1971 Evinrude 50hp weak spark

[expertsetup]

Hello everyone,<br /><br />I have a 1971 Evinrude 50hp Lark. My lower unit shifts great and I have had this motor out for a run where it ran at 5500rpm and moved my 16'2" boat at 33mph with three full grown ~180lb men aboard.<br /><br />The compression as of yesterday is:<br />cyl 1 125-130<br />cyl 2 125<br /><br />WHen I took this boat to the lake and went for a test run after it being stored for 6 months or more I had a heck of a time starting it. Once it did start it ideled right up to 5500rmp no problems. As soon as I engage the lower unit and put a load on the motor it droped to 2500rpm and would move the boat at about 6.3mph.<br /><br />A quick look under the cowl showed the fuel pump pumping fuel out of a screw hole. Reparing the fuel pump took a few minutes but didnt help the problem. After reviewing the manual troubleshooter guide and reading several posts on this website I decided to go back to basics.<br /><br />I took a compressino test and spark test. Here is what I found. The top plug generates a deep blue spark that jumps across a 1/2" gap like a gymnist. <br /><br />The second (lower) plug produces a redish orange spark that seems to want a 1/8" gap or less for it to jump. I suspect the coil as it appears to be the original unit. The lead is loose and seems like it is poorly attached to the coil.<br /><br />My question is, since all I have is a digital meter the power pack test might not work right for me as it requires needle jump watching. Can I simply swap the coil leads to the power pack to determin if it is the coil and not the power pack?<br /><br />Thanks again,<br />Expertsetup

 

[angus63]

Re: 1971 Evinrude 50hp weak spark

If the coils are identical, swap the coils to find the source of the issue. Also, do not "idle" in neutral above 2k RPM or the motor may run away and turn ballistic !!! Just swapping leads will put her out of time.

 

[fireman57]

Re: 1971 Evinrude 50hp weak spark

If the orange spark follows the coil then suspect a bad/weak one and replace.

 

[expertsetup]

Re: 1971 Evinrude 50hp weak spark

Hi angus63,<br />I should have said that when in nutral I can rev it up to 5500RPM it idles @ less than 2000 but rough lower than 1500RPM due to the bad spark I would assume.<br /><br />I will be sure to change the coil connections to the power pack and to the plugs both. I will be sure to let you know the results, my lunch break is at noon and I cant wait to solve this problem. Should know the results after I return in a few hours.<br /><br />Hi fireman57,<br />I have made a call to NAPA (there is one right on my block at work) and the new coil is only $32. Since this one is so old and crummy looking I decided to order it anyway, as well as a new diaphram kit for the fuel pump. I suspect it will follow the coil.<br /><br /><br />Hope the power pack isn't bad as that may be quite a bit more expensive.

 

[Paul Moir]

Re: 1971 Evinrude 50hp weak spark

expertsetup - heed angus63's advice. There's few worse things you can do to a 2-stroke then rev it up in neutral. Besides, it doesn't tell you anything at all.

 

[expertsetup]

Re: 1971 Evinrude 50hp weak spark

Hello again,<br /><br />Thanks Paul and angus63 for the advice about reving it in neutral. I thought everyone might think I had my idle set to 5500RPM. I am quite green at this outboard stuff so I will be sure to heed this advice and not rev it out in neutral.<br /><br />I have returned from my lunch break and when I swaped the coils connections to the power pack the story was complete. It is in fact the coil as the working coil does fine on the second channel on the power pack.<br /><br />Cant wait to get the parts and take her out on the water again.

 

[angus63]

Re: 1971 Evinrude 50hp weak spark

Be sure the grounds are clean and tight on those coils. Good news it is a simple coil replacement. Enjoy the water!!!!! (I'm still shoveling snow off of my cover....)<br />Good luck