Could I have found my problem?

[eavega]

Hi All

I have a 76 70 HP Johnson (70EL76D) that was giving me problems running full throttle after running for a while and being shut off. Note that this started happening after I performed a decarb on the motor. Compression was good, Spark was good, figured it was fuel. Although previous owner had told me carbs were rebuilt last year, I figured if I was going to take them apart to check them I might as well do a fresh rebuild on them myself.

In troubleshooting my problem and getting the carbs off of the motor and cleaned, I found a few issues, and I was wondering if anyone can tell me if any of the following would potentially cause the problem I was seeing:

1. one of the 4 bowl screws were missing off the bottom carb (I found it later in the lower motor cover)
2. The fuel lines feeding top and bottom carb had their outside covering split. The inside seemed to be intact.
3. When I removed the needle valves, they each had a ring of black on the tip which would clean off. It didn't seem sticky but took a little bit to wipe it off.
4. Lower cylinder spark plug boot had a spark leak if you were positioned just right. Found this one out the hard way!

So I rebuilt the carbs with all new kits (even replaced the core plug, which I had never done before), replaced the split fuel lines, replaced the one old fuel line in the motor (from the external connector to the fuel pump), cleaned the fuel pump screen, and replaced the spark plug boot. I'm hoping I've now conquered this particular beast.

I was just curious what problems (if any) the 4 items I found would've caused with running the engine. Any opinions are welcome.

Rgds

 

[fireman57]

Re: Could I have found my problem?

I would guess number 4 but any one or combination could have been the culprit. When you've tested it let us know how it runs.

 

[clemsonfor]

Re: Could I have found my problem?

We dont really know what "giving me problems" is. It sounds like if you ran full throtle then shut it off once restarted it would not run right?

Yea those cracked hoses may have been fine they may have been sucking air. And most likely ethonol was eating the rubber sending it all through the passages in your carbs. Your cleaning and running fresh gas and seafoam in it at WOT for 10 mins or so will do a good bit of cleaning. The cracked boot will give you a weak spark that can misfire esp in a vibrating motor hood at low rpms.

 

[eavega]

Re: Could I have found my problem?

Duh. I must've edited that out before posting. What is happening is that the motor is running great when first started up through its full throttle range. If I shut it down for a bit (reached the fishing spot, getting tube and rider all ready to go, etc) it will start and idle all day long, but it won't throttle up smoothly. If you baby the throttle (like a full 4-5 minutes to ease it from idle to WOT) it will then run, until the next time you shut it down then you are back in the "idle find but won't throttle up" mode.

-Rgds

 

[Daviet]

Re: Could I have found my problem?

Have you tried since you made the repairs, is it still acting up?

 

[fireman57]

Re: Could I have found my problem?

Make sure the carbs are clean and do a link n sync. Also, please make sure that you state the problem next time rather than here is what I did to fix it. Sounds like you had it conquered.

 

[eavega]

Re: Could I have found my problem?

Have you tried since you made the repairs, is it still acting up?

Nope. Weather was crap here today. I'm hoping to get it on the lake tomorrow, but with father's day plus 4 neighborhood birthday celebrations we are expected to attend, I'll probably have to wait until later in the week.

 

[eavega]

Re: Could I have found my problem?

Have you tried since you made the repairs, is it still acting up?

Finally got out on the water, and no change. Still idles all day long, but will stumble when you roll on throttle. I did verify I am not losing spark at idle or WOT. I am leaning towards a lean fuel condition. I had previously rebuilt the fuel pump, but have now opted to just replace it with a new one.
There is also a TSB for this very same problem on the '76 70 and 75 hp motors. Has to do with restricted passages in the carbs. I have verified that my motor has not been previously modified per the TSB recommendations, so I am going to attempt the mods myself. Problem I have is how did this motor make it for 35 years and now is when this problem manifested itself?

I 'll report results when the mods are complete and tested.

Rgds

 

[eavega]

Re: Could I have found my problem?

I finally got out on the water yesterday and tested. The modifications to the carb seemed to do the trick. I am still having problems rolling on throttle, but only when towing a tube. It seems that the additional drag will cause the motor to stall out. I'll next try to fool with trim and motor position to see if I can resolve.