Evinrude 70 Outboard motor "hunting" when at full power - any ideas ?

Question

Hi there,

i've recently purchased a boat with an Evinrude 70 outboard motor on it. It fires up nicely, but once it's been at full throttle for about 10 seconds, it starts jerking or hunting - stays at full power, then back off, then back to power - as if someone was opening and closing the throttle over and over. I've replaced the fuel line, but that didn't help

Any ideas ?

Answer 1

I gotta agree with tall chicky here

Last summer my Mariner was doing this and it was fuel supply.

In my case the little pin in the end of the fuel line fitting was bent and was getting enough fuel to start and run slow speed but would starve out at higher speed.

Might be the fuel pump, those are items that are relatively easy to check and replace.

Answer 2

It sounds to me like could be a rev limiter problem,  I would also have it checked out.

Answer 3

Definitely starved for fuel or air getting into the system  Does it have a fuel filter between it and the tank? If so, check that.  Mine did it because the filter was clogged.  And it wasn't old either.  Also be sure it's not over heating. If used, the impeller in the water pump could need replacing.

I had to put a kit in my water pump last year also because of shallow water areas and sand.  24ft tritoon w/115hp Yamaha.

Answer 4

well if you think it is fuel related push in on the primer and see if that helps if it does you probably have a carb problem. but when you say "jerking" it almost sounds like you are describeing an ignition miss. does it happen so fast its like somebody throwing a switch? if it is its probably ign related. what year is it, how much time is on it add this to your question and I will try to help. do you have a built in fuel tank? if so place on a six gallon tank to rule out boat fuel problems. if you are running on a small tank is the vent open. also check the hose connectors they wear and leak air. you can also have someone "squeeze" the primer bulb on the fuel line to check for fuel delivery problems contact me thru answers be glad to help. ps those engines were NOT prone to gasket malfunctios. they did have them but not at a rate diff than any other motor. I had a whole fleet of them for two decades, and I have seen every coceivable condition on that motor, some of which omc never had!! that is one tough engine I have hundreds of thousand hours to prove it!    if you contact me give model # please