Re: 1991 25hp 2-stroke
Re: 1991 25hp 2-stroke
I have a similar issue on my 1989 20 HP merc (see my 7/15 3:00 p.m. post wherein I explain my problem in detail). I changed fuel, tanks, cleaned the carb. I did have different appearance on the sparksplugs (one clean and one oily) but had spark on both cylinders. I kept at it and then I only had spark on the top cylinder and not the bottom.
From what I have read this could be the caused by one of the fly wheel magnets coming lose and sticking to the other. Luckily you can check this without pulling the fly wheel. Mine are okay.
The other option is the power pack also known as the switch box (I think the one on your motor is the same as mine). You apparently can check the switch box using a peak voltage meeter also known in the marine world as a DVA. Should have voltage of 180 v or so. Most regular multimeters don't measure peak voltage. I don't have one so, before I went out and bought a new switch box I swaped the leads from the switch box to each of the coils and the problem changed cylinders (no spark on the top cylinder). Eureka . . . I thought. The next day I thought I would look at it all again, just to make sure before I spent $135-220 bucks on a switch box, and behold I had spark on both cylinders! I put the plugs in and it ran perfect (pull either plug and it would run rough but not die). So last weekend, I put the boat in the water and it started first pull and had full power. Yeah! Except I didn't do anything to fix it. We stopped on the other side of the lake and had a picnic, a couple hours later started it up on the way back and no power again!
Got back, I have spark on both cylinders. I am at a loss. I ordered a new switch box. I heard these regularly go out, so if this is not the problem, I have a spare. But all of this intermitten spark smells of an electrical issue. I will let you know when I get the part if this fixes my issue. Maybe you have the same.
