1974 85 hp Evinrude Issues...Help??

[bluediverdave]

I recently bought a 1973 Glastron V-156. I've put a lot of work into getting the boat back up to running well and looking good. I'm close but have a few issues. Number one, and most importantly, I'm having some trouble with the high end of the throttle. The engine (85 hp 1974) idles great and on occasion runs fantasticly at top speed. However, every time I've taken it out (only 4 now) it has lost speed at the top end. Today was the worst. It usually losses some speed (at least 10 mph) and then after running for a while it gets it back. Today, it never came back. The boat goes fast enough to plane out fine and cruse along, but not as fast as she will go. I noticed today that when I choked it it seemed to increase speed. I also wonder if my fuel/oil ratio is correct. I've been mixing 25/1 and I heard from a friend today that he believes that motor should be 50/1. Could this be the cause of the problem I'm having? I could really use some help figuring this all out and hopefully someone out there can assist. Thanks much.<br /><br />Also, need to replace the tilt pump...anyone know where I can get one that fits into that shorter reservoir? Perhaps one laying around your yard or something?

 

[ob15]

Re: 1974 85 hp Evinrude Issues...Help??

I'm sure the experts will add input but it sounds like you have a fuel problem. Things that might help<br /><br />clean carbs<br />replace old dried up fuel lines<br />check tank for obstructions (including vent)<br />could be fuel pump too.<br /><br />Post you model number & others can help with the pump. Oil mix is probably 50:1 and someone will confirm that.

 

[LubeDude]

Re: 1974 85 hp Evinrude Issues...Help??

I had one of those vintage engines on a Ranger Bass Boat, The oil ratio is indeed 50:1. Is the speed all of a sudden just dropping 10 MPH, or is it gradual? If it is all of a sudden, like you dropped a cylinder, its probably one of your coils. I had that happen to me and I had to take a marine tech out with me with the cover off so he could tell me which coil it was. If it is slowly happening, it may be over heating.

 

[gibletts]

Re: 1974 85 hp Evinrude Issues...Help??

You might be fouling the plugs with that 25:1 mix?<br /><br />dm

 

[Walker]

Re: 1974 85 hp Evinrude Issues...Help??

I think you are loosing a coil after she warms up. Pull all the poils and clean the ground straps and where they bolt to the block and see if that helps.