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

[valvebounce]

I've had similar problems on cars ,bikes and concrete mixers,it's always been the lack of air.Usually a blockage in the air filter or intake.
When they say "improve the breathing" they put a less rest restrictive air filter on,and a less restricted exhaust,this usually adds more BHP.(on cars and bikes)
You may have a linkage interfering with the choke/primer,which would richen your mixture,which would be like running with the choke operating.By taking your airbox off,it would be giving the carb more air to deal with the richened mixture.

 

[jakedaawg]

I've had similar problems on cars ,bikes and concrete mixers,it's always been the lack of air.Usually a blockage in the air filter or intake.
When they say "improve the breathing" they put a less rest restrictive air filter on,and a less restricted exhaust,this usually adds more BHP.(on cars and bikes)
You may have a linkage interfering with the choke/primer,which would richen your mixture,which would be like running with the choke operating.By taking your airbox off,it would be giving the carb more air to deal with the richened mixture.

Good point valve bounce...

Highdog1 When you are running your motor what position do you have the red lever in? Is it parallel with the solenoid body or perpendicular?

 

[Chinewalker]

Any chance the carb silencer is pinching the fuel hose when you install it? Don't ask me how I know to check that.

Also, does it run with just the silencer cover off, not the base?

 

[Highdog1]

oldboat1 - I've looked on the parts list for that year/model and the silencer box is slightly different , so I'm not sure if they changed them out at some point for any problem issues. It came with the boat and never had any problems before with it. On this one there are 3 good size hole shapes on the starboard side of the silencer box. Those are all good and cleaned out. I had thought about that too, just drill a couple of holes into the plastic cover to let more air in, but a buddy of mine said I may just be band aiding a problem going on. Hence, my quest to see if something else could be going wrong. And to no avail thus far! Thanks for your reply.

 

[Highdog1]

valvebounce - The primer solenoid is located above the linkage and not able to really block the linkage. I disconnected the hoses to the carburetors from the solenoid and when I push the key in it comes out and release key back out it stops, so I figured it's doing okay on that. And I set the carbs to pretty much where the engine has always been happiest with , but one thing I've not done is a drop test. I've done compression, spark, and thought it was fuel related. But most the posts here concur it's an air issue. I just rebuilt the carbs.
Thanks.

 

[Highdog1]

jakedawwg - That leads my back to my fuel question and any input would be greatly appreciated. I replaced the fuel hoses to the carbs and they're not pinched, but since these new hoses are the bright yellow in color I've been able to see the fuel. The top carb hose seems to have air bubbles that I don't see in the bottom hose. Is that a normal? The old hoses were black and I could never see the fuel. So I wasn't sure about that. And this issue with the fuel tank may be nothing, but it's an attwood 6 gallon tank said it was self venting. Well about a month ago heading back to the dock I noticed the gas tank was pretty sucked in! So i loosened that cap and let the pressure out slowly and figure the cap, which has a little white tiny ball on the inside may have gone bad. So I've just been loosening the cap by hand whenever I take the boat out to prevent all the pressure and thinking it was still getting vented. Yesterday, since I've had the carbs and silencer box off waiting for my gaskets, the hoses are just disconnected. I must have tightened the cap back and it's pretty hot here in Florida right now , I smelled gas from the garage and went outside to the boat and saw gas squirting like crazy out of both carbs hoses. So I loosened the cap and hasn't done it since. Is it possible in any way that fuel with a faulty cap like that could not venting the fuel good enough? Possibly just loosening that cap isn't giving it enough air/venting it needs?
Thanks.

 

[Highdog1]

Chinewalker - The hoses are good. I've not had it out on the water with the whole air box off. I've tried a combo of the cowl on with silencer cover off, and it was fine. Cowl off , silencer cover on, won't go. Also, the fitting just under the carb where the vacuum hose connects , did have a little gunk in it. blew out with air.
Thanks.

 

[Highdog1]

jakedawwg - The primer solenoid red knob is parallel position with the very tip of knob facing towards the front of the motor.
Thanks.

