'84 evinrude 70hp dies at about half throttle?

Took my boat out for the first time today. Before taking it out, I had a local marine shop go thru the motor and be sure everything worked. Got it back a couple days later with a good report card. Well, got it in, cranked up, and it started and purred like a kitten. sat there letting it warm up a minute or so, then put it in gear and got out of the no wake zone. Started opening up slowly to see how it would do. Got to a little under half throttle and the motor started trying to die like i was running out of fuel. I've got a full fresh 6 gallon tank mixed. Fuel is mixed according to the instructions. It's the same fuel I put in before I put it in the shop so I doubt fuel quality is the problem. I thought maybe the vent cap on the fuel tank wasn't letting enough air in so I even pulled the cap off and it still did it. Sadly, I turned around and puttered back to dock and re-trailered the boat. I don't get it. I've had the boat out of the shop since Wednesday so It's only sat 4 days. Anyone have any ideas or suggestions? Anywhere before the point it messes up, it runs very smooth.

Re: '84 evinrude 70hp dies at about half throttle?

It could be a few things, id take it back to the shop and say they were wrong, get a refund or get them to do their job properly.
You could try cleaning the carbs out if you want to try it yourself.

Re: '84 evinrude 70hp dies at about half throttle?

First make sure all your spark plug wires are on. 3 bangers will idle beautifully on 2 cylinders. Done that :facepalm: . Next when you open it up try choking it & see if it tries to speed up. If it does - take it back to shop. If it doesn't - take it back to shop.

Tom B.
(LongLine)

Re: '84 evinrude 70hp dies at about half throttle?

Possible weak fuel pump. Next time you go boating, take a friend. When you get to mid-throttle, have the friend constantly prime the fuel hose bulb. This will force extra fuel into the carbs. If it runs just fine at WOT, as long as you constantly prime the fuel hose bulb, likely a fuel delivery issue, including a weak fuel pump. This problem may not have show up at the dealership unless they ran it hard in their test tank. They may not have done that if you did not indicate a high rpm running issue.

Re: '84 evinrude 70hp dies at about half throttle?

Think I may have found it. Waiting to get it in the tank or back in the lake, but it had an inline fuel filter which apparently was letting air into the line. I replaced the bulb, filter, and ends on the hose and the clamps. It seems to be holding fuel and filling fine. I'll update when I get to test it out.

Re: '84 evinrude 70hp dies at about half throttle?

the prime bulb should hold pressure for hours just sitting if it doesn't, there is a leak. follow the lines after primer bulb and you.ll find it

Re: '84 evinrude 70hp dies at about half throttle?

I had the same problem, different engine. Make sure you replace ALL fuel filters (I had three).

Re: '84 evinrude 70hp dies at about half throttle?

one filter should do just fine.