Logo

b70 Johnson 60HP clogged carby

sashko1

Contributing Member
"I've been fighting with t

"I've been fighting with this motor for 2 weeks already. I'm at the point of a big regret and despair.

Initially it wouldn't start. Cleaned distributor, all electrical connections - was able to start.

Took it to the lake - motor runs slow. Checked spark plugs - all wet. Bought new ones: QL77JC4. Tested with muffs - worked somewhat better - thought I fixed it. Took it to the lake - runs much faster but not as I've been told 40+MPH, but only 20MPH.

Checked spark plugs at the shore again - #1 and #2 cylinder plugs are brownish and quite dry, but #3 is like new (not brownish) and very dry. Checked for spark on it - YES there is a spark!

Does it mean that the fuel is not getting to the cylinder? Are we talking clogged high speed orifice/jet or whatever it's called?"
 
"Sounds like your onto somethi

"Sounds like your onto something, when testing a problem like this i like to spray some carb cleaner into the carb while it's running, if it shows improvement then you've found the problem, if the engine dies out or runs rougher then that carb is probably Ok as now you'd be giving it to much fuel.

Sounds like the bottom carb needs some attention."
 
Great! Thanks for response.

Great! Thanks for response.

Where do I exactly spray the carb cleaner? Into the air intake?
 
You would need to take the air

You would need to take the air box off the front as you need to be able to spray directly into the carbs.
 
excellent. Will do it this Sat

excellent. Will do it this Saturday. If I spray some carb cleaner is it supposed to clean the carb? or is it just to verify that the carb is bad?
 
"How do You intend to get the

"How do You intend to get the carb cleaner into the carbs by spraying into the carb throat?
Carb cleaner is for carb internals like float bowls, jets, channels and should NEVER be sprayed into the engine as it wash all the oil film away."
 
"You can use carb cleaner to d

"You can use carb cleaner to determine which carb is lean or rich by spraying into the carb while the engine is running, doing this at different speeds idle or under load attached to a trailer or running on the lake.

You only need one short burst of spray to hear the engine respond, If you want you can also put some fuel into a spray bottle, does the same thing, it's just what is handy.

The amount of oil it washes away from the carb or intake is negligable and probably needs to be washed away if the engine hasn't been running on that carb, thereby building up an excess of oil, not that, that is a bad thing."
 
"you can also achieve the same

"you can also achieve the same effect w/o risk of washing lube away by using unlit propane torch to feed propane into air intake of running engine....this is one way to test for vac. leaks at gaskets on cars.

my take would be that if it's a 38 yr old engine and you don't know when the carbs were last rebuilt, do em before you start driving yourself nuts trying to troubleshoot other sources...??"
 
"'You can use carb cleaner

"'You can use carb cleaner to determine which carb is lean or rich by spraying into the carb while the engine is running, doing this at different speeds idle or under load attached to a trailer or running on the lake.'
'you can also achieve the same effect w/o risk of washing lube away by using unlit propane torch to feed propane into air intake of running engine....this is one way to test for vac. leaks at gaskets on cars.'

There is NO oil in either carb cleaner or propane!!!!!!!!!!!

If You want to spray anything into the carb throat when running, use a 2% fuel oil mix, fogging oil, engine tuner whatever as long as it lubricates."
 
"yes, you are right there is n

"yes, you are right there is no oil in Carb Cleaner or propane. but in a pinch and only used briefly and where as the engine is already running on fuel/oil mix how much damage will it do, will it do any damage? sounds like we need mythbusters here..

as another great mariner said, "Any Grease is better than No Grease/Oil, at all!!"

Safe Boating !"
 
"There is a reason I'm tha

"There is a reason I'm that strong against anything else than fuel/oil mix in the carb throat,and that is by experience.
A customer of mine managed once to blow his 9.9 to pieces by a similar trick as You describe. The flame point of carb cleaner and propane is far lower than the fuel/oil mix. If unlucky and a crank case combustion .......!
On a 4-stroke it might be less risky, providing the valves does not leak, but NEVER on a 2-stroke!"
 
"Updates ...

Disassembled a


"Updates ...

Disassembled all 3 carbs on Saturday. Suspected #3 carb had a stuck float needle for some reason (?), so that it wasn't letting any fuel into the carb!

I didn't see any flaws in the rubberized tip of the needle though. Cleaned everything with the carb cleaner. During installation I made a mistake - since I didn't have new gaskets, I decided to reuse the old ones. Later found out that I have some fuel leak from the gaskets
Oh well, ordered new ones, will get them this week (hoping).

But, anyways, the motor fired up great! Checked all three cylinders individually. And then after fighting for some time with low speed adjustments, and after I reconnected all three spark plugs to their original positions, MAN I LOVED THE SONG THAT MOTOR SANG!
))

Next steps: 1) install new gaskets; 2) install safety cut off switch; 3) re-weld supporting bracket at the trailer; 4) some waxing; 5) LOTSA boating
))

Thank you guys for your support!"
 
"Morten--

your point on exp


"Morten--

your point on explosion risk is well taken! most of my 2 stroke experience has been with motorcycles and i don't always think of the marine issues. this is enough reason to avoid my good idea.}
on the lube Q, tho, i respectfully doubt the slight richening of mixture from propane of a motor already running on correct fuel-oil mixture will cause any lube problems.}"
 
Back
Top