poor performance@high r.p.m

A

Aric

Recruit
Joined
Sep 15, 2002
Messages
3
I have a 1991'Johnson 200GT(V6,loopcharged)and it misses and runs poorly at higher r.p.m.Sometimes it will run w/o any problems at all,observed mostly at50-60 mph and when fully trimmed.Idles well! replaced spark plugs and problem still arises.In April 2001 a new fuel pump and all 6 carb. kits were replaced because the boat had been sitting for 3yrs.
 
D

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: poor performance@high r.p.m

Give us more info. What spark plugs? And be SPECIFIC!!! What rpm's? If it's missing at wot, does it straighten out if you back off the throttle slightly?<br /><br />Let us know!
 
A

Aric

Recruit
Joined
Sep 15, 2002
Messages
3
Re: poor performance@high r.p.m

the plugs are Champion QL78YC and Im not sure of the specific r.p.m at which it occurs.It seems to perform well at half throttle, but when you increase it slowly to higher r.p.m it will start cutting out and missing,although it can recover by backing off the throttle just a bit or shoving it to full throttle. The problem is so hit and miss that it leaves me puzzled??? could it be fuel filter,oil-fuel ratio,vacuum?????
 
A

Aric

Recruit
Joined
Sep 15, 2002
Messages
3
Re: poor performance@high r.p.m

the plugs are Champion QL78YC and Im not sure of the specific r.p.m at which it occurs.It seems to perform well at half throttle, but when you increase it slowly to higher r.p.m it will start cutting out and missing,although it can recover by backing off the throttle just a bit or shoving it to full throttle. The problem is so hit and miss that it leaves me puzzled??? could it be fuel filter,oil-fuel ratio,vacuum?????
 
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