No spark on one cylinder

[croixflats]

Help needed.

Yamaha ProV 150

Last couple of times out going across the river at top speed the motor would lose power from 55mph to 45 mph and would be sluggish out of the whole. This would happen spur addict, now I have lost power permanently.

Put 2 new fuel pumps in and full set of new spark plugs in. Today I checked spark plugs and all plugs were chocolate brown except for 1 witch were clean like new. So now I assume that one of the CDI boxes(I assume these are individual coils for each cylinder) went bad. Anybody know how to test these. Or could there be something else wrong.

Any help would be greatly appreciated

[Valv]

If you have individual coils, switch one over with the "bad" one. If it fires and the other not it is the coil.

[boatfixer]

croix, you have mail

[croixflats]

Thanks Valv and boatfixer this helps a whole lot! I realy do appreciate the help.

When I lost power I thought I might have melted a piston, been there done that. Never thought I would be happy with an electrical problem.

Now that is darker out, so I can see spark better, I'm going out now to try the sugestions.

[croixflats]

Baffeling, checked the spark and all seems fine. I'll puts with it tomarrow. Ive got to go pick up a new ohm meter and a compresion tester. Maybe the bad coil decided to work again being it seemed to be intermitant. I see no other explanation behind a clean spark plug.

[sparcebag]

sometimes a coil will fail only when warm and it expands

[croixflats]

Thanks sparcebag good thing to keep in mind. I guess I'll put the muffs on and warm it up to see if I can get it to fail or put it in the water. Dealers are closed till Monday so I'll have to wait to go fishing. I hope I dont get sucked into watching the vikes being I'm not on the water.

[Valv]

Do a compression test before you take it to the dealer....

[croixflats]

Compression test came up strong, same in all cylinders

After reading the trouble shooting manual boatfixer emailed me it looks as though 1 of 3 things. Stator,switch box or coil.

I havn't got access to a good dva meter and that I couldn't tell the difference between a stator and a switch box let alone locate them so I'm going to bring it to the guy who rebuilt the engine a few years back he does great work and is affiliated to a local marine dearlership and shop.

[boatfixer]

It more than likely is not the stator, that is common to all cylinders. CD module, coil, coil wire, plug wire can affect 1 cylinder at a time.

[croixflats]

Yea, that makes sence. I only hope its not the CDI box and its something small like a wire or a coil. If its the CDI box it will have to wait till next year because the rest of my big purchases are going to hard water this year.