Engine Knocking 4000 RPM
08-05-2015, 11:30 PM
#1
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Thread Starter
Engine Knocking 4000 RPM
ok so I know this question has been asked before but I couldn't fine a post where they came back and said what it ended up being so I thought I ask again. so I have a 509 that was just built back in march it has dyno time and maybe 4 or 5 hours of run time. first time out the carb 1100 cfm ended up being to big with the lack of air in my engine compartment ran way rich. changed to 850 carb changed oil and spark plugs. it set for awhile then I took it out and started to here a knocking sound around 4000 RPM it made the sound a few time then when away and ran fine the rest of the weekend. about set for about a month took it back out two weeks ago and heard the noise again around 4000 rpm. oil still looks clean and stay at 75 to 80 psi and about 210 temp. any thoughts.
08-06-2015, 01:40 AM
#2
Charter Member # 55
Charter Member
No way to even guess without hearing it.
Secondly, no decent engine builder would use an 1100cfm carb on a 509 marine engine.
I can't even believe ran right on a dyno.
Secondly, no decent engine builder would use an 1100cfm carb on a 509 marine engine.
I can't even believe ran right on a dyno.
08-06-2015, 01:50 AM
#3
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Thread Starter
I thought the same thing but it had Perfect afrs on dyno made 590 hp and 630 tq. Noise didn't start till after I put the 850 carb on I so I thought made it was a bit lean I change my jets from 82 to 84 and 94 to 96 have had a chance to run it yet.
08-06-2015, 07:01 AM
#5
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08-06-2015, 07:03 AM
#6
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he has a pretty stout motor.
08-06-2015, 07:13 AM
#7
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iTrader: (3)
Probably leaned it down now to the point its spark knocking , and good chance it damaged some ring lands, pistons, or rod bearings.
What is the list number on this 850 you installed ? Was it brand new ? Typically going to a smaller carb , will make the engine richer with all things equal. The dominators moved lots of air, but needed big jets due to booster signal.
Imo throwing a smaller carb on because it was "rich" , wasnt the proper fix.
What is the list number on this 850 you installed ? Was it brand new ? Typically going to a smaller carb , will make the engine richer with all things equal. The dominators moved lots of air, but needed big jets due to booster signal.
Imo throwing a smaller carb on because it was "rich" , wasnt the proper fix.
08-06-2015, 07:31 AM
#8
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iTrader: (1)
ok so I know this question has been asked before but I couldn't fine a post where they came back and said what it ended up being so I thought I ask again. so I have a 509 that was just built back in march it has dyno time and maybe 4 or 5 hours of run time. first time out the carb 1100 cfm ended up being to big with the lack of air in my engine compartment ran way rich. changed to 850 carb changed oil and spark plugs. it set for awhile then I took it out and started to here a knocking sound around 4000 RPM it made the sound a few time then when away and ran fine the rest of the weekend. about set for about a month took it back out two weeks ago and heard the noise again around 4000 rpm. oil still looks clean and stay at 75 to 80 psi and about 210 temp. any thoughts.
08-06-2015, 08:25 AM
#9
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iTrader: (1)
Search function can help when the OP is loosely throwing around terms/parts used.
In reference to the 509, http://www.offshoreonly.com/forums/g...ml#post4259585
quoted below:
In reference to the 509, http://www.offshoreonly.com/forums/g...ml#post4259585
quoted below:
08-06-2015, 08:32 AM
#10
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iTrader: (1)
His last motor was replaced due to knocking also:
http://www.offshoreonly.com/forums/s...ml#post4152891
So maybe a rigging issue ? (fuel supply, exhaust, or etc ?)
Or tuning issues ?
Or engine assembly mistakes ?
http://www.offshoreonly.com/forums/s...ml#post4152891
So maybe a rigging issue ? (fuel supply, exhaust, or etc ?)
Or tuning issues ?
Or engine assembly mistakes ?
