1985 Johnson 150, misses at 1500-2000 rpms

[hall832]

1985 Johnson 150 has new coils, new power pack. Carbs are rebuilt. When I run it up not in gear its fine. I put it under a load and it idles perfect but whem i bring it up past 1400 rpms there is a definte miss. then when i get past 2100-200 rpms its fine(no miss) gets up to 4800 rpms. Thats it WOT. Prop is correct. Not sure if its stator or timer base. Compression is within of 5 of each cylinder. I know i need a peak meter. I have ordered it. I just was wondering if you can tell me what you think. going crazy.

 

[schematic]

Re: 1985 Johnson 150, misses at 1500-2000 rpms

First guess would be :

-crap behind welch plug in carb
-warped float bowl
-over-propped as well

also check fuel pressure...

 

[hall832]

Re: 1985 Johnson 150, misses at 1500-2000 rpms

As well as the rmp miss i am finding excessive fuel in all over the carbs and leaking doen the cowling. I pulled the welch plugs on all three carbs. Nothing in there. Cleaned them will brass wire. new neddles and seats.

 

[emdsapmgr]

Re: 1985 Johnson 150, misses at 1500-2000 rpms

If the engine runs fine at WOT (4800 rpm's), doubt it is a fuel delivery problem to the carbs. Possible that the mid jets may have some crud in them. When you were in the carbs, did you pull all the jets out and visually inspect them? Agree that the engine is overpropped. It should be propped to run at least 5500 rpm's. You are lugging it at max rpm's of 4800. Pump up the fuel bulb and see if you can determine just where the fuel is leaking from under the cowling. Check not only for cracks in hoses, but loose clamps. Your carbs have the good aluminum bowls-unlikely they are warped.

 

[hall832]

Re: 1985 Johnson 150, misses at 1500-2000 rpms

Thanks for responding, carbs were clean. All jets clean. Found fuel leak. Still need help on the miss. Think its trigger or stator. Also checked rectifier. That's good.

 

[hall832]

Re: 1985 Johnson 150, misses at 1500-2000 rpms

Prop is 14 1/2 x 19

 

[emdsapmgr]

Re: 1985 Johnson 150, misses at 1500-2000 rpms

The factory service manual has a couple tests for both components. Ohms and volt output. There is an output spec for both the stator and the timer base. Check your service manual regarding cranking output voltages from each component for your model year. The timer base may be something like either .2 or .3 volts. The stator may be in the 200 volt range. Less than these outputs and the component is condemned. Voltages measured with a special "peak-reading" voltmeter at normal cranking rpm's (250.)