76 70Hp evinrude problem

[unluckyboater]

i have a 1976 70 horse evinrude
the engine idles real good but when i put the boat on the lake after about 5 mins of riding then it hunches like a bad carb or drug build up but i have replaced the coils, wires,plugs,and rebuilt the carbs thinking that would help but it still does it.It It is actually worse now i'm lucky to get about 15 MPH's. what can be the problem?

 

[reload]

Re: 76 70Hp evinrude problem

I would like to try to help you but I am not familar with the term "hunches like a bad carb or drug build up".

 

[shipwreck]

Re: 76 70Hp evinrude problem

Did replace the float and needle when rebuild carb? did clean out carb?

Is it when you throttle up to certain point has problem or is all the time and top speed is 15 mph?

How long have had motor and did replace plugs ?

Did check the piston for carbon build and head bowls?

Check your cross flows if have them in cylinder heads for carbon build up when check your piston.

HIGH speed needles on carb do have them? see pic two i have two high speed needles behind bolts on my carb.

 

[chbailey]

Re: 76 70Hp evinrude problem

Rebuilding carbs would be a really good start.

 

[tashasdaddy]

Re: 76 70Hp evinrude problem

time to start with the basics, compression check all cylinders, spark check all cylinders jump 1/2 inch bright blue spark. post the compression numbers. there is no point in throwing parts at the engine, until you know you, have a good base to work with.

 

[jtexas]

Re: 76 70Hp evinrude problem

and describe your symptoms, please.

LOL @ "hunches like a bad carb or drug build up".

 

[Carbkid]

Re: 76 70Hp evinrude problem

Did you check the cooling system? Make sure your getting a good stream from the tell tale. If you haven't replaced the impeller recently it wouldn't hurt to do so.

 

[unluckyboater]

Re: 76 70Hp evinrude problem

"hunches like a bad carb or drug build up"
just like a car would when it has bad gas or something idles up and down

 

[shipwreck]

Re: 76 70Hp evinrude problem

listen to tashasdaddy statement he knows what talk about .

 

[chbailey]

Re: 76 70Hp evinrude problem

Yup, I second that. I tend to forget that a lot and go right for what "I think" is the problem.

 

[Tailspin]

Re: 76 70Hp evinrude problem

Neighbour had a similiar problem... new plugs installed boat ran fine for 5 min then acted like you discribe. New plugs again... idles fine.. then 5 min running problem was back. What was happening was aluminum was attaching it self to the plugs...and fouling them in 5 min... motor was on its way out as the cylinder walls were being shaved by a bad set of rings.

 

[jtexas]

Re: 76 70Hp evinrude problem

Neighbour had a similiar problem... new plugs installed boat ran fine for 5 min then acted like you discribe. New plugs again... idles fine.. then 5 min running problem was back. What was happening was aluminum was attaching it self to the plugs...and fouling them in 5 min... motor was on its way out as the cylinder walls were being shaved by a bad set of rings.

yup, that must be it, why bother troubleshooting, just jump straight into the complete rebuild

 

[iwombat]

Re: 76 70Hp evinrude problem

LOL @ jtexas.

Spark check and compression test for sure. But, it does sound suspiciously like an air leak. Have you tried using a different tank and hose?

 

[Tailspin]

Re: 76 70Hp evinrude problem

rebuild? was no mention of that at all.... wouln't new plugs be more like trouble shooting jtexas? this was discovered after all of the above was tested.. new gas lines compression etc. ...interesting how some ppl on here are in a pre-convetional state of moral development.

 

[jtexas]

Re: 76 70Hp evinrude problem

rebuild? was no mention of that at all.... wouln't new plugs be more like trouble shooting jtexas? this was discovered after all of the above was tested.. new gas lines compression etc. ...interesting how some ppl on here are in a pre-convetional state of moral development.

"pre-conventional" LOL.....nah I just sometimes like to throw out smartalecky comments without the or , jus to keep ya on your toes.........sorry bout that.........if you see any silver- or grey-colored foreign material on your spark plugs, it's a sure sign of real trouble.............