Mariner 25 HP Runs on one and no spark on other. Also what year?

[w32514]

Just bought a boat with a Mariner 25 HP. Took it out and it only runs on the top cylinder even after many minutes. When I got home I checked for spark on the lower cylinder and there was none. I then swapped the 12 volt wires to the coils and wires to plugs and it ran the same. I think this proves both coils are good.

So, what is my next step? I have skimmed here a bit and sounds like the black box (CDI?) failures are sort of common.

The CDI box has a part # 339-7452 A10 July 8 1988.

Mariner 25 S/N 0B397465

What year is this motor and was it made by Yamaha?

Thanks Much

 

[Laddies]

Re: Mariner 25 HP Runs on one and no spark on other. Also what year?

It's a 1989 and it almost has to be the switchbox or a coil as the statot and trigger act on both cyls on that engine, you can do a quick coil ck by swapping wires on the inputs to the coils

 

[w32514]

Re: Mariner 25 HP Runs on one and no spark on other. Also what year?

Already swapped intputs to coils and sparkplug wires and it ran the same, so that proves the coils.

I've read a bit about the switchbox and the triggers, cleaning the triggers, magnets, etc. Does that apply or is it all done with a single pickup as you said so if it runs on one then it has to be the switchbox? Is CDI the best brand switchbox?

Thanks.

 

[KIGuy52]

Re: Mariner 25 HP Runs on one and no spark on other. Also what year?

I replaced my switchbox with one from Bam Marine, (mercruiserparts.com). It was a Quicksilver (OEM) part. You might also want to replace the trigger if you don't mind removing the flywheel. They're made of cheap recycled simulated plastic substitute and the mounting ring cracks after a while, causing the trigger block to get caught in the flywheel magnets and get chewed up into a form of microscopic ignition trigger powder. Then a guy with a Yammy will pull you in, drink all your beer and talk about what pieces of crap Mercs are. At least that was my experience a few years ago.

 

[KIGuy52]

Re: Mariner 25 HP Runs on one and no spark on other. Also what year?

When you replace the switcbox, make sure the wires don't rub against the flywheel. I....uhhhh...had...uhhhh... a friend who made that mistake once and it made his motor run really bad. Luckily I was able to find the problem for him and routed his wires the correct way, paying particular attention to making sure the wires didn't touch the flywheel when the throttle was advanced fully. He was so happy, he bought me a 6-pack. Sadly, a short time later, his ignition trigger fell off.

 

[KIGuy52]

Re: Mariner 25 HP Runs on one and no spark on other. Also what year?

My list shows it as a 1993. Don't know if it's made by Yammy. Check and see if it has metric fasteners.

"Mariner 25HP - D182000-0D277999 - 1993 - Marathon"