1968 Evinrude 18 h.p. Fastwin Wont Rev up to Max under load

[Matt 1968 evin 18 h.p.]

Hello everyone, this is my first post. I just bought a 1968 Evinrude 18 h.p. fastwin. I thought it ran good until I drove a friends of mine's boat which has the same motor, and it rev's up much higher. I replaced the spark plugs and both plugs are showing spark, and feel warm so I assume both cylinder should be firing. When I give WOT it seems to only give about 70% power, not quite revving as high as it should. I had a problem with the fuel connector coming off (from the gas tank), so I bought a new one and fixed that problem. But then the new one also started slipping off as well (I didn't clip it all the way) but when it did start to become disconnected the motor revved up and gave full power on a couple a different times. One friend of mine is saying its a fuel problem. My other friend says it could not be getting enough air and running way to rich, his advise was to clean the carb and go from there. Please any help would be great. I have very limited mechanical experience, but I think it's about time I start working on my own equipment to save money.

 

[nwcove]

Re: 1968 Evinrude 18 h.p. Fastwin Wont Rev up to Max under load

welcome to iboats!

first thing you should do is a compression test. then verify that its actually producing a strong 1/4 spark ....a 10$ open air spark tester will verify it. if those things check out, then its time to move on to the fuel pump and carb....which is an easy job, but it must be done properly!!
then i need to ask....where are you getting your fuel line connectors?

 

[kfa4303]

Re: 1968 Evinrude 18 h.p. Fastwin Wont Rev up to Max under load

Hi Matt. Welcome to iboats. Cool old motor you've got there. What spark plugs did you get? You want to use Champion J4C or J6C plugs with at least 50:1 mix. You should probably rebuild the carb if it hasn't been done in a while too. Here are some great links to familiarize yourself with your new toy. You can get any routine parts you need for the tune up right here at iboats. Holler if you get stuck.

Maintaining Johnson E & FD Serie
http://forums.iboats.com/engine-fre...kening-sleeping-outboard-boatbuoy-158086.html
1968 Evinrude 18802M 18 hp Outboard Motor Parts

 

[Matt 1968 evin 18 h.p.]

Re: 1968 Evinrude 18 h.p. Fastwin Wont Rev up to Max under load

welcome to iboats!

where are you getting your fuel line connectors?

I got it at a local bait shop. I was just the generic evinrude /Johnson fuel connector clip. I think it was my fault it slipped off, I needed to push it on and lock that metal clip better. As for compression test, that is not the problem, and the motor is getting spark, because as I mention earlier is did rev up to max on a few occasions (when the fuel line slipped off). I also forgot to mention that is seemed like it I was going through way too much fuel. So my 1st guess is that it is running way too rich and not getting enough air for the correct combustion mixture. Because when then fuel line slipped off, it must have been sucking in more air (that what I would assume made it rev up to the correct rpm). Thank for your help guys after this weekend I think I'm gonna try to tackle cleaning the carb.
As for the spark plugs, I got them from a guy who had the same motor I believe they were champion, and they are brand new and getting great spark. As for fuel lixture, yes I was using 50:1 I don't measure it perfectly if anything I add a touch too much oil so at the worst it would be like 48:1.

 

[F_R]

Re: 1968 Evinrude 18 h.p. Fastwin Wont Rev up to Max under load

The fact that it revs up when it runs out of fuel (leans out) does seem to indicate it is running too rich. Perhaps somebody installed the wrong high speed jet orifice plug. Or reamed out the original. OR the gasket at the center or the carburetor bowl may be shot, allowing fuel to bypass the HS jet. OR the fuel pump diaphragm may have a pin hole leak through it. That admits extra gas to the engine through the hole.