Air Silencer needed? 1980 85hp V4 Johnson

Joined
Apr 7, 2012
Messages
2
I have recently re-powered my 1966 Mark Twain V-Sonic from the original Merc 90hp "Tower of Power" with a 1980 85hp V4 Johnson, model #J85TLCSA - I have been working on getting everything running tip-top and starting to make improvements but still seems to run a little rough and will simply cut out after idling for a few mins at a time I can "get by" a day on the lake but it doesn't run right (or consistent) and every time I restart it I have to choke it to get it to fire. At WOT it is pushing my fairly heavy 16' ft runabout at 32-35 mph.

I decided to dive into the process of removing and throughly cleaning the carbs - when I looked at the repair manual I noticed that my outboard does not have the "Air Silencer" attached at all. After looking into it for awhile I have found very little about whether the Air Silencer is necessary or not - and even less luck on finding a replacement.

My 4 questions are:
1) Is the Air Silencer necessary?
2) Does it radically reduce the noise of the outboard running?
3) Does anyone know where I can find a replacement?
4) Based on what I described above, any suggestions on improving how my Johnson is running?

- Thank you -
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: Air Silencer needed? 1980 85hp V4 Johnson

It is possible that your running issues are carb related. If the new engine was not properly winterized at the end of last season, the carbs could have some dried fuel residue inside the fuel passages-restricting fuel flow. New fuel just won't dissolve the old, dried up fuel. You need to tear the carbs down and use a carb cleaner product which will dissolve old fuel tar, like the aerosol product: Gumout. Likely the engine will run (idle) much better. The factory will tell you that the engine will run slightly leaner without the airbox (silencer.) Generally not a good idea to run "leaner" long term. That's the factory positon. The thing is that these early engines seem to run with plenty of fuel in the mixture and some folks claim long service without one. I always run one-most folks do. I wouldn't say noise an issue one way or the other. Likely the airbox cover is NLA, but there were many thousands of these made and you should be able to find a used on most anywhere-even ebay. Regarding running improvements: These engines are suseptible to carbon accumulation around the ringsets. Since this engine is new to you, I'd suggest running a can of Bombardier Engine Tuner through the powerhead. This carbon cleaner will remove carbon around the rings, may improve compression a few lbs and maybe even improve the idling characteristics. Not expensive-it's a good preventative maint item.
 
Joined
Apr 7, 2012
Messages
2
Re: Air Silencer needed? 1980 85hp V4 Johnson

@emdsapmgr - Thank you your for the advice, I will get into the carbs on Friday and see if that makes an improvement. I will also look in to that powerhead tune up you suggested. I will post results this weekend.
 
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