1988 Johnson 9.9 low RPM and power at WOT.

[wvmedic]

1988 Johnson J10RCCD with Champion RL82C plugs.

I bought this boat and motor combo. When I got it home it had old gas in it and when I checked the fuel pump screen the gas that came out of it was brown.

So I decided to rebuild the carburetor and fuel pump as well as new plugs, I replaced the NGK plugs with the above set at .30 gap.

Took the boat out with a new gas tank and hose, it ran perfect like new.

Took it out about a month later couldn't get it to start, I took the silencer off and soaked a rag with gas pumped out of the fuel pump held over the front of the carburetor.

It fired right up and idled fine, shut in down and it fired up first pull. In fact about a half of a pull on the rope, ideles fine.

Head out on the lake and it will not rev up to full RPM at WOT. Atleast by sound and speed as it did on the previous run. It will pick up RPMs if I pull the choke out about a 1/4 of the way.

Took it out again yesterday, same thing. Got home and took the carburetor apart and found what looked to be a small piece of teflon tape in the bowl. I haven't used any teflon though.

So I blew compressed air thru the carburetor to make sure that it was clear. Put it back together and hit the river this morning and it is still running poorly.


Compression is 120psi on both cylinders, good spark jumping a half inch on the spark testers.

I am at a loss as what is wrong, any ideas?

I have to get it working correctly because we leave for Quebec in 66 days.

Help, please

Jeff

 

[bonz_d]

Was running perfectly and now not. Sounds like you still have a fuel blockage in the carb. Tape, no clue where that could have come from I think you are going to have to look it over very closely.

 

[jakedaawg]

I would suggest cleaning carb completely, replacing fuel lines from cowling to pump and from pump to carb, and double check proper installation of fuel pump rebuild kit.

 

[jakedaawg]

I always thought that engine ran a QL77JC4 but the 82 could be an acceptable replacement, I'd have to look up the manual and those old ones are packed away. Either way, it does not explain the fuel issue.

 

[wvmedic]

bonz_d, thank you.

jakedaawg, thank you.
You are correct on the plug number. Although the Ql82c is an acceptable replacement, the RL82C is not.
I have just read something about a resistor plug V/S the Q plug. The resistor plug supposedly can cause WOT problems.

I am going to try the QL82C and see if they help. I want to run them because they are a little hotter, I do a lot of slow trolling in Canada.

I will also have new fuel line on hand to change after I see if the plugs make a difference.

Jeff

 

[rasteele]

My 1990 9.9 does the exact same thing, cleaned the carbs probably 5 times. But I never noticed the high speed jet on the big bulky part in the bowl. I took it and it was mostly clogged. Now I have super great throttle response but I still haven't water tested it as I had to go back to work today. I will watch this post and let you know my findings also.

 

[wvmedic]

If had the carburetor timing off, would that cause my problem?

 

[AlTn]

at wot..is the throttle plate exactly horizontal in the carb throat?...is the carb roller to the highest point on the timing cam?..if the answer to both is yes, then that's in time at wot for that engine....you mention something in the carb resembling teflon tape, some of the ethanol resistant fuel line has an inner lining that resembles teflon tape...maybe a piece of it delaminated < if that's how's it's made > and got to the carb

 

[wvmedic]

Upon inspection this morning, no it appears that the throttle was not opening up all the way. I redid the sync and now the throttle is opening all the way.

 

[wvmedic]

Well, I put some clear fuel hose on between the fuel pump and the carburetor. Noticed I was getting large air bubbles, so I put zip ties at both ends. The bubbles went away.

Motor opens up to WOT now without problems.

I'm getting 11.5 MPH out of it by GPS.

Was getting around 13 MPH before with the Wife and I.

I'm 260 pounds, Wife 140. Does the 11.5 sound normal for a 14' aluminum boat and my load?

The boat is a Lowe 140v.

Jeff