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1985 115hp evinrude rough at idle

B

buggle

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I posted months ago regarding my motor and rebuilding it. Well it is rebuilt now by a good local st. Pete Fla mechanic. There was just to much involved for a rookie. I am still breaking it in by the book. I am only at 4 hours into the break in period and still need to bring it by the mechanics. I had the motor completely rebuilt new crank,rods,pistons, and heads. I am having the same problem as Nitrofreak running rough at idle and backfiring. but once I get the RPM's up to 2000 running in gear it smooths out great. I just can't sit in the water and idle. Is this due to the break in period or could it be my carb's too.
 
Firstly, any break-in should be done as quickly as possible.
Take some full days boating and get it over with.
Personally I used to do a 4-hours break in in my test tank running on a dyno before handing to the customer. This to be able to adjust as close as possible.
Check your spark plugs -should have even color.
Check that temp is even at both cyl-banks and 'barely to touch' at idle.
When running at 'idle' are your exhaust relief ports above water?
Contact your re-builder and if possible have him take a test run on the boat at sea.
Testing under real conditions are the only correct way, not in his work shop.
Quite often problems may be related to boat/installation/ tank etc and not engine itself.
 
Haffiman thanks for the reply. I called my re-builder and he said it could be varnish build-up in the carbs. He told me that the motor was most likely running lean due to the air jets being clogged and there is no air ajustment screw on my 115 hp motor. He recommended that I remove the carbs, bring them into him and he will soak them in a tank of solution. Is there a carb cleaner I can use while the carbs are still on the motor so I do not need to remove them.
 
I need to clean my carbs can I use a gas treatment or spray something directly into the carbs to clean the varnish from air jets and needles. I was told by my re-builder to remove the carbs and bring them to him so he can soak them in a solvent. I was just wondering if there is an easier way.
 
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Hello, I am a pretty good small engine mechanic, and I have been working on this 1985 Evinrude 115HP. It now has good fuel, spark on all 4 with a new power pack and 2 new coils. Starts and runs nice with no problems until Idle. The carbs are rebuilt and adjusted properly. It does idle until there is a Poof sound through the exhaust and then it starts to run rough. It keeps doing it until if the Poof sound is too much, it stalls the engine right out. Restarts fine but will not stay running in idle. Now the weird part is this, If I can get it in gear and I have, the poofing sound stops under load and it idles fine but not in neutral. And BTW, the Poofing sound is from the exhaust and blue smoke comes out. Any thoughts? This mototr was bought by a customer sight unseen and I am trying to bring it back to life for them. Thank you anyone.
 
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