1986 evinrude 120 surging

[glenn property of pam]

went fishing today. motor started first go with a little choke then we ran 10 mins in no wake zone. went to power up on plane and motor seemed week and stuttery (2-3 seconds) then came up to full power and the boat got on plane no problem. back throttle to 4200 rpm and trimed then the motor suddenly seemed to gain 400 rpm and alot more power then 10 seconds later loss 400 rpm and power. it seemed to be doing it every 10 - 20 seconds. if i throttled up to 5200 rpm it seemed more stable. after stopping and fishing for a bit we moved on and the engine seemed to do it again and again during the day . i checked for weeds etc and could see no problem the fuel bulb was hard when i checked it while stopped. on the long run in the engine seemed to be running alot better and it ran fine all the way in with no surging. it sounded like i was dropping a cylinder so now im wondering where to start searching for the problem and was hoping someone might have had this problem before.

i was to sunburnt to pull the plugs :facepalm: when i got back so this week im thinking of replacing the plugs (maybe oiled up) draining the carbs (florida so could have water in it) and possible thinking about changing the float needles (maybe one is sticking) any surgestions would be welcome.

 

[boobie]

Re: 1986 evinrude 120 surging

You could have carb or ignition probs. Change the plugs, try it and get back to us.

 

[glenn property of pam]

Re: 1986 evinrude 120 surging

changed the plugs. also did a compression check as i was there which turned out good. the plugs were very wet so im thinking shes a little rich at very slow speed. last run was a fast run followed by a real long no wake slog back to the ramp where i shut the boat down then winched it on the trailer so im figuring the plugs reflect the slow troll in. going to be a while before i get back out due to family events and work but the way it was acting could have just been a wet plug which is why it sorted its self out later in the day. will get back when i finnaly get a day to go fishing.

 

[glenn property of pam]

Re: 1986 evinrude 120 surging

think i might have found the problem. it seems that i may have knocked the red lever slightly while working on the trim box so it wasnt pointing all the way down :facepalm: would explain why it was running rich at low rpm. still to busy with work to get out and test it but i hope thats all it was

 

[Daviet]

Re: 1986 evinrude 120 surging

Let us know after you get a chance to test it.

 

[glenn property of pam]

Re: 1986 evinrude 120 surging

mate borrowed the boat. hes the designated driver most trips so hes proberly got more time driving it than me and was there when it was playing up. he said boat runs great again no more surging and it starts quicker as a added bonus so im happy its fixed. going to make sure i get a spare set of plugs to keep on the boat as its hard to find a auto store that stocks them and the marina charges top dollar for theres.

 

[Daviet]

Re: 1986 evinrude 120 surging

Glad you found your problem.