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Replaced the factory prop with a new SS prop at 100 hours. The engine dropped 50 to 75 RPM at forward idle and now has a gear raddle in lower unit which goes away when RPM is increased. The tech that installed the prop says it is normal due to the bigger "bite" of the new prop. Would a simple increase in idle RPM correct or is there more to worry about?
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sounds like water chatter,prop sucking air down, not your motor/lower unit. -
The larger diameter SS props can cause a drive shaft noise that is more noticeable in quieter four stroke engines. It will not cause any damage but is annoying. The idle speed for the F115 is 650-750 rpm's in gear keeping the idle between 700 and 750 will help.Comment
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I also have the chatter. I have a 1996 C150 with a 14.25"x19 michigan raptor prop( w/ removeable hub). What prop can I put on my boat that will quiet this thing?
It makes a intermittent clunkity - clunkity - clunk noise at idle , in gear, less than 1000 rpm's
I have checked the following items so far:
timing
cable adjustments
idle speed
low speed mixture adj.
carb sync
complete lowerunit tear down insp. and reassemble
No resolve as of yet.
I dont have the owners manual does it specify a certain prop brand, material, size, etc...? I have never had the stock prop. please help
AdamComment
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Aluminum prop works the best to stop noise. The idle speed on C150 is 575 rpm in gear you can raise it to 600 rpm in gear to see if helps. also when replacing the water pump impeller check that plastic collar and wave washer that are on top of impeller(they are there to help stop that noise), when installing impeller pull upwards on drive shaft and push down on impeller and install plastic and metal collar while pulling up on drive shaft. That helps hold drive shaft up and take some of the up and down motion out of it.Comment
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