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High Speed Jets Looper 150

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ohana

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I have a 2001 Johnson 150 looper that I can not get to reach past 3500 rpms and was told by a dealer that inspected the motor that the high speed jets were enlarged by years of ethanol fuel and were allowing too much fuel to pass through the carbs (I also noticed that at 3500 rpms the floscan showed 17 gallons per hour, where as at 3000 rpms, floscan showed 8 gallons per hour..with only a 5 mph increase in speed).

First, is it possible for larger high speed jets to cause a motor to not reach max rpms and second, has anyone ever heard of ethanol causing this condition?
Thanks
 
I assume the jets in the carb are brass, is that correct? I've never heard of ethanol 'eating away' at brass and causing it to enlarge. The only real effect I've seen as a result of ethanol fuels is maybe some corrosion and/or gumming on aluminum components and swelling/degradation of rubber hoses and o-rings that weren't designed for ethanol exposure. However, your motor is new enough that it should have been engineered for ethanol based fuels and I wouldn't think you'd see catastrophic results using those fuels. Engines from pre-1990 (and maybe into the early 90's?) weren't engineered with ethanol in mind so there can be issues with rubber and diaphragm degradation. My jet skis are 1994 and 1996 models and the manual for both require 87 octane for non-ethanol fuel and 89 octane for ethanol fuel. If Polaris was onto ethanol containing fuels I would bet the entire boating industry was as well and were making engines ethanol compliant.

If you're not the 1st owner of this motor, it's possible a previous owner over-sized the jets trying to improve performance in some way. An easy check is to run the engine at WOT then shut down quickly. As soon as possible remove one or more spark plugs and inspect them. If they are wet it is possible you are over fueling the motor, but it can also mean you have weak spark.

KJ
 
The high speed jets (1 to a carb) are located in the bottom center portion of the carburetor float chambers... way in back of that brass drain screw plug. They are installed via a 1/4-20 thread with a regular screwdriver slot BUT that slot is wide and flat (see below). find a screwdriver with a shank that will fit perfectly within the plastic threads of the float chamber, cut off the thin tip and file a new tip to resemble the one you see here.

On the side of the jet will be a number indicating the inside diameter... what is that number? Phone your dealership and ask what size the high speed jets on your engine are supposed to be... SO NOT tell him what you see on the jet until he answers your question!

317002a_CARB-JET_REM-INST.jpg
 
ohana said:
I have a 2001 Johnson 150 looper that I can not get to reach past 3500 rpms and was told by a dealer that inspected the motor that the high speed jets were enlarged by years of ethanol fuel and were allowing too much fuel to pass through the carbs (I also noticed that at 3500 rpms the floscan showed 17 gallons per hour, where as at 3000 rpms, floscan showed 8 gallons per hour..with only a 5 mph increase in speed).

First, is it possible for larger high speed jets to cause a motor to not reach max rpms and second, has anyone ever heard of ethanol causing this condition?
Thanks
Click to expand...

Go to the top of the page, order yourself a printed manual for your motor, then fire that "mechanic". Sounds to me like he's "fishing" to see how gullible you are.

You made no mention of fuel line, primer bulb, filter cleaning/replacement. What are the age/condition of them?

Wanna see the inside of some of the line people buy from SprawlMart? That's just one end, imagine an entire fuel line in that condition.

 
Bovine Scatology !!!! Yes jets do wear over the years but only about half a size larger and would not richen it up enough to keep it at 3500.
 
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