70 HP Evinrude 3 Cyl. 1979-1984??? Throttle issues

Hi,

I have what I think is a 1979-1984 70 HP Evinrude outboard (Info plates missing).

Purchased a Key West 1990 boat with this engine.

The motor cranks and runs and you can shift it into gear with the water muffs on it and it seems to run O.K.

The issue is when it is in the water and cranks up and you attempt to put it forward gear it stalls and quits. With a lot of tries and pressing the choke button I was finally able to get it up to high speed and the boat ran fine.

I took it to a local marina and they did some initial testing and finally recommended that the carbs be cleaned. They actually spent quite a bit of time on it trying to get it to run properly i.e. taking throttle without stalling, but with no success. The owner was on vacation and is due back tomorrow and he may have some other ideas on fixing my problem.

Hopefully, he will find the correct solution.

Any ideas here would also be appreciated. Thanks in advance for any suggestions.

John

 

Clean the carbs, then a full service and fresh tuneup. I run into this all the time and it's 95% of the time, lack of regular maintenance and varnished up carbs.

 

Carbs

Hi PAR,

Thanks for your input.

Initially, I cleaned the carbs but didn't set the float height or mess with the low speed needles.

The marina took the carbs back off and recleaned them and also installed new gaskets in the carbs. They also inspected the linkage and sync'd the carbs. Still not working properly.

Hope there is not something major wrong with the engine. That would be hard to believe as it runs fine at cruzing speed.

John

 

Damaged or bent reed valves could do that. Also, the low speed coil under the flywheel.

 

Reed Valves

Hi gonzo,

Are the reed valves easily accessable or is that a major engine job?

The owner of the marina asked me if I had messed with a timing advance stop located under the flywheel that has to do with the timing. I told him I never had the flywheel off but a previous owner may have messed with it.

John

 

Thes engines were bad for this. The Merc 70 was also so finicky.

Clean carbs is essential and the timing cam adjustment is also and may need tuning by ear to get that sweet spot. Of course carbs should be opening at the exact same time but if that doesnt work try one opening a tad bit early to feed power on slowly.

You might also try absalute exact fuel oil mix. Fuels and oils have changed a bit since those days. Certainly too much oil would cause this.

You need a good man of on this old engine and tuning it in a tank adjusting and tuning as she goes.

 

If you remove the carburetor, the reed valves are right behind and can be seen.

 

Help

Hi Frosty and gonzo and others,

Thanks for your valued input.

The marina has not called me yet. Guess the owner is taking a look to see if he can figure it out. I had to replace one of the bushings in the lever that advances the timing prior to taking it to the marina. I am sure they checked the timing advance, but like you say it may need to be tweaked.

Hopefully, he will call by day's end.

John