91 evinrude miss

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maxtor2003

Recruit
Joined
May 14, 2008
Messages
5
Ok just bought this 91 evinrude and problem is driving me mad...

idles and starts perfect............. WOT is perfect

at 50% throttle misses bad........... almost like gets no spark at all for a second then resumes ........ moreless cuts in and out.

seller said carbs were rebuilt lastyear to try to solve this issue........

Did compression check and both are same (123) if i remember correctly.

Did this with bran new plugs aswell. (seller said he tried new plugs but didnt solve)

I took out both plugs and they were wet and appeared to have oil on them.

gas mixture is correct...

Any ideas?????
 
C

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: 91 evinrude miss

Need more info

It's a 91, a twin, runs sick at half throttle

make and model would be helpful

When it is acting strange, at half throttle, have you tried pumping the primer buld to see if that has any effect.

Can you 'bump' the choke or enrichener for a heartbeat and see if that has any effect, good or bad.

You may install an in-line neon spark tester and watch to see if yoou have a miss fire or no-spark at that spot in the throttle,, possibly a shorted wire in the timer base.
 
M

mikesea

Lieutenant Commander
Joined
Oct 1, 2006
Messages
1,830
Re: 91 evinrude miss

under the flywheel is a timer base,it will be connected to the throttle with a little metal arm.the arm snaps into place by a ball and socket made of plastic.Make sure it is connected on both ends,they go bad cause the plastic get brittle,make sure the timerbase moves smoothly as throttle is advanced,
 
M

maxtor2003

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Joined
May 14, 2008
Messages
5
Re: 91 evinrude miss

ok ......
Installed a carb kit today.........and new plugs...

Found out its actually a 1989

Took for a test run and to my great disapointment ...............still does it :(

I have tried pumping the ball and choking it.........neither make a difference.


Im almost positive its losing spark.

How many turns should the main needle be out? (one inside larger brass cylinder) When i turn this it seems to slighty effect it but not much.

Ill take a look at the timer base. I noticed when looking at it before it seems to have play in it. Is that normal?

Thanks for the help :)
 
M

maxtor2003

Recruit
Joined
May 14, 2008
Messages
5
Re: 91 evinrude miss

What its doing is when im running and just before boat starts to plane..... say at 1/2 half throtle the motor will cough ..........and jerks...... loses rpm then comes back to life and repeats............ about 10 - 15 seconds between. When it coughs or cuts out it only lasts for a split second.

Problem is driving me mad :mad::confused:
 
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