1984 70hp Evinrude bogging down

[eric136]

I'm currently away on vacation (camping) and I'm having problems with my 70hp. Starts and idles fine but when I give it full throttle, it starts to bog and will not go on plane. When this happens, I push the choke in for a second or two and the boat takes off and runs without any problems. I don't have my shop manual with me, does anyone have any ideas that I could fix while I'm on vacation. I do have access to tools and air (if needed). Thanks, Eric

 

[Daviet]

Re: 1984 70hp Evinrude bogging down

Will it run properly if you pump the primer bulb? Having to choke the engine to make it run properly would indicate a fuel problem, air leak, fuel pump, carb problem. By squeezing the primer bulb you bypass the fuel pump.

 

[eric136]

Re: 1984 70hp Evinrude bogging down

I just replaced the fuel pump approx. 1 month ago when I was going down the lake and all of the sudden the motor appeared to be starving for fuel. At that time, I did pump the ball to see if it would fix the problem but it did not. I had the boat for approx 4 years and the boat sat for who knows how long so I decided to replace the fuel pump as proper maintenance. I do not have the problem now but have adopted a new issue. I could see if I needed to constantly choke the motor to keep it going at full throttle but once it gets on plane, it runs fine and I don't have to choke it.

 

[whitetailed]

Re: 1984 70hp Evinrude bogging down

I am having the exact same problems with my 1981 70hp. I have done eveything, Even if I pump the bulb no help. I just got this boat this season and it had run great. Now this. If you figure it out please let me know. I will do the same for you. I am going to take the carbs off mine and clean them up good, and replace filter.

 

[coffeeJunkie]

Re: 1984 70hp Evinrude bogging down

Wow ... exactly the same problem here too. I have a 1983 70hp Evinrude. On the first run of of the day, it seems to do fine for me. Once it has warmed up though - look out. I can usually get to pick up and take off if I give it throttle very, very slowly - and after it dies 4 or 5 times. I have tried pumping the gas bulb too.

I will let you know if I come up with anything. I will be working over the next few days.

 

[jtexas]

Re: 1984 70hp Evinrude bogging down

A cylinder is dropping out when you accelerate. It's a classic symptom of dirty carbs.

Eric, since your motor will run when choked that rules out every other possibility.

Daviet, first rule out a compression or spark problem (instructions are in the Engine FAQ section of iboats). Don't take it out to try running with the choke on -- whichever cylinder is starved for fuel is not getting any lubrication, so you don't want to run it like it is. Do the compression and spark tests instead.

Then rebuild the carbs with new kits.

coffeeJunkie yours sounds like it could just be a spark advance linkage, but its probably flooding, most likely due to worn carb float valves or sticky or misadjusted float height. cold engine doesn't mind the extra fuel. carb rebuild is the solution for that, too.

 

[coffeeJunkie]

Re: 1984 70hp Evinrude bogging down

jtexas - thanks a bunch for your insight. Is a carb rebuild something a novice mechanic like myself could do? I have rebuilt carb on a 350 chevy once. But I've never worked on an outboard though. Or would you reccomend taking to a professional marine mechanic?

 

[patrick4266]

Re: 1984 70hp Evinrude bogging down

do it yourself it's easier than the chevy carb. There are several videos on youtube explaining how.

 

[jtexas]

Re: 1984 70hp Evinrude bogging down

oh yeah, these carbs are remarkably simple devices. You are already basically overqualified for the job. ok, slight exageration.

Click on the "engine faq" section of iboats, there's a carb rebuild thread, including how to fabricate your jet removal tool.

carb kits, about $12 on iboats. you need 3.

you really should get a shop manual, I highly recommend the factory manual.

Seriously, nothing on this motor is beyond the scope of a determined do-it-yourselfer with some basic tools and a good manual.

 

[patrick4266]

Re: 1984 70hp Evinrude bogging down

I read the same thing over and over. "runs good on muffs, bogs down on the water" This is the same thing that happened to my 83-70hp-johnson. From my limited experiece heres what I had to do to get it right. First get the omc manual. Second check compression and good spark. Third, rebuild the carbs, easy, inexpensive and gives peace of mind. Replace all the gas lines, and have fresh gas make sure the bulb pumps up hard. I did all of that and it was still bogging down. Went back to the manual and asked questions in here. Had to time it and link&sync. Now it runs like a charm and I am very happy with it. I did not just read the manual and fix it right. I had to read it over and over and ask questions in here.