Johnson 85hp problem

I have a 1976 Johnson 85HP that is giving me fits.

I have between 98 and 105 compression on all 4 cyls, new plugs, new carb rebuild, and all new fuel lines. It starts fine on muffs, and everything works perfectly. I can put it into gear, run it up to a slow run and 0 problems.

When I put it into the water, it runs great, I can put it into gear and it still runs good (better sounding then on muffs) and it will go to a fast idle with no problems at all. Then I get to the end of the no-wake zone and try to open it up. Now it does fine on muffs, but as soon as I push the throttle past fast idle, it just dies. I'll start back, but it just quits like the key was turned off or something.

I rechecked my coils and they were fine, timing level is free and moving properly (I did notice that it dies after the end of the timing lever travel when the throttle moves past the max advance) and I can't find a single thing wrong with it.

Any idears?

Re: Johnson 85hp problem

Someone more knowledgeable than I will surely come along but............. off the top of my head, I'm thinking you need to do a link 'n synch on your carbs.

Re: Johnson 85hp problem

Sounds to me like you have possible blockage in your carbs. When was the last time you pulled them apart and put a rebuild kit in them? Are all of your fuel lines newer alcohol resistant? If you are getting good spark and you haven't pulled anything off of the motor that would mess up the carb synch or timing then I would lean towards a fuel issue.

Re: Johnson 85hp problem

Check for blockage in your high speed jets.

Re: Johnson 85hp problem

Gideon_70 said:

I have a 1976 Johnson 85HP that is giving me fits. as soon as I push the throttle past fast idle, it just dies. I'll start back, but it just quits like the key was turned off or something. I did notice that it dies after the end of the timing lever travel when the throttle moves past the max advance.

Click to expand...

The high speed jets are somewhat fouled/clogged (2 to a carburetor - 4 total). Remove carburetors, clean and rebuild. Be sure to manually clean the brass high speed jets with a piece of single strand steel wire as carburetor cleaning solvent in itself just doesn't do that job properly.

Re: Johnson 85hp problem

The carbs were rebuilt last year and put in storage after. I cleaned them anyway before I started and they were perfect. I also replaced all of my fuel lines with new ones, just in case and made sure I had good fuel delivery. It doesn't sound like it's starved for fuel, it just dies as soon as it goes from fast idle to beginning of WOT like someone turned the key off. Easing into it doesn't help.

I'm thinking that the linkages were messed up and going over that now. Still trying to remember how to set slow idle timing and pick up.

Re: Johnson 85hp problem

Thanks for the reply. The carbs were rebuilt and never run after until I bought the boat. The engine runs past the dead point if there is no backpressure. I just bought this, and have been running down issues for weeks now.

Re: Johnson 85hp problem

To the untrained ear, that engine will seem to run fine on two or three cylinders when on a flushette but obviously it is not. However, at the lower rpms, restricted high speed jets will allow sufficent fuel to pass thru to have engines run properly on all cylinders when the compression and ignition is normal.

The compression could be better... on that model usually in the 125 psi range but the readings you quote could simply be the gauge used.

Unless you or someone else changed the measurement between the vertical throttle arm and the yoke at the end of the threaded arm, or loosened and changed the position of the throttle roller, the link and synchronization should be fine.... butterflies start to open when scribe mark on cam aligns with center of roller.

With spark plugs removed, the spark should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it?

If you have compression and spark, that type problem spells fuel. Have you actually double checked and, with a piece of single strand steel wire, actually cleaned those four brass high speed jets? If not, it might be a good idea to do so.

Re: Johnson 85hp problem

Mine is 76 Johnson 85 HP. If I just launch my boat and the motor is not warm enough, my motor will die when I open the throttle slowly. It seems there is a shift range between the fast idle and the "normal" forward speed that the engine will die. My solution is to push the throttle/gearshift lever quickly to bypass the "dead" zone.