1978 evinrude problems

[looneeetunes]

hey guys new to the group, just trying to learn, listen and solve some of my probs.
i have a 1978 evinrude 85 hp. this thing is eating spark plugs for lunch (fouling them out) and drinking gas pretty heavy. took about a 20 min cruise today and drank about 3 gal. it is pushing a 28 ft pontoon, but when it was running right it dint use that much gas.
i put in a new set of plugs and first trip out it ran good for about 10 min. we shut it off and swam ect for about 2 hrs. cranked it up and it had that miss again. not a real dead miss just kind of shakes the motor and boat. it has backfired thru exhaust a couple of times on start up lately. is it carb probs? and what can i do? thanks.
a little background i am one of those shade tree mechanics. worked on cars all my life and past 10 yrs some on boats. i know my way around a wrench, and can follow instructions. got any ideas? its dark i can get numbers on motor tomorrow if needed.

 

[Bob_VT]

Re: 1978 evinrude problems

Welcome to iboats!

Rule of thumb an outboard drinks about 10% per hour at wot so an 85 would consume about 8.5 gal per hr at wot.

A 28' pontoon is a good size boat for the 85. Is this a new to you boat and motor? Do you know what prop you are running? If you are running the wrong prop for the job it could load up the plugs. Are you running 50:1 gas/oil ratio? The 85 does best with champion plugs.

Yes it could be carb problemd but they are easy to rebuild just a PITA to get to the nuts properly (a bunch of swearing does not help! ).

Have you decarbed the motor yet or recently? Many people have neglected this and it does help.

Try out search function and sit back.... do a bunch of reading. Order a good manual and you will feel better.

 

[looneeetunes]

Re: 1978 evinrude problems

yes this is a fairly new boat to me. i have had it for a year. so far i have had to replace a coil and a power pack.i havent decarbed it. i have been reading about that on this forum tho.. and have decided to do it. i also found a post about roller marks on carb. i noticed this i think the other day. i noticed it a little odd roller didnt exactly match up. was close but no cigar. but i didnt know if it was supposed to be that way. i will double check that tomorrow. i have been replacing plugs with autolite. could those autolites be prob? they cross referenced them with champions, because they didnt have them. the autolites are plugs with hooks. the first set it took out were hookless plugs. does that make a difference?
thanks in advance for the help

 

[looneeetunes]

Re: 1978 evinrude problems

sorry i only answered half of your questions.. i am running 50:1, and i dont know what the prop is. it is a stainless number. what pitch should it be at?

 

[krogie]

Re: 1978 evinrude problems

i have 76 model 85 and the champion plugs do alot better. as for the fuel consumption mine does about the same , these 85's are close to the 115's in the amount of fuel they consume. and a carb rebuild is fairly easy considering you know tour way around the tool box.

 

[looneeetunes]

Re: 1978 evinrude problems

update.. i put in some champions, got my roller marks worked out, found electric choke was sticking half closed sometimes (cleaned and oiled all that up, think thats fixed) i noticed when i had the breather cover off when i choke it top carb pours some gas out front of carb.. time for rebuild??? or is there an adjustment???