Mercruiser 3.0 cranks but wont start

[newboater89]

I have searched this thread for answers to a unique problem. It's a 1989 searay 160 with mercruiser 3.0L motor.
At first it would not crank at all when turning key. Starter was fine because jumped it with screwdriver but solenoid wouldn't jump. Replaced starter/slave solenoid and then the boat would crank using the key but would not start. Tried many times it would crank by turning key but wouldn't start. Then one time as I tried it made a loud buzzing noise or grinding (can't tell) as it was trying to start. Now when i turn key it doesn't even crank anymore. Gauge still work but when turn key it won't even crank. Tested starter (by jumping it with screwdriver) still cranks. Replaced solenoid again and when jumped it cranks but nothing from the key at all. It's so frustrating to take 1 step forward only to start from square one

 

[alldodge]

Welcome
What is the motor serial number?

Turn the key to start and hold it there while moving the throttle handle Fwd/Rev slightly. If it cranks when moving the handle then it's the neutral safety switch

If it still does not crank, then use a voltmeter and measure the key switch on the Yel/Red wire in start position.

 

[Scott Danforth]

being a 1989, the boat has some age. you may have bad connections between the battery to the motor to the helm. After the quick checks above, start at the battery, and clean every contact until it is shiny

additionally, you should still have points ignition. once you get the cranking situation addressed, you will need to service the points.

 

[1960 Starflite]

Mine is a 1979 and uses glass tube fuses. Same symptoms, I checked Ignition fuse in place with ohm meter, OK. Checked while engaging starter, no voltage on engine side of fuse. Released starter and voltage returned to engine side of Ignition fuse. Pulled fuse, oxidized badly, cleaned, replaced and engine started.

 

[newboater89]

being a 1989, the boat has some age. you may have bad connections between the battery to the motor to the helm. After the quick checks above, start at the battery, and clean every contact until it is shiny

additionally, you should still have points ignition. once you get the cranking situation addressed, you will need to service the points.

The key was Cranking the boat fine until it made that buzzing/grinding noise and then all of a sudden didn't crank from the key anymore. Still cranks when jumping starter and solenoid. Also I cleaned all contact points in first place that's how I was able to get it to crank from the key. I just want it to crank again from the key then I'll move to ignition troublshooting

 

[newboater89]

Mine is a 1979 and uses glass tube fuses. Same symptoms, I checked Ignition fuse in place with ohm meter, OK. Checked while engaging starter, no voltage on engine side of fuse. Released starter and voltage returned to engine side of Ignition fuse. Pulled fuse, oxidized badly, cleaned, replaced and engine started.

This issues happened within minutes, first it cranked properly from key to all of a sudden not cranking from the key at all after the buzzing noise. All fuses are fine I checked first that's how we were able to crank it from key in first place before it all went downhill

 

[newboater89]

Welcome
What is the motor serial number?

Turn the key to start and hold it there while moving the throttle handle Fwd/Rev slightly. If it cranks when moving the handle then it's the neutral safety switch

If it still does not crank, then use a voltmeter and measure the key switch on the Yel/Red wire in start position.

Not sure where serial is.
I will try this. But you think the neutral safety switch could have bad right away like that. This issue happened literally seconds apart. Was cranking fine from the key, next minute stopped cranking from the key. This all happened after the last time we tried cranking from the key it made a loud buzzing/grinding noise while trying to crank

 

[alldodge]

Don't know what was buzzing other then the oil pressure switch turning on the buzzer. If it's the alarm buzzer then that's not an issue because it should sound until motor starts.

The neutral safety switch is something that can make a good connection and also bad connection, just depends. With age most things do wear out

With the crank and no crank and the buzzer buzzing then not buzzing can all go to bad connections, as Scott mentioned

 

[newboater89]

Don't know what was buzzing other then the oil pressure switch turning on the buzzer. If it's the alarm buzzer then that's not an issue because it should sound until motor starts.

The neutral safety switch is something that can make a good connection and also bad connection, just depends. With age most things do wear out

With the crank and no crank and the buzzer buzzing then not buzzing can all go to bad connections, as Scott mentioned

Which connections should I look at? Do you think it could be the key switch. How many volts pass thru the key switch. Multimeter read 8.4 when I did the test you recommended

 

[alldodge]

Volts at the Battery should be close to 12.7V
Should see the real close to the same everywhere else. Only getting 8.4V then need to clean connections.

Disconnect Battery cables then clean them. Leave cables disconnected and clean other ends on block and starter post.

Pull the 10 pin engine connector apart and clean the pins.

Look for corrosion and clean connections where found

 

[newboater89]

Volts at the Battery should be close to 12.7V
Should see the real close to the same everywhere else. Only getting 8.4V then need to clean connections.

Disconnect Battery cables then clean them. Leave cables disconnected and clean other ends on block and starter post.

Pull the 10 pin engine connector apart and clean the pins.

Look for corrosion and clean connections where found

I'll do that and let you know what happens. Something tells me that corrosion can't be issue because it was cranking before normally then all of a sudden stopped cranking from the key. This happened within 1 minute and hasn't cranked from key since

 

[newboater89]

being a 1989, the boat has some age. you may have bad connections between the battery to the motor to the helm. After the quick checks above, start at the battery, and clean every contact until it is shiny

additionally, you should still have points ignition. once you get the cranking situation addressed, you will need to service the points.

What are points?

 

[Scott Danforth]

What are points?

Read the stickies on points, and start researching. You are going to need a points file, feeler gauges, dwell meter, and a timing light

 

[Scott06]

What are points?

two good video explaining how points work. Take note of the spark strength that’s how it should be