orifice) sizes on the port and starboard side?

I’m at sea level elevation.

Thanks!
JH

 

[racerone]

Do you have a model #-----Is this a 120 / 140 HP 90 degree motor?

 

[JackHass]

Do you have a model #-----Is this a 120 / 140 HP 90 degree motor?

Sure thing! It is a VJ140TXEID. 140HP 90deg

 

[racerone]

Carburetors on one side feed the cylinders on the opposite side.----idle air port is #34 and starboard is #37.-----

 

[JackHass]

Carburetors on one side feed the cylinders on the opposite side.----idle air port is #34 and starboard is #37.-----

Cool! Thank you! What would the intermediate air bleed size be? Are all 4 intermediate bleeds all the same or different between port and starboard?

 

[racerone]

What is your motor doing / not doing ?-----There is very little that can go wrong with these simple carburetors.----Other than plastic carburetor bowl warping.

 

[JackHass]

What is your motor doing / not doing ?-----There is very little that can go wrong with these simple carburetors.----Other than plastic carburetor bowl warping.

Boat sat for a long time. Drained the gas from the tank, cleaned the carbs, and did the link/sync. Right now the boat will idle for about 5 min or so, then it shuts down. Out on the water I can get up on plane at wot I get 5000 rpm initially, then the rpms decrease to 4500 and stay there at wot. At the dock in neutral (no load) I can get up to 6000rpm. The boat is an 18’ center console, about 1900lbs not including the motor. I’m only getting like 20-23mph out on the water.

Attached is a drawing of the jet sizes currently in the carbs.

 

[racerone]

Running a motor at 6000 RPM in neutral is a big mistake !-----Need to determine condition of this motor.----Compression test.----Post your numbers.------Or find shop with a dynamometer to see if motor is developing rated power.

 

[tphoyt]

I have seen rods punch through a block more than once from high rpm’s with no load.
Picture your self running down hill at 60 mph.
You can’t keep it together

 

[JackHass]

Running a motor at 6000 RPM in neutral is a big mistake !-----Need to determine condition of this motor.----Compression test.----Post your numbers.------Or find shop with a dynamometer to see if motor is developing rated power.

Agreed, but it was for 2 sec to see if I can make the rpm. Compression on all cyl is 118-120. New coils, wires and plugs were installed as well.

 

[racerone]

Check flywheel key.----Look into issues with crankcase compression.-----Running with tested VRO or mixing at 50:1 in the fuel tank?

 

[JackHass]

Check flywheel key.----Look into issues with crankcase compression.-----Running with tested VRO or mixing at 50:1 in the fuel tank?

Running with VRO, and I just installed an entire brand new VRO pump.

Idle timing advance I have set to 8 deg atdc
Max spark advance I have set to 18 deg btdc using the Reeves method.
Haven't had a chance to take it out to check wot with a timing light.

 

[JackHass]

Here is a video clip of the problem I’m having at WOT. I put in larger sized main jets (64d). The starboard side has #27 mid and #37 idle. The port has #27 mid and #34 idle. I can get the boat on plane and it will now get slightly past 5000 rpm’s, but after a few seconds the rpm drops off. If I push in on the choke the rpm’s will increase. I’m still trying to figure out if I have a fuel delivery problem or am I dropping a cylinder due to an electrical issue.
View attachment IMG_0031.MOV

 

[JackHass]

Here is a video clip of the problem I’m having at WOT. I put in larger sized main jets (64d). The starboard side has #27 mid and #37 idle. The port has #27 mid and #34 idle. I can get the boat on plane and it will now get slightly past 5000 rpm’s, but after a few seconds the rpm drops off. If I push in on the choke the rpm’s will increase. I’m still trying to figure out if I have a fuel delivery problem or am I dropping a cylinder due to an electrica

Here is a video clip of the problem I’m having at WOT. I put in larger sized main jets (64d). The starboard side has #27 mid and #37 idle. The port has #27 mid and #34 idle. I can get the boat on plane and it will now get slightly past 5000 rpm’s, but after a few seconds the rpm drops off. If I push in on the choke the rpm’s will increase. I’m still trying to figure out if I have a fuel delivery problem or am I dropping a cylinder due to an electrical issue.

Today I ran it off an external tank, and had the same problem

 

[racerone]

If using the electric primer valve improves operation it points to a carburetion / fuel issue.----------Stop running this motor until you find the problem.----A blockage in a carburetor will starve fuel and OIL to one cylinder.----Can cost big $$$ repairs.