Pinging issue

Motor?

 

My Merc 25-4 has done the same thing for 14 years. Cranking on the throttle it will ping; back off 1 mm and gone. Gotta be something other than internals so I live with it.

 

If it's a recent thing, maybe a drop in octane caused by too much ethanol in the last fill up? :-?

 

That is a possibility on FC's - mine has never seen ethanol (I am keeping it a secret from it).

But I don't think that is it Brett.  If you smash the throttle wot and then back off say 1 degree it quits.  It is such a small movement that it won't even affect rpm's.  It is strange but like I said I tried to find it but have lived with it and nothing has broke.

edit: almost seems like it might be the throttle cable. If turned too far it might create slack and slap around under the hood. Let off and the slack goes away. Just a guess.

 

Haha Tides bringin the funny!

Ethanol has nothing to do with the detonation. It is actually helping stop it.

My guess is that when your turning the handle all the way wot, your carb link is going wot but stops opening for that last 500rpms or so, but your timing arm is still advancing and that little area is where your detonating.
Honestly, its so finite i would almost have to blame it on how hot it is outside, combined with warm water temps, and the fact that you are a tad (my opinion) underpowered.
I wouldnt worry about it, just try to keep it out of that pinging area or youll have ashtrays for pistons..

 

Ha...believe it or not mine is actually ever so slightly louder in zero degree weather. It has a slight change in cadence and I can hear it more through my hats in that weather than I can driving naked in FL.

Cut - your guess is the same as my mechanic said but he was never able to find it even with adjusting some stuff. He even measured the amoumt the little arms would bend when you crank it all the way.

It has never been an issue so I left it. Besides, I get way better mileage when I back off WOT a little.

 

I don't think it's fuel related. It's it a ping or a spark knock? Where is it coming from the Cyc? or the Head? How many hours are on your motor? What Rpm's does it do it at? Did you put your old prop back on? and if so did it still do it? Does it do it every time?

 

No you would be able to tell if it hit the rev-limiter, skips not a knock or ping.

What year is the motor?

I had one last month I worked on 2009 F20 that only had 8 hrs on it. It was on a Ribbed Zodiac being used as a dingy for a 68' Sportfish. Anyways it had a knock at anything above 4800RPM's took me for every to figure it out. It ended up being a cracked piston skirt, motor ran fine and had no loss of power just a very faint knock. Not saying that's what yours is but with so little info it could be anything right now. Funny part is I still have the motor I called my client and he said by a new one, and gave me the old one. It's still laying in pecies out in my shop


Get an RPM's reading and also take the old prop just for the heck of it and throw it back on there and see if it does the same thing.

Standing by

 

At the time when the customer Purchased the engine it only came with a 3 year warranty you must have gotten yours during a promtion of 3+2. Trust me I keep track of all my clients warranties. However I called Yamaha dealer support because of the low hours and I did get them to pay for all the parts, customer pay on Labor (parts are still sitting in the box waiting on me). But my client said buy a new one! We upgraded to the F25 and it only has a 3 year warranty as well.

If your motor is under warranty take it in!!!

 

Could it be a plug not firing every time? I can hear a miss in a two stroke and not feel it, but a 4 stroke?

Frank_S