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0520 gpu runs backwards on shutdown.

malone

Member
Air boats rule!! I bought my first one last christmas (with no pressure from my buddys) yeah right..Any way its an 0520 gpu gitsu on an 11-10 Rivermaster knock-off. it wants to run backwards on shut-down after cool off. Here is the good part. Delco- Remy 6 cyl distributor and a bendix mag working together. replaced points, cond on dist, havent touched mag. been running fine for months but the last two shutdowns started seeing this. Career "Marine side" boat mechanic,
needs advice.Thanks in advance!
 
Is the idle low..... mine will run backwards if idle is too high... it idles about 650 and shuts down nice.

For others to comment... what carb do you have?

Good lock

AirHog
 
Upstack? As stated above, set idle up a bit, set idle mixture screws till each equally lean out and it starts to stall, open each back up 1/4 Turn or till it just starts to lope, back idle down to 600-50 rpm.
 
I found a cracked vacuum cap on the throttle plate. Replaced, and it went back to normal idle. Test when the rain goes away. My tach is bad and i didnt notice the gain. That was a new cap I put on 4 months ago. I made my own out of marine fuel line scrap I Had this time. Thanks for the input, got me pointed right !
 
If you have access to a lathe or a good machinist, have an aluminum plug turned to peen into the port once pulling out the steel barb, do the same with the vacuum advance port with a 3/16 rivet, no more rubber caps needed.
 
Lean = hot cylinders which will ignite fuel without spark(run on). Check the overall tune as its prob on the edge and not in the happy spot.
 
While it was raining nonstop I opened up the mag found water in the rotor side vent plug was stripped. Fixed that timed the mag to the distributor. Got to run it today from Lake Laughlin up to 46 round trip. She shut down nice and pretty. Thanks for the input. We both found our happy spot today..
 
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