1967 Evinrude Starflight-S 100 HP no power or loosing power on the water

[chuntag95]

When on the lake the motor will idle in neutral just fine and tack up to 5500 RPM every time you try it. In gear the tach stops at around 2000 when trying to go WOT. If you leave it there it will eventually start to increase the RPMs but only gets to 4500. I have run it at 5500 RPM and 32 MPH recently and now when it finally gets going it tops out at 4500 and 25 MPH. It will run for a while then cut out. If I stop and put it into neutral it will run right up. I think it is a transmission issue but not 100% confident on that diagnosis. Hoping someone here will have seen this issue and solved it.

 

[racerone]

I doubt that it is a transmission issue.--------In this case reving a motor up in neutral means nothing.---It will rev up running on 2 of 4 cylinders.-----Start with a compression test.---Then check for strong spark on all 4 leads.---If those are good look for fuel issues.----Water in the fuel ?---Does bulb go hard on start-up ?---All carburetor jets verified clean ?

 

[chuntag95]

I'll do a compression test again. I'll also verify spark. I have been buying my fuel at the normal station I fill up my truck and not using marina gas. The bulb stays hard. I rebuilt the carb at the end of last year but haven't pulled it down this year. It may have 10 hours on the new jets and I do have a pre filter before the one in the fuel pump that seems to be clean. If I don't find issues with the first I'll take it apart too. Thanks for the reply.

 

[F_R]

You already know what a pain that carburetor is. Float level is difficult to set without the special tool. However, you seem to be saying it ran ok after you worked on that. At this point, I'd simply pull the high speed jets and make sure they are clean. If they are, you probably don't need to dig any deeper into it.

You should not be revving that thing up in neutral. If it were to suddenly kick in and run on all 4 cylinders, it may go to 10,000 and blow to bits. Even 5K in neutral/no load is asking for disaster.

 

[chuntag95]

F_R thanks for the tip on the revving it up. I don't want to tempt fate on a 48 year old motor. The compression test gave me 105-110 for all 4 cylinders and it the same as it was when I ran it last year. All 4 cylinders had strong blue spark. Next step will be pulling the high speed jets which I'll do tomorrow.

Thanks again for the info and advice.