stinkynathan
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I have an early 80s Mariner 15hp (built by Yamaha). After last weekend's issues with top speed, it was suggested to me that ignition timing may be the reason I'm not getting optimal power/speed out of this motor. Armed with my tools and trusty Seloc manual I tried to at least tackle the static timing today so I could rent/borrow a light and finish everything next week when I get my TinyTach.
First, let me say that the Seloc manual is a horrible waste of paper. The directions tend to be pretty general and cryptic (to me, at least) and the pictures are horribly shot.
I ended up finally switching over to the Yamaha manual for this engine which I found on the Army's library online. I hope other service members realize they have access to these manuals online....
First, according to the directions in all books, there should be a triangle on the flywheel past 30* BTDC. The only mark past 30* is another tick which I assume is 35* BTDC. I'm also supposed to have a pointer on the magneto base and I don't. What I do have is a tiny tick mark which I can only assume is the pointer.
That said, when I'm trying to set the full-advance timing I run into a problem. I rotate the flywheel to 30* BTDC and set the magneto base to the "triangle" (35*?). I should be able to adjust the magneto stop bracket above the carb to touch the engine stop and it doesn't even come close. It's probably 0.50-0.75" away from the stop. If I set it as close as I can get it, I can't get the idle timing set properly because the adjustment screw isn't long enough to be adjusted properly.
Also, my Seloc says that full-advance timing is 22* and the Yamaha book I'm reading says it should be 30*. I'm not sure how either of those numbers affect what I'm doing, or if I will arrive at those numbers once I get a timing light on this thing, but the difference between them seems strange.
If you've timed older engines before or are familiar with the Mariner 15s I would appreciate any help you can give. Thanks!
First, let me say that the Seloc manual is a horrible waste of paper. The directions tend to be pretty general and cryptic (to me, at least) and the pictures are horribly shot.
I ended up finally switching over to the Yamaha manual for this engine which I found on the Army's library online. I hope other service members realize they have access to these manuals online....
First, according to the directions in all books, there should be a triangle on the flywheel past 30* BTDC. The only mark past 30* is another tick which I assume is 35* BTDC. I'm also supposed to have a pointer on the magneto base and I don't. What I do have is a tiny tick mark which I can only assume is the pointer.
That said, when I'm trying to set the full-advance timing I run into a problem. I rotate the flywheel to 30* BTDC and set the magneto base to the "triangle" (35*?). I should be able to adjust the magneto stop bracket above the carb to touch the engine stop and it doesn't even come close. It's probably 0.50-0.75" away from the stop. If I set it as close as I can get it, I can't get the idle timing set properly because the adjustment screw isn't long enough to be adjusted properly.
Also, my Seloc says that full-advance timing is 22* and the Yamaha book I'm reading says it should be 30*. I'm not sure how either of those numbers affect what I'm doing, or if I will arrive at those numbers once I get a timing light on this thing, but the difference between them seems strange.
If you've timed older engines before or are familiar with the Mariner 15s I would appreciate any help you can give. Thanks!
