low speed and idle not happening

[riktweed]

Our 1966 Johnson 80 runs great at mid to full throttle, but refuses to run at low speed or to idle. This problem is worse when in the water, but even on the muffs it doesn't idle well and dies after less than 1 minute.

We have new plugs getting strong spark and fresh 50:1 fuel, have set the distributor/throttle linkage by the book, and have good compression.

We set the low speed needles all the way in and back out 1.25 turns to start, but adjusting them further to smooth out the idle seems to have little noticeable effect. We also have copious amounts of unburned oil oozing out of the exhaust.

We are about to rebuild the carbs and would appreciate any other suggestions or possible causes we have not addressed. Thanks!

 

[DargelJohn]

Re: low speed and idle not happening

When you have the carbs off, check the intake manifold gasket or anything else that might cause air leaks.

 

[Tim Frank]

Re: low speed and idle not happening

I would check the compression.

 

[riktweed]

Re: low speed and idle not happening

The compression is good at 120-123 lbs per cylinder.

It runs great at mid to full throttle, very fast with good pickup. The motor is on a 16' MFG Westfield Custom.