1990 3cyl 90 HP cutting off

[doug1257]

Friend has a 1990 90hp that starts and runs good for a few min. Then just shuts off. The motor had been sitting for ablutions a year. Compression test and spark test good. Rebuilt carbs and fuel pump. Replaced primer bubble with OEM bubble. Cleaned fuel tank and lines. Checked tank vent. Hitting choak has no effect. Also tachometer is doing crazy things. Motor is on a 24' pontoon boat. Any thoughts on what's causing problem.

 

[ondarvr]

Re: 1990 3cyl 90 HP cutting off

When it shuts off does it slowly die, or does it act like you turned off the key? If it begins to slow down and maybe surge a little before it dies look for a fuel issue, if it just instantly shuts off its typically electrical. Spark can be good when the motor is cold but as it warms up electrical parts may start to fail.

 

[doug1257]

Re: 1990 3cyl 90 HP cutting off

It's almost like you cut the key off. But when I ran it the other day after all the fuel related work it seemed to run longer than it had been. As I let it warm up at the dock I pushed the rpm's up to around 1800 for a minuet and the tach bounced around and fell to 200 then just bounced around a little. When I pulled away fromm the dock and ran it up it was showing 4800 rpm's.

 

[doug1257]

Re: 1990 3cyl 90 HP cutting off

Also it will start right back up after a few seconds and run a little bit then do the same thing again.

 

[smittylv1]

Re: 1990 3cyl 90 HP cutting off

Tach gets it's signal from the stator pulse at the rectifier. Check these components/wiring.

 

[doug1257]

Re: 1990 3cyl 90 HP cutting off

10-4 will check that. Thanks. Could that cause the cutting off also?