1976 Evenrude 70hp Problems

[craving94509]

Out on a friends 17 ft fiberglass runabout. He bought a used Evenrude 70 hp motor to replace his 50 sizzler. We took the boat out and it would not get above 2600 rpms and just would not get up on plane. He called the prop shop and told him the issue and that he had a 13-1/4x17 prop. He said to check the cavitation plate and make sure it was 1/2 inch below the bottom of the boat. He adjusted the motor accordingly, and it made zero difference.

Today we took it back out and I noticed the butterfly's do not move at all from idle to wot. Also adjusting the fuel mixture screws did nothing.

The boat idles fine and the bulb stays hard after its bbeen pumped. We cleaned the fuel filter on the motor and replaced the inline filter before the bulb.

He and I are both lost and hope so
meone can help shed some light.

Mike

 

[daviet]

You need to start with some tests, check the compression and spark. The compression should be at least 125 and be within 10% of each other. The spark should jump a 7/16" air gap and be bright blue.
If you have good compression and spark, move on to the fuel delivery system.

 

[Boobie]

If the butterfly's don't move in the carbs it's sounds like some loose or slipped linkage. Get a manual and do a sync and link on it.