1999 40 h.p. johnson run-away problem

[randy0050]

hi,
Motor ran fine. Set up 3 years. Cleaned carbs and took out. Ran like a 10 h.p. ( sluggish ,bog down) Changed fuel pump and now when started, it runs out of control... Revs up and doesn't stop! The kill switch does not even stop it. It has few hours on it .It is a tiller motor. Any guesses Guys?
thanks in advance,
Randy

 

[ezeke]

Re: 1999 40 h.p. johnson run-away problem

Engines will run away like that when they need to be decarbed AND are run at high RPM with no load. Do not exceed around 1,000 RPM on any motor that is not loaded unless you are using a test prop.

The carbon gets red hot and keeps firing the fuel, which in turn keeps the pistons pulling more fuel into the engine. The only way to stop it is to cut the fuel supply or let the engine blow up, whichever comes first.

 

[randy0050]

Re: 1999 40 h.p. johnson run-away problem

Thanks Ezeke,
We did start the motor three times on ear muffs ,and the only way we stopped was to pull the line and try and choke it. What is decarberation ? Is it built up fuel in the cylinders and do you have a remedy?
Randy

 

[tashasdaddy]

Re: 1999 40 h.p. johnson run-away problem

randy to me it sounds like 1 of 2 things, the link and sinc is out from cleaning the carbs, see your manual. or the build up of carbon in the engine. do you troll a lot? here are 2 links on decarb:
http://www.boatsetup.com/Decarb_Carb.html

http://outdoorsbest.zeroforum.com/zerothread?id=2589

 

[ezeke]

Re: 1999 40 h.p. johnson run-away problem

I use the second method in this thread:

http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=36;gtid=1035563[/url][/url]

 

[DHPMARINE]

Re: 1999 40 h.p. johnson run-away problem

Also the motor may be overheating.Hot spots in the combustion chamber will keep firing the fuel.

Ain't kind of scary when it runs away ? Gets to me !!

DHP

 

[randy0050]

Re: 1999 40 h.p. johnson run-away problem

But the idle is so high that something will blow. Do I put it in the water on my trailer and put in in gear to stop the high revs? And then let try and burn the carbon out?

 

[ezeke]

Re: 1999 40 h.p. johnson run-away problem

If you can get the boat in the water, then buy a can of Mercury Power Tune and follow the instructions on the can. That should get rid of most of the carbon.

Be sure that you have a good water pump and thermostat as DHP has suggested.

Tashasdaddy's suggestion on the link and synch should not be ignored. Look down the carb throat while moving the throttle to be sure that the plates are moving correctly.

 

[randy0050]

Re: 1999 40 h.p. johnson run-away problem

The plates seem to be moving together, will cheak again .. I will try all that you guys suggested monday, have to work all weekend. Thanks for the time and effort . Will let you know .
Thanks again,
Randy

 

[randy0050]

Re: 1999 40 h.p. johnson run-away problem

one more thing? there are three lines leaving that pump. If one of the lines got crossed would it cause this type of prob.? I didn't put the pump on myself. Just thinking .
Take care,
R

 

[randy0050]

Re: 1999 40 h.p. johnson run-away problem

Thanks for the input !! Come to find out the fuel pump that looks self contained, is not as you more wise then i peaple know. It was never scewed back to the block (for testing puposes i suppose) therfore leaving the port behind it wide open, surrenduring the vacuum to pull all the fuel it needed to run it out of control( i am guessing) . Put screws and the gasket and it runs super, super great !! Thanks for all the help again guys !dd

 

[tashasdaddy]

Re: 1999 40 h.p. johnson run-away problem

glad to here you got it going. i had trouble trying to get one to idle, had left one of the plugs out.

 

[randy0050]

Re: 1999 40 h.p. johnson run-away problem

I hope ya cheacked the fuel first tashas !!! LOL Thanks for the help and take dare d

 

[randy0050]

Re: 1999 40 h.p. johnson run-away problem

I have read alot on this site and have learned alot. I hope you guys understand what a help you are. Peaple that are not very boat smart, get a boat for the first time, or find a problem that they just can't seen to figure out, you peaple take care of it !! I would just like to say thanks for the time and effort u put forth! Keep up the good work .
Randy