Need Some Experienced Thoughts on a Johnson 90

[Pain'n'da'boat]

My question is: can spark plugs go bad from just sitting?
And could the carb need to be cleaned even though it was link & sync'd right before it sat?

Compression is 117 psi on all four pistons and replaced fuel line. Carb was link and sync'd and plugs changed 4-5 years ago used twice and then -it sat- and I am breathing life into her

At full speed (35 mph as per my speedo) it will be hauling butt and then it starts to die off, and then it will pick back up all on its own. Sometimes at WOT it doesn't want to go, it slowly starts to accelerate even though I have it almost to the floor-

Proud first time boater, brought my uncles old boat back to life and runs great except for the above mentioned--^

**EDIT
1981 Johnson 90 V4
16' Ebbtide Dynatrak
5100 RPM @ WOT (35mph)
19 pitch stainless prop
Pwr T/T

 

[bob johnson]

Re: Need Some Experienced Thoughts on a Johnson 90

I would look into the fuel delivery system..

when it starts to die at WOT squeeze the gas bulb and see if she picks right back up( rpms)

good luck

bob

 

[Pain'n'da'boat]

Re: Need Some Experienced Thoughts on a Johnson 90

I would look into the fuel delivery system..

when it starts to die at WOT squeeze the gas bulb and see if she picks right back up( rpms)

good luck

bob

Its kind of an intermittant issue, sometimes it runs smooth @wot, and other times when you give it full throttle it seems to almost bog down real hard, like its loaded up-?

When it starts to bog down I back off full throttle just a hair and it will speed back up (not smoothly) to top speed and then smooth out.

I will test the bulb both going fast and bogged down to see what it does...any other suggestions while im out? Are you convinced the plugs are ok still?

Thank you so much for your help!!

 

[Silvertip]

Re: Need Some Experienced Thoughts on a Johnson 90

Link & Sync has nothing to do with the possibility of the carbs being gunked up from sitting for a long period. Untreated fuel sitting in the carbs turns to varnish which is very likely the issue here. Running wide open with a lean engine is good way to burn it down. Thoroughly clean the carbs before doing anything else. If that doesn't help then pursue other potential issues. Every passage and jet needs to be squeaky clean. Since the boat sat so long, probably with old untreated fuel in the tank, the tank could also be gunked up so make sure thats clean and the fuel filters are changed.

 

[Daviet]

Re: Need Some Experienced Thoughts on a Johnson 90

I second a jet problem, pull the high speed jets, easy to do, and clean and blow out with air. If that cures the problem, tear carbs completey and clean all pasages, install new gaskets and your good to go.

 

[tashasdaddy]

Re: Need Some Experienced Thoughts on a Johnson 90

sure sounds like ethanol poisioning. agree with Silvertip.
http://forums.iboats.com/showthread.php?t=299680

 

[kenmyfam]

Re: Need Some Experienced Thoughts on a Johnson 90

I'm with the "clean the fuel system completely" group as well.
On another note. The motor has sat for a while. Change the impeller as well.

 

[Pain'n'da'boat]

Re: Need Some Experienced Thoughts on a Johnson 90

I didn't mention what I have already done to it before I took it out:

New impeller (old one wasn't that bad either)
new gear lube in lower end (no signs of water or metal shavings)
drained gas tank and flushed (gas still looked brand new and the bottom of the tank was clear of any sludge)
replaced fuel line from tank to motor and squeeze bulb
ran compression check on all cylinders

also I was told it is always ran out of gas after each use which I continue to do....is this a good idea?

didn't replace spark plugs though-

I will remove the jets and blow them out before I take it out tomorrow and see...I am leaving for Inks Lake State Park @ 4:30 am to see if I can't Texas Jig me out some big bass-

You guys are awesome and I think it is a blessing that this forum exists!

 

[iwombat]

Re: Need Some Experienced Thoughts on a Johnson 90

Do NOT run it out of gas after each use.

This is a multi-carb'd 2-stroke. One carb will dry up first (the top). The cylinders it feeds will be running w/o lube until the other one dries up.

Instead, make a habit of using fuel stabilizer.