'79 Evinrude 35hp: backfires since rebuild

Joined
Mar 1, 2005
Messages
958
During fishing opener this spring, my 1979 Evinrude 35hp overheated and blew the gasket. The shop fixed it for me and said that there was no apparent cylinder damage. I got it back and struggled to get it running. It finally started and kept running. After putting along for 1/4 mile I hit the gas to get on plane. Almost immediately I thought I hit a log or rock. This happen three more times as I realized that the motor was somehow backfiring. This never happened again during that trip in May or since.

However, last week as the weather cooled again into the 40s and 50s, it started "backfiring" again. I quickly realized that if I putted along for a longer time when the engine was cold/first-used, it wouldn't backfire. It always worked fine after running for a while.

The "backfire" doesn't really have a sound like a car would make when it backfires. Each time it happens it feels like I just hit a log, meaning that the motor kicks causing the entire boat to shake. The sound is rather muted.

I'm fine with just letting the motor warm up longer before getting up on plane, but want to make sure that I'm not damaging the motor with each use. What is this backfire? Can I assume that it's related to the spring repairs?


I run my Evinrude on a 16.5' Fisher from 1985 with the OMC-specified prop and nothing else special. My loads vary from just me, to adding the wife, to four people and gear.
 

iwombat

Captain
Joined
Jul 12, 2006
Messages
3,767
Re: '79 Evinrude 35hp: backfires since rebuild

That's a classic description of a worn clutch dog and forward gear.
 

Xcusme

Commander
Joined
Apr 21, 2003
Messages
2,888
Re: '79 Evinrude 35hp: backfires since rebuild

Hmmm, I think there's a bit more devil in the details....you said "I got it back and struggled to get it running. It finally started and kept running."

It very well may be the clutch dog as Iwombat mentions, but I'd pull the flywheel and check the crank shaft key too. Check to be sure it's not partially sheared.
 
Joined
Mar 1, 2005
Messages
958
Re: '79 Evinrude 35hp: backfires since rebuild

I only struggled to get it going on the maiden voyage after being fixed. It starts on the first pull like always now.

I'll pull out my manual and read about the clutch dog and forward gear. Thanks guys.
 

Don Hansen

Petty Officer 1st Class
Joined
Sep 17, 2007
Messages
230
Re: '79 Evinrude 35hp: backfires since rebuild

Pardon me for jumping in here. I'm not an expert on outboards but I do own an evinrude 35 hp. You say it over heated so I assume the water pump was replaced. If I remember right the shift linkage has to be disconnected by removing a plate in the side of the section between the powerhead and the lower unit. Maybe when they put it back together they didn't adjust the linkage properly.

Don Hansen
 

Walker

Captain
Joined
Jun 15, 2002
Messages
3,085
Re: '79 Evinrude 35hp: backfires since rebuild

Sounds to me like "lean sneeze" Try turning the carb adjustment knob counterclockwise until it stops sneezing.
 
Top