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1976 Evinrude 70hp Not throttling up/bogging down when throttling

S

SteveA98

New member
Hello everyone

i have a 1976 evinrude 70hp.. my issue is that while in the water it won’t throttle up, it will troll around, but once I go to speed up it won’t go anywhere then stalls.. starts right up and idles.. I have cleaned the carbs, replaced all the fuel lines, new fuel pump, new impeller, replaced portable gas tank cap with a vented one, new spark plug, new coil and wires.. I have no idea what is going on, is it the timing, could it be running too lean some how, running to rich? I have no idea at this point, very frustrating.
 
Do the standard steps.-----Compression test first.----Post your numbers.-----Test for spark.----It should jump a gap of 3/8" on all 3 leads.-----And how did it run for you last season ?----Sounds like it might be running on 2 of 3 cylinders.
 
Thanks for the reply racerone

so I’ve have the boat and motor for about 3 months I bought it from a guy not far from me and he said it was running good then started bogging and couldn’t figure it out. I did a compression test on it when I got it 110 psi in all 3 cylinders.. I didn’t check for spark because the coils looked new they were the Amazon sierra ones.. but found out 3rd cylinder wasn’t firing, the coil wasn’t working, replaced that took it out and was running great for 10 min got to plane then once I throttled back and went to speed up it started bogging again.. i went back while my Dad drove the boat and wiggled the spark plug wires and it would start throttling up then stop. I ordered and put on OEM coils, haven’t taken it out yet, just want to make sure everything is good to go.. I did notice on the top spark plug a little bit of milky oil so I went ahead and ordered a head gasket and cover gasket.. last thing I looked up spark plug gap for it and it said .040 and they are measured correctly but now I’m seeing that it’s supposed to be .030 how much of a difference will that actually make?
 
Some will argue.----Remove cylinder head and inspect cylinder walls.-----Head gasket is cheap item in the big picture.
 
Ordered a head gasket yesterday should be here this week.. I got concerned because I saw milky oil on the top spark plug not a lot but enough to concern me
 
Carry on with the trouble shooting.--------Motor needs 4 things to run.----Correct amount of fuel.-----Spark at the right time.-----Crankcase compression.----And compression in the cylinder.-----Maybe water is leaking into cylinders from water cooled exhaust covers.
 
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Yes, it has a manual choke so while my dad was driving I would close the choke, nothing, and then proceeded to open it a little at a time and nothing changed
 
It will bog when hard acceleration and slow, but I took it out today and I adjusted the choke till it would no longer bog, when I found the sweet spot it would throttle up every time, that was with the hood off, once I put the hood on and kept the choke in the same spot it started bogging again
 
What do you think could be wrong with the carbs? I went through them looked spotless, but went through and cleaned everything anyways
 
You are happy with 110 PSI compression.-------Perhaps there is a service bulletin to do with carburetor modification for this year ?
 
So I replaced the head gasket and now I’m at 120 psi.. but I’ll try and find a SB on the carbs.. any idea where I’d be able to find one?
 
Thank you for the reply and the help Jim, do you think it’s worth it for me? I’m capable of doing it, but if it’s not worth it then I’ll skip out.. will running it slightly choked cause any major damage? And what kind of danger?
 
I had the same issue you did, until I did a PROPER link and sync. You need the factory manual.
The factory bulletin issue is easily confirmed by tapping the choke switch for 1/2 second as described in the bulletin.
It gets you over the hump at around 2000 rpms and takes right off. For me it was not worth messing with carbs for such a small issue.

Jim
 
I don’t have a manual but will look around for one.. as for the link n sync I can do it, but how hard are the instructions for it? I’m very hands on/ visual learner.. so if it’s pretty straight forwarder all good, if not may take me a little time
 
The link n sync was confusing because in the manual it jumps all over the place.
It isn't in one precise place in the manual.

Jim
 
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