1998 50 HP Evinrude run-ability issues

[cloupej]

I just acquired a 1998 pontoon with a 50HP evinrude motor. My first outboard! Overall it is dependable (Never left me floating). It typically starts good, may have to crank it a few times when cold but it starts and idles great. I live in a channel so it takes about 3-4 minutes to get to the lake. Usually, when I get to the lake I can easily get it up to 3000-3500 rpms with out a problem, It runs smooth without any problems, within about 30 seconds or so it starts shaking like its going to jump off the back. If I back it down to 2400-2500 rpm it smooths out and I can cruise all day at that rpm. If I try to get creep above 2500 rpm it starts to shake again. I have had the prop checked and it looks relatively new. It almost acts like a fuel problem. I am hoping it is that simple. If anyone has experienced anything like this please let me know on what to look for.

Thanks in advance for the help.

 

[hall832]

Re: 1998 50 HP Evinrude run-ability issues

IS 3000-3500 rpms your wot.

 

[boobie]

Re: 1998 50 HP Evinrude run-ability issues

Is the over heat horn working properly ?? Find the tan wire that goes to the temp sender on top of the cyl head, disconnect it, start it up and ground out the side that comes from the wiring harness. The horn should blow. It sounds like it's going into SLOW.

 

[cloupej]

Re: 1998 50 HP Evinrude run-ability issues

Is the over heat horn working properly ?? Find the tan wire that goes to the temp sender on top of the cyl head, disconnect it, start it up and ground out the side that comes from the wiring harness. The horn should blow. It sounds like it's going into SLOW.

No, it is not WOT, I have just learned to slowly increase the RPM's, 8 out of 10 times it will start shaking at 2500 rpm's,
the other 2 out of 10 times I can gradually get it up to 3000-3500 rpm range for maybe 20 seconds before it starts to shake. The only way I can stop the shaking once it starts is to reduce the rpm's under 2500, then it runs fine, as long as I stay under 2500. But, with all that being said I have never been greater then the 3500 rpm, I do believe that I do have more throttle left.

I do get an alarm when I initially turn the key on and the alarm lights flash as well. I don't know if that constitutes the overheat horn working properly. I can check that next time I am at the lake.

 

[hall832]

Re: 1998 50 HP Evinrude run-ability issues

Sounds a bit like your dropping a cylinder. Did you try pulling each plug wire while its running. one at a time and if you pull one off with out it sounding different that will be the cylinder that is not firing for what ever reason. Comp-Fuel-Fire.

 

[hall832]

Re: 1998 50 HP Evinrude run-ability issues

Supply more information on the motor model and serial.

 

[boobie]

Re: 1998 50 HP Evinrude run-ability issues

As a wild guess, you could have a bad power pack on it which kicks it into slow. Seen it happen.