1977 Johnson 70HP Power Loss when accelerating

[Feltsoles]

I have a 1977 Johnson 70hp which looses power when throttling forward. It seems to idle O.K. although not quite as smooth as I would expect. I use the motor May 11 of this year and had this problem. I swithed gas tanks and everything seemed to work fine.<br /><br />I have now put new gas in the old tax plus another tank and both still have the above problem. Almsot seemes gas starved but not sure.<br /><br />I just installed a tach but don't believe that could cause a problem. If I take off the cover an trttle up manually, it seems o.k. although even then it will kill sometime.<br /><br />Any advice would be appreciated.

 

[leeray]

Re: 1977 Johnson 70HP Power Loss when accelerating

is this the first time you have run the boat it could very well be you high speed jets you might see what they are and check the book if they are not the right ones for your altitude that could be what your problem is i had the same problem with a 70 horse my self

 

[Feltsoles]

Re: 1977 Johnson 70HP Power Loss when accelerating

Thanks for the suggestion. Unfortunately, this engine has run very well last year and early this year.<br /><br />I keep thinking it is a fuel problem of sorts and I have checked the filter screens. They seem fine. I have read about having vented gas cans but mine have no vents. I know little about this.

 

[Feltsoles]

Re: 1977 Johnson 70HP Power Loss when accelerating

I forgot to add, if I use the acceleration lever manually (by taking off the hood) there seems to be plenty of accceleration.

 

[Feltsoles]

Re: 1977 Johnson 70HP Power Loss when accelerating

More info: I recently added a Teleflex Tachometer to my 77hp 70 Hp Johnson. I followed the instructions but they were a bit confusing. I contected the Tach ground to the ground on the control box, the purple wire in the control box to the send on the Tach, and I believe I connected the correct wire (I think brown) in the control box to the IGN. terminal on the tach. Is it possible I connected the wrong wire to the IGN which causes my motor to stop when under load???