70hp Evinrude ignition problem

[brockly_9000]

I have been now battling this problem for 2 months. At first it will run fine, for bout 15 min. Its a small lake so I'm on and of the throttle. After bout that amount of time, Ill back off the throttle down to almost an idle to turn around. I give it gas again and it bogs. It will run WOT but barley makes plane. The longer i keep it WOT it slowly picks back up. So Ive done tons of tests from the repair manual. And everything checks out. Ive replaced the power pack last fall, cause it did lose a cylinder. Now I have spark all across the board even when its dogging. Ive been through the carb. Rebuilt completely 2 years ago, and i cleaned them a couple weeks ago. Also fresh gas, all new gas lines from the tank to all the carbs (no leaks). Rebuilt the fuel pump last week. Tested the timer base yesterday via how the book said. All came out fine. This is my first boat, and cant afford to take it anywhere at shop prices now days. Any help would be greatly appreciated.

 

[jtexas]

Re: 70hp Evinrude ignition problem

What year motor?

water/debris in the fuel tank?
fuel line holding pressure?
fuel tank vent open & clear?

Carb throttle valves all closed at idle, horizontal (not beyond) at WOT, parallel throughout their range of motion?

Choke plates staying open (except when choke is engaged)?

Do the spark plugs tell you anything? (google "reading spark plugs")
What spark plug are you using?

Last water pump service?

What's your compression?

Sometimes just cleaning the carbs is enough, but when its not, you have to do it again with the kits. That's my suggestion (assuming compression is good).

 

[brockly_9000]

Re: 70hp Evinrude ignition problem

1980Well its a new tank so thats good. Replaced the line from the tank all the way to the pump. With a new primer bulb and its holding. Choke solenoid is broke so i manually choke it and is staying open. Plugs are clean everytime i pull them running champion l44cj4. Water pump not sure bout, but its not overheating and is pumping great. Compression is 120 124 and 130. The weird thing my buddy just bought a boat with a 65 johnson a bit older then mine, it has the same problem

 

[gunny5]

Re: 70hp Evinrude ignition problem

Hey

I have the same issue on my 1987 70hp Evinrude. Tried loads of things but still in the dark. Could it be the temp switch? Engine in S.L.O.W. mode?

Keep me posted!!!

 

[jtexas]

Re: 70hp Evinrude ignition problem

No slow mode on 1980 model.
The difference in compression is borderline, but probably not causing this problem. I'd do a decarb (there's a good write-up on that procedure in the engine FAQ section of iboats), see if the top cyl comes up any.

This is a classic symptom of clogged carbs, once you've ruled out compression & spark & bad fuel, a carb rebuild will fix ya up.

There's a carb rebuild thread in the engine FAQ section, it shows how to fabricate a jet removal tool (don't use a regular screwdriver on the jets, too easy to mar that soft brass, which changes the fuel/air mixture).

After the rebuild, follow the link & sync procedure in the manual, any questions just ask.

 

[gunny5]

Re: 70hp Evinrude ignition problem

I just solwed my problem, simillar to yours.
And as jtexas say's, my issue was a clouged carb. More specific a clouged high speed ori in top carb...

 

[brockly_9000]

Re: 70hp Evinrude ignition problem

Well Ill give that a shot. Im running out of idea's. Dont have much to lose. Thanx

 

[thewiles]

Re: 70hp Evinrude ignition problem

it doesn't take much to get those jets clogged. Even if you have recently cleaned them, try again. I have gotten bad gas from the pump! Fresh gas isn't always as fresh as you think.