1989 evinrude 48 spl surging above 3000 rpm

[69starcraft]

I bought an 89 sunbird with a 1989 evinrude 48 special.

wouldn't run when I got it (hence the good deal) so I did a thorough carb clean and she fired up and ran like a champ. took it to the lake two seperate occaisions and had no issues

3rd time on the lake, as we were coming home from it running beautifully all day it started surging badly. We were on plane at WOT and suddenly it started surging between 3000-5000 rpm

Found that squeezing ball didn't help. Also noticed that if I kept it at 2000 rpm it would idle just fine, and we limped home the scenic way

got home, pulled and checked both carbs again...they are clean as a whistle. Verified compression at 150+ on both cylinders, spark plugs are new and not fouled.

Put everything back together and tested on lake again....once again idles fine, but as soon as you get on plane it starts to surge wildly again

I'm thinking fuel restriction....but my carbs are cleaner than most of the boats I've ever owned... i can't find anything wrong...I am a mechanic too btw

fuel pump is working...verified by priming and then turning over starter with lines disconnected and I am getting healthy spurts with the pump

any ideas??

 

[Daviet]

Re: 1989 evinrude 48 spl surging above 3000 rpm

Did you check the high speed jets for any restrictions?

 

[69starcraft]

Re: 1989 evinrude 48 spl surging above 3000 rpm

Jets are clear...could eat dinner out of them the carbs are so clean

they weren't even "dirty to begin with.....I have seen/fixed worse

 

[Daviet]

Re: 1989 evinrude 48 spl surging above 3000 rpm

Use an inductive timing light when the problem happens and see if you are dropping a cylinder, if not it has to have a fuel delivery problem.

 

[69starcraft]

Re: 1989 evinrude 48 spl surging above 3000 rpm

Use an inductive timing light when the problem happens and see if you are dropping a cylinder, if not it has to have a fuel delivery problem.

dropping a cylinder?

 

[69starcraft]

Re: 1989 evinrude 48 spl surging above 3000 rpm

also, just finished breaking down and checking the carbs for a third time....nothing out of the ordinary I can find

electrical maybe, but it idles below 2000 perfectly..

ran the cold idle lever up to about 3500 (engine submerged in barrel, not flush cuffs) and its running a bit raggedy....not as smooth as i would like

would bad coil only present at wot throttle and still idle perfectly...not hard to start. not hard to start cold...just won't go

dave

 

[Daviet]

Re: 1989 evinrude 48 spl surging above 3000 rpm

Sorry, loosing spark to one cylinder.

 

[sdanville]

Re: 1989 evinrude 48 spl surging above 3000 rpm

69starcraft - - -

So, what happened ?

Did you find the cause ?

Electrical ?