20hp blue band

Hi guys,

I got a dirty old 20hp blue band that I have restored, took it out for its first run last weekend, everything went great, didn't miss a beat then all of the sudden it made a loud "chuff" noise and shut off. I tried restarting it but wouldn't start. The motor turns over, is getting spark and fuel but sounds like the timing has gone out all of the sudden with the "chuffing" noise it makes when you turn it over. The timing linkages aren't loose at all so I cant see it being timing. I have been told that if the key breaks off in the keyway it can cause timing issues, so I pulled it all apart but the key is fine.

Can anyone give me some hints before I bite the bullet and take it to a mechanic. :facepalm:

Thanks guys.

Re: 20hp blue band

Did you hit something with your prop/lower unit when it happened? You may have and not known it. That reaction is exactly what happens when you shear the flywheel locating Woodruff key and you ainta-gonn-get-r runnin till you replace it. BTDT.

That key has to be in perfect condition for the timing to work properly, not sheared, and not even marked up (partially sheared) from a previous incident.

Mark

Re: 20hp blue band

Thanks for the reply, I have pulled it all apart and the key is still in perfect condition.

Re: 20hp blue band

With that 'chuffing' sound you didn't suck a reed valve did you?

Re: 20hp blue band

Possibly. I'm not to familiar with 2 strokes, how do I check the reed valves?

Re: 20hp blue band

I can't say. Never owned a 20 Merc to work on one. The reed are in there between the caruretor and the block. Plenty of others here will be able to tell you. Or, if you got a manual it'll be in there.

I have had it happen to me on a couple of Johnsons, an 18 and a 25. Both times going down the lake wide open and then I noticed as you say a 'chuffing' sound and extreme loss of RPM.

Re: 20hp blue band

Thanks mate, I'll rip the carby off and sus it out.