1967 Evinrude 6hp Fisherman losing power

[mciulla]

How is everyone this balmy hot evening? I have a 1967 Evinrude Fisherman 6hp short shaft motor that runs great, starts first pull every time. The problem that I am having is that the motor seems to take of somewhat fine in forward when you first start out, but then as you go it seems to slow down and the rpms lower noticeably. Any ideas what might cause this? Any info would be greatly appreciated.

Also I am using an older metal fuel tank that is in great shape, but I do not see a vent screw on it anywhere including the fuel cap could that cause an issue? I also have a brand new hose and bulb on the tank along with new gas mixed 50:1. The motor runs very strong when in a tank.

 

[Daviet]

Re: 1967 Evinrude 6hp Fisherman losing power

Does it help if you pump the primer bulb when the problem occours.

 

[scipper77]

Re: 1967 Evinrude 6hp Fisherman losing power

My '61 fisherman was doing the same thing today. I tried pumping the ball but it had no effect. I plan on checking the spark plugs, changing the fuel filter, and of need be I will rebuild the carb this winter and replace coils.

I know its not much help to you but that's my plan for the exact same problem. (maybe a decarb is another possibility)

 

[mciulla]

Re: 1967 Evinrude 6hp Fisherman losing power

I also tried pumping the bulb with no success, I just tried replacing the spark plug but I can't water test it till the weekend!

 

[scipper77]

Re: 1967 Evinrude 6hp Fisherman losing power

Well I'm dying to see what it is cause I'm telling you I have the exact same scenario.

 

[mciulla]

Re: 1967 Evinrude 6hp Fisherman losing power

I hear ya scipper77 it is driving me nuts!!!!! Like I said the motor runs real strong and then loses it as you go along!!!!!!

 

[Daviet]

Re: 1967 Evinrude 6hp Fisherman losing power

Might want to check the high speed orifice to see if it is restricted or plugged.

 

[mciulla]

Re: 1967 Evinrude 6hp Fisherman losing power

Can you advise me on where the high speed jet is located on that carb?

 

[Daviet]

Re: 1967 Evinrude 6hp Fisherman losing power

Page #4 item #50.
http://www.marineengine.com/parts/v...ntage-evinrude-johnson/278871/27887100001.htm

 

[mciulla]

Re: 1967 Evinrude 6hp Fisherman losing power

Thank you very much Daviet, I will have to give her a try and see how it goes!!!!!

 

[Daviet]

Re: 1967 Evinrude 6hp Fisherman losing power

You're welcome, if that is not your problem come back and let us know.

 

[mciulla]

Re: 1967 Evinrude 6hp Fisherman losing power

Ok I took the motor out for a short run today. Before the test run I put in new plugs, and made sure that the high speed orifice was clean and clear. The motor as usual started up on the first pull and appeared to run rather steady with no loss of rpms which is a positive change, but it did not sound like it was running at full throttle. Could the fuel tank be causing a problem? I have an older metal fuel tank that is in great shape, but it does not appear to have a vent on it that I can find anyway. When you open the cap you clearly hear the tank release a lot of pressure. I do not know whether or not that can causes a decrease in rpm's.