1997 Johnson 40 Missing Carburetor Mounting Gaskets

T

Tug Captn

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Bought very clean freshwater 1997 Johnson 40 for my 4m Avon Searider this spring and I always thought it had a rough idle. Top end and off-idle seems fine. Last week it stopped idling on one cylinder so I pulled the carbs for a cleaning, did a link & sync and set the timing per the jon reeves method. VRO has been removed and I mix Amsoil HP injector at 50:1. I noticed that there were no mounting gaskets at all between the intake manifold and the carbs which I thought was odd, but it looked as if they had never been off before so I put everything back together the way I found it.

Motor definately runs better, mixture screws repond as they should, top end is good but the idle just seems too rough. Compression is dead on 135 for both. I finally looked at a parts diagram and it does show carburetor mounting gaskets. I ordered the gaskets, but wondered if anyone had run into this? Did OMC elimitate the gaskets at some point? I can't imagine the carb and intake manifold are machined tightly enough not to need it, but I guess it's possible??

I'm assuming that the motor has been running lean from sucking air where the gaskets should be, but the compression is still good so everythig should still be ok? Hoping there has not been any damage from running it this way. I always have had great luck with older OMC stuff


Thanks for any input,

Tim
 
R

Rick.

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Re: 1997 Johnson 40 Missing Carburetor Mounting Gaskets

I would put the gaskets in for sure. I would be surprised if you had a good seal. Did it idle fast? I think it would have if it was leaking. I know my 95 - 40 has them in place. Best of luck. Rick.
 
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Tug Captn

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Re: 1997 Johnson 40 Missing Carburetor Mounting Gaskets

Rick. said:
I would put the gaskets in for sure. I would be surprised if you had a good seal. Did it idle fast? I think it would have if it was leaking. I know my 95 - 40 has them in place. Best of luck. Rick.
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Thanks Rick,

I will put them in for sure...there is no way the carburetor mounting flange is machined that tight. It idled a little high in nutral then would drop WAY down in gear. I can tune it out to keep it from stalling, but always idles rough. I'd never stand for it on a boat that does any trolling, but my inflatable spends a lot of time near WOT...it's just too much fun!

At work on a tugboat not...will post back results when I get home.

Tim
 
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