Powerpack problem on 1975 115 Johnson

[crb478]

I have a 1975 Johnson 115 that I am having trouble getting dialed in. I believe that I have an intermittent problem with the power pack. I have also had to swap out a couple of coils to get all four to work. I just got back from the water where the boat was not running on all of the cylinders. It was running on all cylinders at home on the hose before I drove to the ramp about a mile away.

I brought it back to the house and put it on a hose and it fired right up, but the #1 and #3 cylinder were not firing. I took the power pack off and swapped it with an unknown used one that I had and only cylinders 1 and 2 were firing. I put the origional power pack back on leaving the cover off and it was firing on all four cylinders. I cut the boat off and put the power pack cover back on and when I cranked it there was not any spark to cylinder 1 or 3 again. I loosened the power pack cover screws on the starboard side and the engine reved up and I again had spark on all four cylinders. I tightened the cover back down and it continued to run on all four cylinders.

I cut the boat off and put a double gasket under the power pack cover, and it still is running on all four, at least right now! I used a conductive timing light to verify spark each time. I did also notice that cylinder number 3 has an intermittent spark. It will probably fail to spark once out of every 100 -200 revolutions when on the hose. I hope to get it back to the water today, but might not have time.

I don't want to buy another power pack if that is not the problem. I would appreciate any advise on trouble shooting this problem. I can take the boat out one time and get it up to about 48-4900 rpm then the next time it will only fire on part of the cylinders and not go over 2000 rpm. I feel that even when it is running that it is not putting out full power.

Also the spark will jump a 7/16 inch gap, but it looks more yellow than blue to me. Compression is between 110 and 125 for all four and the carbs have been rebuilt. Does anyone feel this could be a stator problem? Has anyone ever heard of a power pack cover intefering with delivering spark. I have removed the cover a couple of times and had the motor run correctly again. Thanks for any help, Carl

 

[tashasdaddy]

Re: Powerpack problem on 1975 115 Johnson

take a look at this. http://www.boatpartstore.com/page30.asp

 

[crb478]

Re: Powerpack problem on 1975 115 Johnson

Thanks Tasha's Daddy I was looking for that earlier and could not find it. I will have to see if I can borrow a DV adapter.

 

[ezeke]

Re: Powerpack problem on 1975 115 Johnson

There were numerous problems with the powerpack because of placement and sealing.

One situation covered by a service bulletin was that when the motor was tilted up, the water ran through the grip on the engine cover and dripped directly on the powerpack. Another came from carbon traces left on the gasket. The later powerpacks came with rubber gaskets to seal the powerpack and liquid tape was used to waterproof the screws and terminals.

Another problem was the rack that holds the ignition components is not well grounded so that grounding straps were required. It is particularly important that the wiring and the contact points be well cleaned to provide excellent connectivity. Unfortunately, you have to take everything loose to clean.

 

[crb478]

Re: Powerpack problem on 1975 115 Johnson

Thanks Ezeke,

I suspect that that is part of what is going on with mine. I doubled up on the rubber gasket when I put it back together. I took the boat out late yesterday and had spark on all four cylinders. I then made a WOT run and got it up to 5200 rpm where it had been at 48-4900 before. Carbon arching sounds like it may have been part of the problem. I will clean the gasket better and then reasemble it. I also cleaned and doubled up on most of the grounds before I took it out. Ran new spearate grounds to all the coils bolting them directly to the engine block. I may add yet another ground to the power pack itself as it is it only grounds to the mounting screw which goes to the rack. Thanks Again. Hopefully this will fix it for a while

 

[crb478]

Re: Powerpack problem on 1975 115 Johnson

Thanks again Ezeke!

When I got home today I took the power pack cover off and grounded the power pack lead directly to the exhaust cover and then jumpered from there to the rack. I also washed the power pack gasket as it had a light build up inside of it, I guess that this was carbon. I made sure that all the grounds were clean especially the #3 coil which was the one that had intermitten spark. I then put everything back together.
I cranked the engine up and put the inductive timing light on the number three plug wire and the intermitten spark was gone. It is running like it should, at least for now. Hopefully I can get it out on the water in the next few days and see if I can pick up a few more rpm's at wot.