1989 48 HP Johnson Outboard No WOT With Air Silencer On?

[Highdog1]

Hi - Gotta problem with my boat motor and I can't seem to figure this one out. With the air silencer off the motor runs great as it would run normally. I take the air silencer off, it just bogs down and won't go wide open. I've got good compression and spark. I've also checked the electric primer solenoid (thinking it was getting too much fuel in carbs), it seems fine. Also rebuilt the carbs and fuel hoses to the carbs. Fuel pump seems to be pumping fine. Would really appreciate some help! Thanks.

 

[juno pierrat]

re-read your post, you say silencer is off twice

 

[Highdog1]

Yes, I sure did. What I meant to say is with silencer on it bogs down and won't go full speed. When I take the silencer off , it opens up a goes full throttle.
Thanks juno pierrat for catching that.

 

[jakedaawg]

Silencer full of mudaubers or mice?

Are you putting it on upside down somehow and interfering with linkage? (Doubt it's possible but...)

Is the air opening in the lid the issue or are both of these without the lid on.

Excessive smoke getting into Silencer?

Just a few thoughts...its probably something stupid simple.

 

[juno pierrat]

the gasket between the carb and silencer, can it be backwards,

 

[Highdog1]

jakedawwg - I did check all that out, silencer cover goes on only one way. I've not seen or noticed any smoke/exhaust coming out of under cowl or carbs.
Thanks.

 

[Highdog1]

Juno pierrat - actually the more I was checking out that gasket , it was on the right way, but it's looking pretty worn and had gas on it ? I ordered a new one and a reed box gasket too. Is that normal for that gasket to have gas all over it?
Thanks.

 

[Highdog1]

What I've also been pondering on is an exhaust leak somewhere? But it idles good , slow speed is perfect with silencer on, it's just wide open it will bog with silencer on. With it off, goes great doesn't miss a beat on wide open. It just wants that damn silencer off lol.

 

[jbuote]

Granted, I very new to outboards, but it does sound like it's starving for air and running too rich at WOT..
​I'd have to ask the same as jakedaawg did:

Is the air opening in the lid the issue or are both of these without the lid on.

​Were both your tests with air silencer cover done with Cowl/hood/lid on or off?
​Could the air inlets on that be blocked?
​Didn't see that answered, so I apologize if I missed it..

​For whatever that might be worth from an outboard newbie.. lol

 

[Highdog1]

jbuote - I did check the air inlets and they are fine. That was my initial thought was too much gas in the carbs. So I rebuilt the carbs, put new fuel hoses , and checked to make sure the primer solenoid was coming on and off as should be. Also checked the fuel pump. I really don't know any other way i could be getting too much fuel? the high speed jets are coming on when should and both working. But more fuel would explain needs more air , but still no success on that front.
Thanks for your response.

 

[Highdog1]

jbuote - oh forgot! Yes, I tried with just cowl no silencer and opened up. With silencer on no cowl same problem , won't open up just bogs.

 

[jbuote]

Yeah.. I was just thinking not so much that you're getting too much fuel, but rather not enough air...
​Meaning it might be set up right with the proper amount of fuel, but the air is restricted somehow, with the silencer on, at WOT which creates the rich condition.

​Anyway, that was my thought..
​I leave it to the more experienced folks here to advise further..

​Thanks for indulging a newbie for a minute! lol :joyous:

 

[Highdog1]

jbuote - that makes sense . I've been so focused on the fuel , not an air restriction. Then runs rich, bogs it down. Im not sure where air getting restricted at this point.
Hey, no problem. Thanks for the input! Your suggestion is a good one. I've been chasing my tail so to speak on the fuel.

 

[jakedaawg]

jbuote - that makes sense . I've been so focused on the fuel , not an air restriction. Then runs rich, bogs it down. Im not sure where air getting restricted at this point.
Hey, no problem. Thanks for the input! Your suggestion is a good one. I've been chasing my tail so to speak on the fuel.

this IS an air issue, probably simple. May be air quality, but surely air availability. Or a linkage interference

 

[juno pierrat]

the silencer is two half's, attach first half, and ruin it. any difference. also on my 87' theirs a vent tube at the bottom of the silencer to the crank case, maybe its got something to do with it. try with on and off
and yes my old gasket was gas soaked when changed, it seemed to run better but that was several years ago, may just be brain fade

 

[Highdog1]

jakedaawg - sure sounds like it's right in that carb/manifold area, I've ordered new gaskets for around the reeds and manifold and carbs. The linkage is good, its moving freely and advancing. Hope its simple lol, thanks.

 

[Highdog1]

juno pierrat - I've not tried that and will do. I have checked that vacuum hose but just the hose itself, not the actual fitting ends that the hose connects to on both ends. Maybe one of the fittings is gummed or plugged. As noted above, I've ordered those gaskets and will do as you suggest and see how goes. If there's anything else I should be looking for or place to look please advise. Glad to know it doesn't seem fuel related.
Thanks.

 

[jimmbo]

Are there any air bleeds/vents on the carb body that are getting blocked by the gasket or air box? Does the air box impinge on the cold start enrichment system in any way?

 

[Highdog1]

jimmbo - they do have air bleeds at the top of them but the cover to the box protrudes out far enough it appears no blockage there. The primer solenoid is located behind the silencer. Really frustrating! Im debating if I need to tear it down more and be looking in the exhaust somewhere. But i would think I'd see at least some exhaust under cowl or carb area, but I don't. And I could be totally wrong but seems it would start and idle different ?! If exhaust. But it starts good and good idle.
Thanks.

 

[oldboat1]

Saw some technical data somewhere on that air silencer -- sounded like a mid-year change or similar, point was to correct or handle some fuel leakage into the pan. Required a good gasket and use of some sealant.

The front looks like it has louvers with some air vents underneath, but maybe not. Think I would first make sure the carb is venting properly -- if running well without the silencer, though, probably fair to assume the carb is doing what it's supposed to.

You might find some plastic plugs at your local hardware store, and drill some holes of appropriate size in the face of the silencer, probably toward the top. The plugs allow you to fill the holes if you want to restore the silencer at some later time -- perhaps if you have an epiphany at some point, and discover another source of the problem.