25 hp Evinrude Bad Cylinder?

[krampuppy]

Ok heres the deal....<br /><br />I have a 1957 (I think) 25 hp Evinrude. Today it started to miss at full speed. It runs fine at idle... but when I throttle up it will only run a little bit faster than idle speed. I replaced the plugs... that wasn't the problem. After a lot of messing around I found that when I pull the top spark plug wire the motor kills. The bottom wire is providing spark as it shocked the crap out of me when I tested it. Does this mean the cylinder is bad or is the carb gummed? Does anybody have any ideas as to what I should do next? I don't have a clue.... any help would be appreciated... Thanks

 

[Hooty]

Re: 25 hp Evinrude Bad Cylinder?

Ok, here's the other deal. <br />First, ya need a repair manual for that thang. It sounds like it's only hitting on the top cylinder. It ain't the plugs so the next thing I'd do is a compression check. If that looks ok, then clean the carburetor and put a kit in it. You'll need the manual for that. Let us know what happens.<br /><br />g'luck & c/6<br /><br />Hooty

 

[OBJ]

Re: 25 hp Evinrude Bad Cylinder?

Hi kram....<br /><br />No it don't mean the cylinder is bad. Try and swap the spark plugs. If the situation reverses...then the spark plug is bad.<br /><br />Could you please post the model number of the engine? Don't think it's a 25 from 57'. Thanks!

 

[krampuppy]

Re: 25 hp Evinrude Bad Cylinder?

I checked the compression it is okay... I tried switching the spark plugs that wasn't the problem either... So it must either be a bad cylinder or a gummed up carb. Can anyone tell me how hard it is to clean the carb and put a kit in? Also, where would I find a manual for this old boy. The Serial # is: 25920-17747. There was no model number listed that I could find. Any help would be greatly appreciated.<br /><br />Thanks

 

[krampuppy]

Re: 25 hp Evinrude Bad Cylinder?

any ideas?

 

[krampuppy]

Re: 25 hp Evinrude Bad Cylinder?

Just putting this back at the top of the board looking for a response thanks

 

[Paul Moir]

Re: 25 hp Evinrude Bad Cylinder?

Double check the bottom spark. It should jump 7/16" (keep your fingers away when you do!). If it's not strong, it will not ignite the mixture at higher rpms. Compare it against the top spark. The top and bottom systems are almost completely independant of each other.<br />The problem could conceivably be a blocked main jet in the carb, but that's rather unlikely. That is unless the high speed mixture screw not set correctly.

 

[Cricket Too]

Re: 25 hp Evinrude Bad Cylinder?

Kram....I'm not sure what you mean when you say a bad cylinder since you said the compression was good, but anyway if I were you I would tear down those carbs, clean them and put a kit in them. It can't hurt and it may well be your problem, a manual will show you how. Good Luck.

 

[Hooty]

Re: 25 hp Evinrude Bad Cylinder?

That's a 1955 25hp, Krampuppy and if you click on the "Repair Manuals" icon in the lower lefthand corner of this page, they'll fix ya up.<br /><br />g'luck & c/6<br /><br />Hooty