Johnson/Rude techs: Whats wrong with my 3cyl 70hp - WATCH video!

[swing]

All helpful ideas appreciated!!

FYI good treated gas:

http://www.youtube.com/watch?v=GgcSllZWm5A

 

[F_R]

Re: Johnson/Rude techs: Whats wrong with my 3cyl 70hp - WATCH video!

Check spark plugs. Check for a coil or plug wire arcing out to ground. Might be getting water in a cylinder (hope not).

 

[Dhadley]

Re: Johnson/Rude techs: Whats wrong with my 3cyl 70hp - WATCH video!

Describe "good treated gas". (We are talking about the fuel in the boat, right?)

 

[TruckDrivingFool]

Re: Johnson/Rude techs: Whats wrong with my 3cyl 70hp - WATCH video!

Does sound like its dropping a cylinder. Reminds me of my 50 before coils and a power pack.

I'd start simple by checking connections for tight and clean. Especially where the coil mounts if that's the ground. Then start testing components.

 

[HighTrim]

Re: Johnson/Rude techs: Whats wrong with my 3cyl 70hp - WATCH video!

Does it only do it at mid range?

I would start by running her when it is darker out with the cowl off to check for arcs.

 

[swing]

Re: Johnson/Rude techs: Whats wrong with my 3cyl 70hp - WATCH video!

Thanks so far- The regular gas is 5 week old (in the internal, clean steel, tank)... treated with K100MG ethanol//anti-sep/preservative.
Ran fine on same gas a month and a half earlier

One friend said to first "rule out" the fuel, internal tank, racor & copper fuel lines: by bypassing with a 3 gal portable tank with fresh 50:1
...havent done that yet, but a great idea!

Another said "I think its in the ignition somewhere: timer base, stator, a coil or powerpack...it is not skipping on all three cylinders


Any other thoughts?

 

[Bob_VT]

Re: Johnson/Rude techs: Whats wrong with my 3cyl 70hp - WATCH video!

Does it only do it at mid range?

I would start by running her when it is darker out with the cowl off to check for arcs.

Plus 1

or a coil going bad

 

[mudlake1]

Re: Johnson/Rude techs: Whats wrong with my 3cyl 70hp - WATCH video!

I would say its dropping a cylinder because of a spark issue.

It drops too quick to be a fuel problem to me.

maybe a coil or plug wire shorting to ground.

I have had spark plugs cut out like that as well.

 

[samo_ott]

Re: Johnson/Rude techs: Whats wrong with my 3cyl 70hp - WATCH video!

Does it only do it at mid range?

I would start by running her when it is darker out with the cowl off to check for arcs.

And if you use a spray bottle with water and mist it, it really shows the arcs

 

[swing]

Re: Johnson/Rude techs: Whats wrong with my 3cyl 70hp - WATCH video!

Its far more evident at midspeed.
High speed= barely noticeable, if at all
Low speed= seems mostly fine, except for a verry slight "shake" that wasnt there before.

Somehow I cant imagine running the boat right now in the dark, at 15 knots, with the lake level lowered, in 30 degree weather, leaning out over the transom with spray bottle mist flying right past the motor!

A local shop here ran it on muffs, checked all the wires physically, drained the carbs, inspected the gas, checked compression (learned theres at least one helicoil-fixed plug...prompting me to want to replace the old head cover with a fresh one!- a separate topic...or maybe related??) We didnt use a spray bottle, but it was a rainy day and high humidity- rain coming down just a couple feet past the motor (we pulled it into the repair shop garage bay so it was JUST inside- poor techs were getting rain spattering on their heads off the roof while fiddling with the motor).
They even filled a 55 gallon barrell to put a little more of a "load" on it, and we still couldnt see the problem. But as soon as i paid the 150 bucks for their time, and re-launched- well, thats when i took the video!

Long story short: on muffs: could not detect it at all, even when revved & speed held to listen/watch for it.
Only does it in the water/under a real load.
Why would that be??

Ran SO nice this summer, then this sudden skip

 

[HighTrim]

Re: Johnson/Rude techs: Whats wrong with my 3cyl 70hp - WATCH video!

Running on the muffs is not an indicator at all of a motors running abilitly, only shows that it will start. Once you put backpressure on the exhaust, that is when you truly test it. If I am going to spend any condsiderable amount of money on a boat/motor, I lake test it.

With that skip, I think simply by running her without the cowl on you may be able to see the arc at sunset. I wouldnt be leaning out over the transom by any means.

If you pulled the plugs after a run and did not find any water on them, I would bet you have a problem with the plugs, wires or coils. Ill assume you tried changing the plugs first before spending all the money at the shop?

 

[swing]

Re: Johnson/Rude techs: Whats wrong with my 3cyl 70hp - WATCH video!

Thanks Chris- Great points! I guess that some problems dont noticably manifest unless the motor is truly "loaded" and underway. And although there was no water on the plugs when pulled at the shop, and they looked good on visual inspection and we didnt change them...the truth is no: I didnt try changing plugs before swinging it by the shop....I didnt think it was a plug suddenly acting intermittent, and I wanted guys who know more to diagnose the motor "untouched"- fresh from acting up. (And im glad i didnt change em, because they had a hard time with a couple plugs- at least one had a helicoil, the bottom one was very hard to access, requiring angled tools i didnt own, and at least one needed cooling spray to break it free). So Im very inclned to change the cylinder cover and gasket with a nice, clean threaded one, new plugs too. MAYbe the problem will disappear then...but im thinking its a coil, a wire, or a weak ground. And i should check the condition of the stator under the flywheel while it getting work done....

 

[swing]

Re: Johnson/Rude techs: Whats wrong with my 3cyl 70hp - WATCH video!

I think we got it- at least this is the report from the marina:

It was one (possibly partially 2) of the (3) coils. Simply unscrewing & replacing them with new ones cleared it up. But it wasnt diagnosable in a tank or on muffs; motor had to be in the water and moving at midspeed- only then could process of elimination wire-swaps be done by the mechanic (AFTER repeatedly shutting off motor and re-starting each swap, to prevent shock!!)
Thanks West Cove Marina, New Milford...home of the Ever-rude team!