3 different forums and no solution for 9.9hp lack of power

[ba_50]

1992 Johnson 9.9 J10RENA idles great but won't get up on plane.

It has a new carb kit, redesigned carb cover, fuel pump kit, spark plugs, fuel lines. and a fuel filter between the fuel pump and carb.

The carb has been cleaned about 10X. The high speed jet was clean when I took it apart the last time.
There is a 1/2" spark jump
I adjusted the idle cam screw to be on the mark when the throttle started to open and the left cam screw at full throttle withe the roll pin straight up and down. It helped some because at full throttle the motor lost power then came back up some when reduced before. Squeezing the fuel bulb doesn't help get any power.
I put soap suds on the gaskets looking for blow by and they looked ok.
Compression was 122# and 120#.
The float looked level.

It ran fine before I got that new carb cover. The original roller broke.

What am I missing? Thanks.

 

[Howard Sterndrive]

Re: 3 different forums and no solution for 9.9hp lack of power

It helped some because at full throttle the motor lost power then came back up some when reduced before. Squeezing the fuel bulb doesn't help get any power.

What are the rpm's doing when the motor loses power?

Is it lugging?
Or revving wildly?

 

[tx1961whaler]

Re: 3 different forums and no solution for 9.9hp lack of power

A couple of ideas to try, even though they are a pain:
Try putting an inductive timing light on each plug wire to make sure it's sparking under load. You gotta do this under way on the water.
Also when under way, try manually moving the carb linkage to open it up. I guess you can check this on land (not running) to make sure it's opening all of the way at full throttle, and confirm that the butterfly is opening up all of the way.

 

[tashasdaddy]

Re: 3 different forums and no solution for 9.9hp lack of power

are you sure there is not a pin hole in the fuel pump diaphram, that would cause flooding at high speeds.

 

[R.Johnson]

Re: 3 different forums and no solution for 9.9hp lack of power

Even thou it has been apart several time's, that sounds like a carb float upside down. I have found this more than once after someone rebuilt the carb.

 

[ba_50]

Re: 3 different forums and no solution for 9.9hp lack of power

It is lugging.

 

[coolguy147]

Re: 3 different forums and no solution for 9.9hp lack of power

well so if everything is supposedly ok just a guess what kind of boat r u running it on? is it propped correctly? for ur kind of boat?

 

[Howard Sterndrive]

Re: 3 different forums and no solution for 9.9hp lack of power

How does the gear lube look in the lower unit?

 

[R.Johnson]

Re: 3 different forums and no solution for 9.9hp lack of power

What is this new, or redesigned carb cover. Do I have this right? The engine worked OK before this was added. What is the idea behind this new cover?

 

[Chinewalker]

Re: 3 different forums and no solution for 9.9hp lack of power

I think he has one of the carbs where the top half of the body is plastic. I've had a few where the anchor point for the throttle arm is broken - I think the "new" style had a beefier anchor point.

In any case, this sounds to me like you've got a spark issue. Idles fine but no power is usually a spark issue/running on one cylinder. I doubt it is a head gasket as your compression is good and even. The top cover of the carb might affect the low speed circuit, but I don't think it involves the high speed. In any case, verify spark under load before tearing into the carb again...

- Scott

 

[Mas]

Re: 3 different forums and no solution for 9.9hp lack of power

Could timing be slightly off? Check for sheared flywheel key.

MAS

 

[iwombat]

Re: 3 different forums and no solution for 9.9hp lack of power

Nobody else noticed the fuel filter BETWEEN the pump and the carb? Now, I'm not familiar with that particular year, but I don't think there should be anything between the pump and the carb.

You should also try a different fuel line and tank. Lots of times this problem is an air leak in the fuel delivery. Might also want to check the gasket on the plastic carb top by spraying premix around the carb body. If it changes the RPMs your top is leaking.

Foamy fuel to the carb, or an air leak will do exactly what you describe.

 

[ba_50]

Re: 3 different forums and no solution for 9.9hp lack of power

The diaphrams in the fuel pump look ok and I reassembled it just like the manual said to do it.

The flywheel key is good.

The little rubber hose in the carb was 1/8" longer than the original so I cut it.
It may or may not have let the float needle close.

The carb top is plastic and they put a different low speed needle in it and there is no longer a bolt holding the roller on. No threads to go bad now.

I am going to try putting the 5/32" fuel line back on.

It is on a 14 foot open fishing hull and has plenty of power for this boat.
I change the gear lube 1x a year

 

[SkydiverX]

Re: 3 different forums and no solution for 9.9hp lack of power

what does it sound like running? have you tried different plugs? maybe the jetting is off.

 

[ba_50]

Re: 3 different forums and no solution for 9.9hp lack of power

I use the plugs they recommend. Tomorrow I'll put the timing light on it on the water and see what happens. It sounds normal at idle.

 

[Dunaruna]

Re: 3 different forums and no solution for 9.9hp lack of power

Can you please clear something up for me. Before the carb cover swap, did this motor get the 14fter up on plane?

 

[tashasdaddy]

Re: 3 different forums and no solution for 9.9hp lack of power

picture of the carb, let's see what you have.

 

[tashasdaddy]

Re: 3 different forums and no solution for 9.9hp lack of power

this is the 1992 9.9 carb, did you properly adjust # 23? #25 is the plastic low speed housing.

 

[floatingwoody2006]

Re: 3 different forums and no solution for 9.9hp lack of power

Had a similar problem with a yamaha last week. The throttle cable where it attached to the carb was adjusted too far forward with the set screw. a quick adjustment, and was all. good luck.

 

[ba_50]

Re: 3 different forums and no solution for 9.9hp lack of power

I'm not sure what you mean by adjusting #25. I adjusted the low speed needle and the # 20. #23 just screws in if you are talking about the high speed jet.

The spark tester showed it was firing at just below full throttle.

One other problem is it won't start unless it gets a shot of pre-mix. After that it starts first pull. The choke is closed.