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1993 30hp has part throttle miss, idles rough

M

mixin

Member
Hello,

Dealing with a J30TELETA here, engine starts fast, accelerates well and has lots of power up top. But at light throttle (2,000 RPM I would guess), where the boat is not on plane, the engine runs well for 3-4 seconds then cuts out for a split second and then repeats the process. The engine also idles rough and stalls easily when putting in gear, especially when cold.

The motor was just purchased. I mixed a tank of fresh fuel and checked the fuel filter screen. Besides general greasing and lower unit lube, I have changed the plugs and run a can of power tune through it. Any ideas on where to start troubleshooting?

Thanks!
 
Suggest you give it a treatment with Sea Foam/Engine tuner and then a properly synch of carb and ignition.
Got a proper workshop manual?
 
No manual yet - it's my father-in-law's boat, I am trying to help him out.

I used an aersol can of PowerTune that I sprayed in through the carb last week. I saw a can of PowerTune at the boat shop that hooks up to the "schrader valve?" on the primer, if I use this, will it then run through the fuel passages on the carb to clean it out? It seems that the miss is in the RPM range that you are supposed to run the motor at while doing the PowerTune treatment - maybe if the treatment runs through the fuel passages, it would clean it then?

Is there a way I can check the synch to at least see if it is out of adjustment?

Thanks!
 
Assuming that the cutting out thing is actually having a spit back condition (sneezing of the carburetor type thing), the following would pertain.

That cutting out for a split second, then going thru the process again and again would indicate either a lean setting of the carburetor or having the throttle butterfly starting to open too soon.
 
Makes sense Joe.

Due to my lack of experience, I do not know what a spit back condition sounds like...I know that it did not backfire through the carb, but it "felt" like a mixture/fuel issue since it was doing it every so often at a regular interval and only at a certain RPM range.

Would this also contribute to a rough idle? Sometimes when I idle and put it in gear to take off, if I accellerate slowly, the engine will take a second to "catch up" to the throttle input I give it and then it takes off. - Is this indicative of a sync issue as well?

How can I check/set the throttle sync issue?

Thanks for your help!
 
In doing some exhaustive searches for the sync process, I found that the usual reply is "get the manual" since the procedure is different for each model. I ordered the factory service manual for 1993 Johnson 9.9 - 30hp from searayman13 on ebay - good price! Hopefully this will get me started in the right direction. Any other advice would be greatly appreciated in the meantime!

Thanks!
 
Not too big a problem.
1: See to that the carb starts to open just as the follower is between the two marks on the cam on the armature plate under the fly wheel.
2. Put engine in gear (not running) and give full throttle.
Adjust the stopper on the link on port side so the carb is 99-100 open.
2: Start the engine, preferably with boat in water or engine in a barrel.
Let it run to operating temp. (check cooling and thermostat function).
At the lowest possible throttle, adjust the idle mix until engine has the highest rpm, then back off the idle mix screw about 1/4 turn.
Do a test run.
Note:
I always recommend to give the engine a good run down with Sea Foam/Engine Tuner BEFORE adjusting!
 
haffiman37 said:
Not too big a problem.
I always recommend to give the engine a good run down with Sea Foam/Engine Tuner BEFORE adjusting!
Click to expand...

I was going to buy the BRP PowerTune that looks like to attaches to the fuel system of the engine at the primer - would you recommend this product and method of using it? If you greatly prefer the seafoam over BRP PowerTune - I will try that instead.
 
I think the old Engine Tuner has been renamed Power Tune.
Follow the instructions on the can for best result!!
When injecting through the primer solenoid, use your finger directly on the carb butterly so the engine does not stall too early.
 
haffiman37 said:
I think the old Engine Tuner has been renamed Power Tune.
Follow the instructions on the can for best result!!
When injecting through the primer solenoid, use your finger directly on the carb butterly so the engine does not stall too early.
Click to expand...

I used a can of the aerosol PowerTune last week and sprayed it in through the carb - followed directions, let it soak for 8hrs and then ran it out for 30min.

Is the PowerTune that attaches through the primer solenoid better? Or should I just get another can of the aerosol kind? Thanks!
 
The "Spit back thru the carburetor" condition is best described as a mild backfire. That is, it is not the shattering loud backfire as one would know it being shot out the exhaust housing but rather a small jerking of the engine coupled with a small short air blast sound.
 
Keep in mind that engine tuner will not clean out carb circuits. It sounds to me as if you may have clogged idle circuits, which would require pulling and cleaning carb(s). Do not soak carbs in solvents, as this can destroy the finish(coating) which prevents air being sucked through the porous surface of the carb.
 
Ok, my father-in-law ran three doses of the seafoam "shock treatment" through it in a barrel. (16oz of SF, 1gal gas, 3oz oil) - 15 min run, 15 min off each time. I'll try to get it out on the lake this weekend and see how it does. Thanks for the help, I'll report back with results. Thanks!

Mike
 
Update

We took her for a ride two days ago - she still is very cold blooded and stalls easily during the first few minutes and smokes alot (this may have been some residual seafoam - even though it was run on muffs with regular gas/oil mix for 5-10 min before by my father-in-law). The engine runs much smoother in the lower to middle part of the powerband with no "puffing" through the carb (the cutting out I was describing before), (except) for one isolated instance at a very specific RPM after running for an hour or so.

So, the engine runs MUCH better - I am a believer in SeaFoam! But the motor is still not 100% - so I think we are headed torward a carb rebuild to fix it right.

I do have a factory service manual for the specific year of the motor - any bits of advice before begin the carb rebuild? Thanks!

Mike
 
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