70 Hp Evinrude 3 Cly

[REAPERNINK666]

I Have a 70 HP 3 Cyl Evinrude that has a new power head on it. It runs fine out of the water and idles alright. When you put it in the water and crank it it will idle. When you go to throttle it or try to back it off the trailer it stalls. Any suggestion. New carbs, new plugs, new wires.

Bobby

 

[JB]

Re: 70 Hp Evinrude 3 Cly

It may be running on only one or two cylinders, reaper. Never believe a multicylinder 2 stroke with no load on it. Also, never believe a new part works until you see it work. That especially includes carbs.

With it at idle on the muffs disable each cylinder in turn by pulling or shorting plug wires (very carefully). A cylinder making power will cause the idle to drop or the engine to quit. A dead cylinder will make no difference in idle speed.

If you have a dead cylinder test for a hot, blue spark over about a 7/16" gap and test that carb by spraying some fuel premix into it while at idle.

Let us know what you find.

 

[HighTrim]

Re: 70 Hp Evinrude 3 Cly

Check to see if the timer base (starboard side, under the edge of the flywheel, linked to the throttle lever) moves smoothly without sticking when you advance the throttle.

Take the airbox cover off & observe whether the throttle plates are parallel.

Also, the timer base should start it's travel *before* the throttle plates start to open, else she'll fall flat when you try to accelerate.

 

[jay_merrill]

Re: 70 Hp Evinrude 3 Cly

It could also be a bad fuel pump. It may be working weakly and when it needs the higher fuel flow, the pump can not deliver.

 

[Chinewalker]

Re: 70 Hp Evinrude 3 Cly

You have a new powerhead. WHY do you have a new powerhead? Did the previous one blow? If so, WHY did it blow? Were the carbs rebuilt? Were they ruled out as a contributing factor? If the carbs were not rebuild during the rebuild, I would suspect them...
- Scott

 

[tashasdaddy]

Re: 70 Hp Evinrude 3 Cly

Link & sinc?

 

[REAPERNINK666]

Re: 70 Hp Evinrude 3 Cly

Hey Guy's

The Carbs Have Been Rebult The Fuel Pump Is Also New And Pumps Fuel Real Good Even At Full Throttle When Disconnested. Yes The Orignal Power Head Had A Bad Cyl In It And Could Not Be Fixed.

It Is Getting Fire On All Cyls Checked It With A Spark Tester Good Spark. Carbs Are Squarting Gas To The Cyls Also.

Has Me Puzzled.

Reaper N Ink 666

 

[ob]

Re: 70 Hp Evinrude 3 Cly

Without a model number indicating the year of engine it's difficult to troubleshoot potential carburetor related issues.Your symptoms could be something as easy as out of adjustment idle mix screws.However,some models have fixed orifices.They too could become restricted causing the same symptom.This and as mentioned above ,the link & synch of each carburetor is likely your problem.Insure that the carburetor/s link roller is exactly aligned on center with the scribe line on the fiber throttle cam,and 'just touching' when the controls are in the neutral position.This setting is critical to smoothe and responsive throttling under load.

 

[SiLiconD17]

Re: 70 Hp Evinrude 3 Cly

I'm with JB, do a plug test.

I had a twin cylinder Evinrude that was making spark, getting fuel, and had perfect compression. It turned out that one of the plug wires were bad to the point where when you opened the throttle, it wasn't giving that plug enough spark, even though you could see that it was getting spark. What I'm trying to say is that you can't take it for granted that you're getting correct spark by just looking at it.

What you want to do is get a good pair of insulated pliers (spark plug shockage hurts), and loosen the plug wires off the plugs a bit and crank the motor. One plug at a time, pull the plug wire with insulated pliers enough so that the arch doesn't get to the spark plug (so the plug doesn't fire). When you pull each plug, you should be able to tell a difference at idle after the loss of that cylinder. If you get to a cylinder that makes no difference to the idle when you pull the plug, that cylinder probably isn't firing right. It may be a bad plug wire, bad coil, timing off, any number of things if you figger that a cylinder is giving you problems. I have a piece of crap Yamaha 3 cylinder that's doing the same thing to me right now and I have a CDI unit on order (d*mn the Japanese and their complicated and expensive electronics).

Also, another dumb hint, but have you checked the reeds? Normally they don't go bad, but I've replaced them on an outboard of mine before.

 

[REAPERNINK666]

Re: 70 Hp Evinrude 3 Cly

The reed valves are brand new. Have checked them because I thought that might be the problem. They appear to be ok. This is the third one of these engines I have rebuilt and this is the only one giving me the problem. The carbs are fixed jets. I have toadley rebuilt them and the jets are new. I will do the wire test you suggest that is the only thing I have not done. I told you I put a new fuel pump on it. I replaced it with a high performace fuel pump which I have done on all of them.

This is a 70 hp 1987 model engine and the oil injection had been disconnected from it. It came from the navy that was used on a zodiac that was used to pick navy seals from the water in rescue missions. It run fine for about a year then started having compression problems. Thats when I found one of the cyl out of round. I bought a new power head and replaced it. Now all these problems.

Bobby