power loss

[marclee]

I currently have a johnson 140hp (1987)loop type. The problem is that after about 40 mins of use it drops its power and sounds like it is running on 3 cylinders. I have checked for water in the fuel and have re done the carbies and checked for blockages. non of the above appear to be the problem.It mainly happens once motor is hot however it has occoured once when the engine was cold it would just not run properly. Can any body advise of a possible problem.

 

[R.Johnson]

Re: power loss

That could well be a coil acting up, but you are going to have to isolate the cylinder that is giving the problem. When it goes into this problem, pull one spark lead at a time to find that dead cylinder, and check the spark output to that cylinder. It all goes back to spark, fuel, compression.

 

[JB]

Re: power loss

Try this, Budda.<br /><br />Put her on the muffs and run her at idle with the hood off. (Do not rev without a load)<br /><br />Get a hair dryer and heat the powerpack(s)and coils, one part at a time. Heat each part as close as you can to operating temp after a hard run at WOT.<br /><br />If you are having a hot-failure (not uncommon in powerpacks. Less common in coils) you should drop one or two cylinders when you heat the right part. That is the part that needs replacing.<br /><br />Good luck.

 

[ob]

Re: power loss

I"m thinking you might be dropping ignition to one bank of cylinders but not sure whether your particular engine has one or two powerpacks.In any case ,try applying some artificial heat'ie' hair drier to the powerpack and around coils ,while running on the hose with engine cover removed,and see if you can simulate your power loss symptom.Sometimes those packs will experience warm engine failure.<br /><br />It would also be a good idea to simply perform a spark test on each cylinders lead ,and isure that at cranking speed with a fully charged battery,that each lead will jump a strong blue spark to ground of 7/16" to 1/2".

 

[marclee]

Re: power loss

Thanks to all for the information I will try and isolate the problem this week end and keep you posted on what I find Thanks again.

 

[marclee]

Re: power loss

Originally posted by ob:<br /> I"m thinking you might be dropping ignition to one bank of cylinders but not sure whether your particular engine has one or two powerpacks.In any case ,try applying some artificial heat'ie' hair drier to the powerpack and around coils ,while running on the hose with engine cover removed,and see if you can simulate your power loss symptom.Sometimes those packs will experience warm engine failure.<br /><br />It would also be a good idea to simply perform a spark test on each cylinders lead ,and isure that at cranking speed with a fully charged battery,that each lead will jump a strong blue spark to ground of 7/16" to 1/2".

 

[JB]

Re: power loss

Sorry 'bout that, ob. I must have been typing when you posted.<br /><br />Can't figure out why my post is dated 16 minutes earlier but appears after yours. Different time zone?

 

[ob]

Re: power loss

No worries JB.Heck I learned the method from you about the hair drier technique.Anyhoot,I've noticed that time glitch a couple of other times in the past.Strange thing huh.