How to clean exhaust 9.9

[gooden123]

I have reason to believe my exhaust is plugged causing it not to achieve full RPM on a 1992 9.9 Evinrude. I don't need any diagnostics for that. I dropped the gearcase and extension both of which are loaded with sludge. It's been running rich for an extended time. That's been resolved, just need to find a way to clear as much of this sludge as possible without powerhead removal, for now. I was thinking engine tuner thru the carb, let it soak overnight, blow it out on a flush kit so exhaust isn't restricted. Repeat. Right track? Thanks and happy father's day, father's.

 

[gooden123]

Exhaust extension for example

 

[flyingscott]

Put it all back together. Then run it up to temp and spray Ring free, engine tune or something similar through the engine. But you can look straight up the exhaust tuner with the lower unit off.

 

[gooden123]

Put it all back together. Then run it up to temp and spray Ring free, engine tune or something similar through the engine. But you can look straight up the exhaust tuner with the lower unit off.

Thanks Scott. Kinda figured that's about all I could do. I don't know jack about exhaust systems but I imagine there isnt much to them. Just didn't know if I should be probing or spraying anything before putting it back together. My other OMC's spray a little water out of the muffler above the waterline and this is always dry. Looking at it I guess there shouldn't be any water but don't know why my others do. They run fine, this one doesn't.

Compression 120 (both)
Spark jumps 3/8", with advanced throttle too
Flywheel key okay
Correct jet in carb
Carb rebuilt with OEM kit (3 times)
Float is set level
Sync and link done
New correct plugs L77JC4 .040 gap (also tried QL82C .030). Both recommended

 

[gooden123]

Sorry, it's not going over 3400 rpm. Not running rough or anything. Fuel mix is correct, tried 2 other tanks/lines/primer bulbs too. Usually it only gets 4400 because I'm underpowered for a 10 hp lake. But I can't even plane now. Usually I get 14 mph, now I'm at 7

 

[flyingscott]

As far as not reaching top Rpm make sure the carb is opening all the way. Those rollers and arm assembly are not the most durable. How do you know its only reaching 3400 rpm.

 

[gooden123]

As far as not reaching top Rpm make sure the carb is opening all the way. Those rollers and arm assembly are not the most durable. How do you know its only reaching 3400 rpm.

I have a tach. It's remote control 9.9..even if it's not spot on I'm going 6 mph and not 14. Just needs a little more umph then it'll plane. The roller is perfect, so is the throttle cam. No cracks, grooves or anything. Everything is lined up and throttle cable adjusted to pull wide open. Throttle plate is open flat and not over rotating. Only things I haven't checked are the fuel pump but priming the bulb makes no difference and looking at the sludge (and plugs) I'm getting plenty of fuel delivered. And I haven't omitted the primer solenoid but it only squirts fuel when I push the key in. Oh reeds are good. No blowback anyway and it isn't running rough. Prop is new OEM 9.25×8 and was perfect for it. Never touched bottom. One day I ran it all over, put it on the trailer, no issues. Next day it wouldn't go over 3400 right off the bat. This is why I'm in the exhaust because I'm out of components to double check.

 

[flyingscott]

Make sure the primer is not leaking by.

 

[gooden123]

Make sure the primer is not leaking by.

I'm doing a seafoam treatment on land now. Running several ounces then loading it up till it stalls, 10 min soak, blow it out, repeat. Lots of sludge draining if nothing else. I don't ever run this thing on land because it's freshwater only but I'm going to make a habit of it just to blow out residual fuel since it never achieves real high rpm in water. I wouldn't Rev it up on a flush either but no back pressure on exhaust should clear it. When I get new plugs after this and go to the lake I'll eliminate the primer if it still has problems. Doesn't need it to start in warm weather anyway. But if I push the key in while running it stalls so I don't think there's a problem there unless like you said, a minute amount is seeping