2001. Yamaha Getol 2t 50HP

[Goran_SV]

First of all, let me say hi to you all

For some time now I have a 2001. Yamaha Getol 2T 50 HP. Everything worked fine, and I did the usual maintenance (oil, impeller, spark plugs...). Every time with original parts, or parts that Yamaha suggested.

Few months ago spark plugs started (NGK ones) to behave badly, so I replaced them. Unfortunately, I didn't get the ''original'' NGK B8HS-10 as manufacturers suggests, but Champion L87YC instead. They were the only available at that time, and seller told me that's kinda the same. Ah, well... I used those.

For about 4 months everything ran smoothly, until few weeks ago. The engine just wouldn't go over 2000 RPM. I thought it was because of bad sparks, so I replaced them with new ones, again with those Champion - and yes, again they were the only ones i could get in a short amount of time

The problem persisted. Ah, yes... from time to time, when I push throttle very fast, engine goes over 2000 RPM, and runs smoothly... until I decrease the throttle, then it starts to work badly. Basically, 1 cylinder won't work. Sometimes it won't work at all, sometimes it works for some amount of time (until the throttle is reduced). The same happens while I drive, and when I stay still.

I tried to clear spark plugs, all connections that could be malfunctioning (wires, connectors, spark plug caps)... but the problem is still here.

Finally, i managed to get some info on those Champion spark plugs... and it seems they are ''replacement'' for NGK B7HS-10, and not B8HS-10.

Could that be the problem? Because friends started to scare me with ideas that C.D.I. unit is broken, or stuff like that

[boats.net]

Thats a hotter plug, need to get correct spark plugs. Start with a compression test, check for spark when rpm's drop, check fuel and carbs.

[Goran_SV]

Thank You for Your answer... I really hope it isn't the C.D.I. unit, since it's round 1650 US dollars in my country, at authorized dealer

Is there any ''smarter'' way to test for sparks other than unplugging spark plugs (removing spark plug caps) on at the time while the engine runs in N (neutral)... With that method, if I'm lucky, I could find the non-working cylinder at first attempt... or maybe from third attempt.

can that method do some damage, and is there any other?

[boats.net]

Use a timing light to see if loosing fire while engine is running.
Don't know what model you have but find part number of CDI and check the price of parts here on this web site, Boats.net - New and Used Boats for Sale, Outboard Boat Motors, and Discount Outboard Boat Parts.

[99yam40]

Spark testers are sold at automotive part stores and online if you do not have a timing light

[Goran_SV]

Checked some parts prices, and I can say just one thing:''OMG!!!''

For example:
- C.D.I. unit assy 461.46$, in my country round 1685$
- Ignition coil assy 76.25$, in my country round 139$
- relay assy (for triming) 157.69$, in my country round 391$
- and so on... you got the idea

Anyway, there's no use of ''crying over my destiny''... so, I guess even that ''instrument'' you suggest for checking sparks will cost a lot... not to mention probably hard to get.

So... for the first step, should I pull the spark cable while the motor is running, when I try to turn it over 2000 RPM and it starts to work badly... or can I pull it before I even start it... and by that method diagnose which cylinder is not working?