Low RPM at WOT

[Skider]

Hi Folks,

Motor Type: Johnson OutBoard
Year: 1982
HP: 140

I have a problem with Low RPM's WOT at ~3,000RPM.
It runs at this RPM without stalling or backfiring.

The motor also runs poor at idle as well and requires the high idle lever to be
pushed up before going in to gear or it will stall. It also will backfire at
idle while in neutral.

I can run the motor in neutral using well above 3,000RPM's.

I have done the following service on the motor this year before the
RPM issue started:

1. New UL77V Spark plugs. Torqued to 19Ft/lbs
2. Drained Fuel tank and added Sta-Bil after added new regular gas
3. New Fuel line between new primer bulb and engine fuel connector.
4. Replaced lower unit oil.
5. New battery

Last time I ran the engine it had not issue at nuetral idle or WOT RPM.
It has been a reliable engine but has had not been used for many years
before this issue started.

Any help on this issue would be great.

Thanks in Advance,

 

[SKEETR]

Re: Low RPM at WOT

rebuild/clean carbs. Bet she'll run like a champ.

 

[Skider]

Re: Low RPM at WOT

Thanks for the reply Skeetr!

I will give that a try. The boat has been alot of fun in the past and hope
to have alot more with it.

Is it possible the timing is not correct?

Regards,

 

[SKEETR]

Re: Low RPM at WOT

It is posible, but generally speaking that adjustment doesn't change with non use. Someone would have had to made adjustments to the linkage settings to throw things off. You will, however, need to become familiar with your linkage in order to sync the carbs after the rebuild.
If you feel someone may have made some adjustments to the linkage check and see if they are in sync. Do the throttle butterflies open together and are both flat and equal in the WOT position? Remove throttle cable to test.

 

[Skider]

Re: Low RPM at WOT

I am the only one to service the engine since it was last run and no adjustment was done on the linkage or throttle cable area. I just
put new spark plugs in it at the start of the summer season.

I will check the butterfly opennings and let you knowmy finds.

Thanks for the help.

 

[ThePerchik]

Re: Low RPM at WOT

I had a similair problem and took a look at the spark plug wires which looked old and were not very secure on the new plugs. Swapped them for new ones and she ran like a champ. One was misfiring, it was really shaking and vibrating wierd.

 

[Skider]

Re: Low RPM at WOT

Hi Guy's,

The problem of LOW RPM has been fixed.

I Changed all the spark plug wires and Rebuilt both Carb.'s.

I cleaned out the Choke hoses and replaced a few fuel hoses
that looked cracked.

Now I have too many RPM's at WOT! Ha Ha Ha Ha!

I talked to my local OMC repair shop and they think the Prop is not
set correctly. I think it may be the timing since I did turn the
throttle adjustment a little bit to seat the stop positions of the
idle. It also moves the timing advance position at the same time.
I will move it back to the old position and see if that corrects
the WOT HIGH RPM issue.

Thanks for your help guy's,