johnson 48spl bogging down past 1/4 throttle

[CC Anton]

My Johnson 48SPL fires up and idles like a champ but can’t make it past 1/4 throttle without bogging down. New carb kit, fuel lines & gas tank, i.e. it’s not a fuel issue. It has been suggested that it’s an issue with the trigger but I can’t find any specs to test anything. Help!! (Please and thank you)

 

[juno pierrat]

What year? when at 1/4 throttle push key in, what happens, die of pickup?

 

[CC Anton]

What year? when at 1/4 throttle push key in, what happens, die of pickup?

I’ll try it and let you know. It’s a 1988. J48eslcc

 

[CC Anton]

When I ‘feather’ the choke it will rev-up and I am able to get to much higher rpms. What does this say?? Thanks!!

 

[CC Anton]

Holding the choke in with about 85% throttle I can get on plane.

 

[CC Anton]

When at 1/4 throttle and I push in key it dies.

 

[juno pierrat]

so i think its a fuel problem, the chock on these motors is actually a primer, those very small fuel lines from the prime dump fuel behind the throttle plate, basically bypassing the carb.. theirs no feathering the primer its electric , off or on. when rebuilding carb how did you set the float? did you run a small wire through all small holes in carb.? the bottom float chamber has the high speed jet in it, behind the float plug, needs to be open, small wire through it for sure.

 

[CC Anton]

By ‘feathering’ I meant intermittently pushing the key in.
The mechanic I bought this motor from said he had just re-done the carbs but I’ll open them up the clean those jets myself. I’ve done it before and it easy enough. Where should the float be set? Also, does the fact that she’ll get up to speed utilizing the choke decrease the likelihood of it being an electrical problem? Thanks for the advice!!

 

[CC Anton]

Also, I have a manual for this motor too now and I’ll check what it says about setting the float...

 

[juno pierrat]

the float is first installed on upper half of carb, turned upside down, it should be level with upper half edge. yes , not likely electrical. CC, I'm just a backyard fixer, supprised none of the guru's haven't chimed in. when reassembling go thru the link-n-sync procedure in manual.

 

[CC Anton]

Thanks for your input. I am also a back yard guy. I did the 3 carbs on my 75hp Evinrude (it has since suffered a piston ring failure) and I learned from my manual (plus YouTube) how to set those floats. Just checking if it’s the same. The manual for my 48spl says to use a float tool to set the height but I don’t have that tool. I also lack the timing light and tach tool to do the linkage synch so I feel a bit stuck.

 

[juno pierrat]

the link-n-sync is mainly the carbs fully closed( cam roller not touching cam) and then opening together, then the cam roller on the cam marks. the float is level or just a hair raised. also is the timer base advancing freely with throttle

 

[juno pierrat]

on the other major outboard forum now is a very good link & sync post from joereeves

 

[jakedaawg]

Yes, fuel issue.

1. Fuel sample from fuel line into clear jar. Look for phase seperation.

2. Disassemble carbs, remove orifices, clean thoroughly. Clear orifices of obstructions. Follow each fuel circuit path making sure they are clear. Assure floats are not heavy, weigh the same roughly.

3. Dont mess with the linkage when you remove the carbs.

4. If you have mixture screws count turns till seated before you remove them. This gets you a close starting point upon reassemble.

It's not a big deal. You probably dont even need carb kits but feel free to replace the parts if they appear worn or ratty.

Might as well replace fuel lines while you are in there. I like the Tygon brand fuel lines for anything after the pump. Easy to use and appears impervious to ethanol. I have some customers going on 10 years now and still fine.

 

[CC Anton]

Thanks for all the input! The timer base seems to lag a bit - it isn’t moving as freely as it should. How can this be addressed?

 

[jakedaawg]

Clean and lubricate

 

[juno pierrat]

remove flywheel, and check manual on taking apart timer base, while there look for dark gooey substance under charge coil and trigger, torque flywheel to 100-105 ft/lbs

 

[rowerowe101]

Would definitely thoroughly troubleshoot the fuel system befor taking off the fly wheel. Have you ran the fuel line on a seperate tank , and checked fuel pressure to the carbs?

 

[juno pierrat]

thanks rowerowe , getting ahead, chase fuel thing a little more

 

[CC Anton]

Fuel lines all check-out. I think the prob was the mechanic I bought it from definitely cleaned the carbs and replaced gaskets but forgot to reinstall one of the little gaskets that’s inside the bowl around the upright copper air-mixture tube...It’s all back together now (with missing gasket). I’ll let you all know what happens when I give ‘er a test run.