Does this merc sound right? Popping sounds? *video*

[erikpn]

This guy wants to sell me this 7.5 merc for $400. I'm sure he warmed it up before making the vid, but what is with the popping sound at idle towards the end of the video? A misfiring cylinder?

http://tinypic.com/r/fm2vwi/6

 

[cbavier]

Re: Does this merc sound right? Popping sounds? *video*

Doesn't sound right to me. Run don't walk. Something is wrong here. That's probably why he wants to sell it. Somebody else will chime in here soon.

 

[ENSIGN]

Re: Does this merc sound right? Popping sounds? *video*

Sounds like a miss.If he warmed it up as you said,Why so smokey?Cover your A##

 

[Bubbles Up]

Re: Does this merc sound right? Popping sounds? *video*

I have a 78 Merc 7.5 mine would make a popping sound similar as my wires to the kill switch were in bad shape. I could pick the insulation off with my finger nail ,so I figured I had a "leak" to ground.I swapped the wires and a new monetary contact switch. For the switch I used a push button engine start switch(industrial style) with the water proof cover,for wires the local auto parts store had the orange and the black (#14AWG) I needed.As an extra measure I shielded the wires in a clear teflon tubing.A couple of crimp lugs and some water tight heat shrink to the wire/teflon coating. Looks factory andI am into the new switch for a whoppin $12.50 total! Compare that to the $65 that the dealer wanted.

Give the engine a good look over and maybe even take the guy on the water for a sea trial of the brown band (mid 80`s ) to test performance.
Or use the popping sound as a bargaining tool,"Well that popping sound........(insert BS here).... What do you say to $2XX -$3XX?

 

[Tig]

Re: Does this merc sound right? Popping sounds? *video*

+1 on the miss. It misses, loads up on raw fuel a touch, then fires rich. Which would explain the excessive smoke.
It probably will not troll well until this is resolved. My 1966 Evinrude 33 misses like that at idle. I can smooth out the idle by richening the mixture. Trolls very nice then, until it carbons up, then I'm stranded.
If it runs fine at speed it could be as simple as carb cleaning or not. If it still breaks down at speed it may be the magneto breaking down.
If a compression test was good I would negotiate for it.
If you are up to tuning, it could be a good deal. If you have to pay a shop then it's an unknown.....
Just my .02

 

[hkeiner]

Re: Does this merc sound right? Popping sounds? *video*

If the compression on all cylinders check out OK and you confirm that there is no water leak into the lower unit oil, then you probably won't risk a costly mistake getting this motor... as long as you can do your own tune up and troubleshooting work. On the other hand if you have everthing done by a shop, buying an older motor that does not run well from the get go can become a costly decision. Just my thoughts.

 

[Smokepole27]

Re: Does this merc sound right? Popping sounds? *video*

Is this common with mercs around that year model??? My buddy bought a flat with a 25 on it and is haveing the same exact problem like a knocking noise at idle but goes away when you give it throttle.....

 

[199675hpforce]

Re: Does this merc sound right? Popping sounds? *video*

What lol sounds good to me? If the sound playback is anything like the cheap cammera being used well there you go.

 

[Barnacle_Bill]

Re: Does this merc sound right? Popping sounds? *video*

Sounded like it's idling too low.

 

[SuzukiChopper]

Re: Does this merc sound right? Popping sounds? *video*

Sounded like it's idling too low.

This was my thought too. Idling so low it's barely running.

 

[JBS141]

Re: Does this merc sound right? Popping sounds? *video*

I own a 7.5 mercury and the reason for the popping noise is
because the idling/fuel mixture screw on the carb needs to be set a little lean.
sound like its running too rich! any ways very easy fix! and for 400 bucks
thats a good deal for one that new! I would get it if I where you!!
these are Great little motors!!