 

[juno pierrat]

my red lever points aft, parallel along the primer body, just one more thing to try .also did this happen before or after carb rebuild

 

[Highdog1]

juno pierrat - the red knob is parallel along the body with very tip facing the carbs. The fuel tank issue happened after the carb rebuild.
Thanks

 

[oldboat1]

One of the standard idle adjustment tests after a carb rebuild is shifting and throttling up. Your air mix might be a little rich after your rebuild, particularly if using the old settings. Might lean out the mix a little and see if it still stumbles on throttle up.

 

[valvebounce]

I'm not familiar with your engine or carb,but there is maybe one basic thing to check,your float level in the carb.
if you have had the carb off and serviced it,sometimes the float level is disturbed,or the cut off valve on the float isn't seating properly.
This can cause the fuel in the bowl to be at too low a level,or,as in your case,too much fuel,which is similar to flooding the carb and running on choke.
Removing the airbox is probably giving the motor more air and dealing with the extra fuel.
Just one other point,if you have to open the tank cap to vent the tank it may be worth stripping the cap.They are sometimes prone to a slight blockage which restricts the venting.Probably not your main problem but just a thing to check.Even if you can blow through the vent,it can still have a gummed up deposit in it,the only sure way is to strip the cap.
The way to set your float level is to turn the carb upside down,the float should be level with the carb joint face.

 

[Highdog1]

oldboat1 - Initially I tried adjusting the air mixture screws while I had the boat out on the water and with the air silencer on. It didn't make a bit a difference except actually run worse or want to stall. So that's when I decided it was time to clean and rebuild the carbs. I made the adjustments on the carbs after the rebuild kits in the driveway on muffs but they actually ended up being what they always were. I noticed the top carb seemed to be a difference of quarter turn out from the bottom. But figured it wasn't to big a deal as long as it was responding good at the setting. No change in gas mixture. 50:1 ratio,. even changed my fuel out several times thinking I had bad fuel. No improvement. Thanks

 

[Highdog1]

valvebounce - I have rechecked the floats a couple times now and pretty sure they are set right. But when I have the boat on the water and have the silencer off, I can see the high speed are good and fuel dispersing , but I also see a little more fuel build up in the throats. They both look almost greyish in color but figured that could be condensation getting in from having the silencer off and it's really humid here right now. But when I took my finger and wiped out , it's quite a lot, I can see the oil and gas.. When I put my hand over the carbs they do seem to be sucking in, but the silencer is off at this time so it will run ok. That fuel tank cap can't really be stripped, it's got a small round ball inside there. It definitely is not self venting. I'm thinking of just taking a separate gas can on the boat and test it that way. Is it even possible to have a scenario where when I loosen the cap it relieves some pressure on the fuel tank, but not actually getting vented well enough through that cap where pressure still builds blowing more pressure towards the carbs? instead of the carbs being allowed to suck in normally with silencer on. But with silencer off theres enough air for the carbs to actually suck in and go full throttle?
Thanks

 

[jakedaawg]

post some pics.

Did this motor ever run good for you?

 

[oldboat1]

...and readjust the needles in the water with the cover on. After rebuilding, sounds like you didn't readjust in the water (back pressure). When adjustment makes no difference, it's usually a sign of dirty idle passages in the carb -- think your intuitions were right.

 

[Highdog1]

jakedawwg - I'm having some issues trying to post pics I took. It says error PHP file exceed 2.00 MB. Not sure why it's doing that or what it means.
Yeah, the motor has run great for me til recent. I had some major repairs a couple years back. No problems, just usual maintenance.
Thanks

 

[jakedaawg]

Use a photo resizeing app.

 

[Highdog1]

No Title

 

[Highdog1]

oldboat1 - I will adjust them again on the water. They're pretty clean in there. Didn't soak, just blew out with compressed air and rebuild kits in both.. Still waiting on one gasket, hopefully be here tomorrow.
Thanks