I have a 1979 85 horse evinrude that was running fine on Sat., but on Sun I was having problems when running wide open. It would slow down then speed back up like it was starving for fuel. I didn't have any issues when running slow, and when I had my buddy pump the ball while we were running it was fine. I checked my connections and all seem fine. I was wondering if there is a fuel filter somehwere. I pulled the cover and didn't see one, but I know nothing about outboards. Any help or suggestions would be greatly appreciated.

So, when your buddy squeezed the primer bulb it ran fine? Follow the fuel line under the hood after it enters the cowling and see if there's a inline fuel filter.

If that's not the problem it sounds like a weak fuel pump.

marine_man

Or check the spark plugs

I would check fuel tank venting. It could also be the primer ball. The primer ball also is a check valve, and they are notorious for failing. Make sure if you buy one that you get a good quality OEM (original equipment manufacturer) one, such as geniune OMC, Mercury, Yamaha, etc....

I had a similar problem pump the bulb and it would run at high speeds I had to replace the fuel pump . I would recommend replacing the hole pump and not just the just the kit I had a 79 that the plastic was swelling in the fuel pump after sitting at home it would work fine in the drive way then break down on the lake 3 kits later I bought a pump. RR

I would definitely check the fuel filter. On my '84 Evinrude, it's an opaque white canister with a size that would roughly hold a stack of quarters. Unscrew the top and check the filter screen for debris/gunk.

Primer bulb could be your problem (a good thing to replace anyway and cheap/easy to boot).

Make sure you don't have water in your gas. I did 2 years ago and it caused a lot of hesitation and up/down in RPM's. Disconnect the line right after your primer and squirt some in a glass to see if it separates.

As mentioned it could be a fuel pump, but you'd probably have to bring in to replace that.

I just fixed this very same problem on my 87 Johnson 70 HP. Almost the same motor.

At first I thought the fuel (VRO) pump was bad. Turns out it was the primer bulb. A couple of bucks later and it's fixed.

Also, fuel lines can and do collapse, especially poor grade ones. Sometimes the collapse is internal and not seen from outer coating. Not to complicate the process, but another thing to consider.

Thanks for all the help guys. I have purchased a new preimer bulb and spark plugs, and will do some more checking this weekend. Hope to try it out on Monday or Tues. Will let you know when/if I figure it out.

please let us know how it goes! 99% of the time, the problem is something simple.

Replaced the spark plugs and primer bulb and have had the boat out twice since. Everything seems to be running fine. Thanks for all the help and suggestions.Hope everyone has a great memorial weekend!