1986 Johnson 110 HP

[jmrieck]

Motor will not reach 5500 rpms at wot. Under load it will only reach 3200 rpm at wot. Have checked compression all 4 cyl are at about 110. Checked all plugs by unplugging during idle and there is definite change when I unplug each one so coils are good.Is it just a plugged gummed up carbs or maybe an electrical problem? Any help appreciated

 

[AEROCOOK]

Could be a lot of things but as a start, I'd check the carbs / linkage and make sure they open all the way when the throttle lever is fully advanced.
When was the last time it had a link and sync?
Is the motor new to you?
Has it ever run at 5500+ RPM since you've had it?

 

[jmrieck]

I did check the carbs to make sure they were open all the way with wot the carb plates are all the open.never had link and sync don't really know what that is.the motor was put on by me this summer and it has never run at 5500 rpm. The motor sounds great when running on the water but won't hit optimum rpm

 

[emdsapmgr]

Compression is solid. The spark-drop test you did seems to confirm all plugs are firing. That's good. Overhauling both carbs may be the next step.

 

[jmrieck]

Ordered carb kits today. Will rebuild hopefully this weekend try to get a lake test in on Sunday .will post to let you know if all is well fingers crossed. Thanks for the help.

 

[Dave Abrahamson]

What are you running for a prop?
Could be too high pitch maybe?

 

[jmrieck]

Already did a prop change went from 17 pitch to an 11 pitch gained about 500 rpm and some speed but before I did that it was only running about 2800 rpm at wot. This motor by the way is on a 24' pontoon boat

 

[jmrieck]

Well I rebuilt the carbs changed plugs and wires and put on new feul hose and squeeze bulb plus a new fuel filter. Really wanted this done sooner just didn't have time. Well anyway I took boat to the lake and still same results only about 3200 rpms at wot. Dont know what to look at next. Any help would be awesome. Also getting a little sneezing when trying to start her up

 

[racerone]

Flywheel key checked ?-Something is wrong as you should get more than a 500 rpm change when you change 6" in pitch !!!--Did you remove the high speed jets that are screwed into the very bottom of carburetor bowls ??

 

[emdsapmgr]

The 11 pitch prop is more appropriate than a 17 on a pontoon. Still you did not gain much rpm. That's a strong engine and it should be really performing with that 11 pitch. Have you checked the tach setting on the back of the tach? Engine mounted too low on the transom?

 

[jmrieck]

Did remove all six jets in the carb and cleaned them up really well. Will definitely check the flywheel key I'm assuming that if its sheered even a little it will throw timing off enough to make it run the way it is? As for the motor maybe being too low, when I put the new prop o. I had to lower the motor all the way because it was " blowing out "in the turns so can't raise it anyway with this prop. When I changed from my previous engine" 1999 Johnson 50 HP" to this engine I also moved the switch on the tach to position # 6 thanks for the input people hope to get it going soon summer about over

 

[jmrieck]

Flywheel key is fine so I guess I'll check the timing and make sure its OK. After that I don't know what to look at next. Thanks for the input.