running on one cylinder

[journeyman]

I keep reading other posts trying to get ideas but i need help. I think I have two bad coils but not sure. I checked the resistance on the top two cylinders that aren't working and they are 153 and 150 which is up to spec.The one that works I couldn't get a resstance reading.The one that works goes to one cdi box and the two that don't work go to the other.I tried swithing the coils to the opposite box but then it wouldn't start.Thought it might be a bad trigger then,so I switched the connections for the two cdi boxes.It ran but still only on one cylinder the middle cylinder this time.Sorry forgot to mention I have a 1986 85hp force.Parts are expensive so I wanted to get some expert opinions before I go crazy buying parts.Please help Thanks.

 

[john from md]

Re: running on one cylinder

Coils rarely go bad. Usually your problem will be the CDI module, trigger or stator. I believe you can do resistance checks of the trigger and stator. To do voltage checks, you will need to buy a DVA adapter for your meter, $30 on line.

Have you cleaned all of the grounds to the coils and to the engine block? I would do that first. Next, if you have plugs and not a terminal board on the right side of the engine, I would clean them good and tie wrap them together. The get loose as the plastic shell shrinks with age.

Also, make your your plugs have a good ground when you do a spark check.

John

 

[journeyman]

Re: running on one cylinder

Thanks John I'll try cleaning the grounds. I did a resistance check of the trigger and it was up to spec. I'll try the stator.Can you get power out of one lead of the cdi and not the other

 

[john from md]

Re: running on one cylinder

Yes you can as they are two separate circuits. On the 85hp engines, you actually have a spare because there are only three cylinders. If the trigger ohms out good, chances are the problem is the CDI module.

There is a company called CDI repairs that is supposed to be the cheapest to buy from. You will have to google them as I don't have their url handy.

John

 

[journeyman]

Re: running on one cylinder

Thanks John you and so many others have helped me learn how to work on my boat since im new to boating.Ill look into getting a new cdi and get back to you later with the results Thanks again.

 

[john from md]

Re: running on one cylinder

No thanks needed, I feel like a father teaching his son to fish.

Please pass on what you learn to others when they have problems.

John