85 hp Evinrude half power

[Rdjga]

I have a 1979 Evinrude 85 hp outboard that ran fine until recently. It starts ok idles a little rough. When I put it in gear it only runs at half power. After several minutes it seems to “catch” and run just fine at full power. It starts and runs just fine after that until the next time I put it in the water. I only use 100% gas and I have run a can of Seafoam through it. I also changed all 4 spark plugs. Any idea what the problem is?

 

[Lewis1111]

I would lean towards something on the electrical side. Maybe a bad power back or trigger...Would need to do some trouble shooting when the issues occurs.

 

[racerone]

Run with a timing light to see if it is ignition trouble.----If it is a plugged carburetor it needs to be corrected now.----No fuel going in means no oil going in to the bearings !

 

[Tassie 1]

I only use 100% gas

what does that mean?

 

[oldboat1]

50:1 mix (about 2 1/2 oz oil per gallon). Was Seafoam intended to cure the problem, or did the problem start after the treatment?

 

[Rdjga]

100% gas means no ethanol and yes I mix 50:1 oil to gas. The Seafoam was used to try to help cure the problem. I am also leaning toward an electrical problem I just am unfamiliar with boat engines and was curious if anyone else had experienced something like this.

 

[oldboat1]

Run with a timing light to see if it is ignition trouble.----If it is a plugged carburetor it needs to be corrected now.----No fuel going in means no oil going in to the bearings !

While in the lake, hook up the timing light (pick a plug wire), and have a helper start the engine and put it in gear. No flash means no spark. Repeat with each wire.

 

[Rdjga]

Thanks Oldboat that’s a great idea! I’ll let you know what I find.

 

[dabrackmaster]

Had same issue on my Evinrude 90hp v4. After reworking entire fuel delivery system, thought I had it licked.
Turned out leaving my engine in the UP position for transport after coming back home was my poison.
The gas eventually evaporates, leaves the 2 cycle oil behind.
Mine would take about 3 or 4 minutes before the engine would catch up with the throttle applied.

After that, ran great all day. Into the night, parked and fished for hours. Ran great back to the landing.

Then just like yours it'd do exactly the same next trip out.
FIX......i just let my motor down all the way while it's at home.