1972 Johnson 65HP bogging, slow to make RPM

[sbklf]

No trouble with my 65HP till last weekend. It starts and idles OK and even revs OK in neutral but is a real dog taking off. It will finally get up to about 4700 rpm (it would always make 5500 before) after a 1/2 mile or so but I can tell it has more. I cheked the choke selector OK and I verified the choke is releasing, pump ball pumps up and stays hard, new plugs, fresh gas, when it does get up to speed it does not smoke like it is loaded up or miss.

Any ideas?

 

[bigpoppakdog]

Re: 1972 Johnson 65HP bogging, slow to make RPM

oh lets go with the usual:

1. Carbs cleaned recently? Redone carbs recently?
2. compression test? I had a chrysler motor that had a cylinder with 40 lbs of compression. Would take a while to get going, but eventually would pick up speed..
3. Idle adjustment needed? Did you try pumping the bulb during takeoff?

I don't know, did I miss anything else?

 

[jay_merrill]

Re: 1972 Johnson 65HP bogging, slow to make RPM

Test the ignition on each cylinder with an inductive timing light - you might have a cylinder that isn't firing. You could also have a carb that has picked up some junk in one of the high speed needle valves. I had the same problem with my '72 J65 - it drove me crazy because I ended up having both problems!

The fuel side of it drove me nuts because I have a fuel/water separator & filter, plus I knew that the fuel pump had a screen in it. Regardless, I found what looked like a piece of white plastic in the bottom carb. Where it came from I have no idea, because the fuel pump was not failing. The photo below shows what I did to prevent anything else from getting in the carbs via the fuel delivery system.

 

[sbklf]

Re: 1972 Johnson 65HP bogging, slow to make RPM

Man this forum is busy, thanks for the tips Big and Jay, I will work on it this weekend and post the result.

 

[sbklf]

Re: 1972 Johnson 65HP bogging, slow to make RPM

It appears to be a bad sensor coil, #1 plug is not firing and the resistance reading across #1 sensor coil is almost infinite. How much can I expect to pay for the coil assembly or whatever it is I will have to purchase to replace it?