Engine intermittently loses top end power

[JeepinAndy]

Hi All,
I have a 16ft 1972 Mirrocraft with a 1973 Johnson 65 HP motor model #65ESL-73R.

Lately I have been taking it out on the lakes and it has been very difficult to start the first time - however it always starts after 15-20 seconds of constant cranking the 4th or 5th time and starts right up on all subsequent starts.

But also what has been happening is that it runs great for 20 minutes or so and then if I shut it off and start it back up (starts on the first 1/2 crank at this point) it gets to about mid throttle and just starts to bog and crap out. It will surge and sometimes if I throttle it back and then open it wide it goes full out for a second then starts to bog and run crappy - it never dies.

I looked at the choke butterflys and they look wide open and the fuel line hose is fairly new, there are no fuel leaks that I can see and I took apart the fuel filter and pump; everything is clean and looks good.

Anyone have any ideas? I am new to outboards but savvy with car engines, carbs and electrical work.

Any help or troubleshooting pointers would be greatly appreciated.

Thanks,
Andy

 

[tashasdaddy]

Re: Engine intermittently loses top end power

check your spark on all 3 cylinders when it does this. may have a coil failing.

 

[kenmyfam]

Re: Engine intermittently loses top end power

Agree with the coil thing. Could have a suspect one.

 

[JeepinAndy]

Re: Engine intermittently loses top end power

OK thanks I will check the coils out. I did listen to see if the coils were clicking or making any "shorting" noises and did not hear anything. But I guess they can be faulty and silent.

 

[kenmyfam]

Re: Engine intermittently loses top end power

Spark check will let you know which cylinder.