carbbed 540 popping through the exhaust

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alumitech520
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carbbed 540 popping through the exhaust

Post by alumitech520 »

motor ran great at first , the started popping through the exhaust from the right bank ( pilots position) then occasionally from the left side. could this be from running pump gas . was told when I got the boat it ran good on pump gas with boost and marvel myst oil. sometimes it would pop more than others. tach isn't working so I cant give an rpm range. it seems to pop from mid range to high range rpms. or could it be from restricted fuel system causing a lean condition? does have a man pump and elect pump it that helps any. need all the advise I can get , I don't want to cause any damage to the engine . thanks guys for all info given.

Dreadneck
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Re: carbbed 540 popping through the exhaust

Post by Dreadneck »

check the plugs

twister69z
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Re: carbbed 540 popping through the exhaust

Post by twister69z »

Compression test first, then the tale will be told.....
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schmidtav2
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Re: carbbed 540 popping through the exhaust

Post by schmidtav2 »

Also look for any leaks at the intake pipes (gasket and hose) and at the exhaust gasket area.

cowtown
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Re: carbbed 540 popping through the exhaust

Post by cowtown »

running lean !!!
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keebo
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Re: carbbed 540 popping through the exhaust

Post by keebo »

as said before leakdown test first, all good answers but could be a mag too. Had it happen on SV carb 540
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alumitech520
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Re: carbbed 540 popping through the exhaust

Post by alumitech520 »

I don't have the proper equip for leakdown test. but comp is as follows cyl 1 170 psi with a med brown plug , cyl 3 170 psi with carbon build up blk plug, cyl 5 170 psi with carbon build up blk plug, cyl 2 175 psi with med brown plug, cyl 4 175 psi with carbon build up blk plug, cyl 6 170 psi with carbon build up blk plug. all top plugs. im not sure how accurate the guage is , I borrowed it from someone else. while doing a little looking around , I checked to see if the throttle was opening all the way I noticed the accel shaft has a fair amount of play in it. tag on the carb says ma4-5 model number 10-3859-1. thanks again for info and advise given .

victorg
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Re: carbbed 540 popping through the exhaust

Post by victorg »

I have a leak down tester you can borrow!

twister69z
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Re: carbbed 540 popping through the exhaust

Post by twister69z »

Isn't Southern Airboat great! People loaning tools for fellow airboaters. Forgot to ask what kind of plugs? Automotive or aircraft? Try a tank of avgas also drain the carburetor bowl check for water.
Twister69z
If you don't have time to do it right the first time ,
Where are you going to get the time to do it a second time?

alumitech520
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Re: carbbed 540 popping through the exhaust

Post by alumitech520 »

autolite 386 , twister does the comp sound right to you? thank you for your help.. vic , I didn't know you had 1 , I would have gotten it the other night. thanks buddy.

loudmouse
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Re: carbbed 540 popping through the exhaust

Post by loudmouse »

I would check the fuel filter, check mag, change plugs, refire and if the pop is still there the carb might have water or trash in it.
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breastquest
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Re: carbbed 540 popping through the exhaust

Post by breastquest »

Run it till it pukes the part out that's causing it to pop!!

twister69z
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Re: carbbed 540 popping through the exhaust

Post by twister69z »

At least they are close together, a differential test is more conclusive but that is coming..
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If you don't have time to do it right the first time ,
Where are you going to get the time to do it a second time?

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