Mercruiser 3.7 weak spark! Help!

[usmarine2147]

I just bought a 18’ Sea Ray with a 3.7 Mercruiser, having an issue. It ran last year great. Pulled it out of storage and it seems to have weak spark.

The battery is fully charged and it cranks over fine. I pulled the plugs and installed new ones, I replaced the coil and have new plug wires in the mail.

What are some things to check for? With the old coil I unplugged the wire off the distributor and put a spark plug in it. While cranking it had zero spark holding the plug against the block. After I replaced the coil it had spark doing same test but after testing it off one of plug wires the spark seemed week.

Still won’t start even with starting fluid!! HELP!

 

[Bondo]

Ayuh,..... Welcome Aboard,....... Change the Points,.....

 

[Scott Danforth]

or at a minimum service the points....which is file them, gap them, and with a dwell meter, verify.....then set timing...

 

[usmarine2147]

I will order new points and condenser and distributor cap as a kit online today and keep you all updated thanks for the help!

 

[Scott Danforth]

I will order new points and condenser and distributor cap as a kit online today and keep you all updated thanks for the help!

I would start with filing them. you have to file the new ones anyway. when points sit (no mater if new in box, or sitting in the dizzy over the winter), the contacts corrode

use a point file or your wife's nail file, pull it thru the contacts twice, set gap, verify dwell, then adjust timing

 

[kenny nunez]

Also test the + side of the coil when cranking the engine over, you want full battery voltage to the coil in cranking mode. If the voltage is very low or “0” then the start solenoid needs to be replaced. The internal “by-pass” contact in the solenoid is the problem. Be sure to get a marine grounded base solenoid if it needs replacement.

 

[usmarine2147]

I did test the + side of coil and it was showing great voltage while cranking. I will clean off the points tonight after work and set gap and see if I can get it to fire

 

[usmarine2147]

Thanks all for the troubleshooting I’m hoping I can get it running good for the weekend!

 

[usmarine2147]

UPDATE: I replaced the plugs, wires and coil. I cleaned the points under distributor cap. Got it to fire on the trailer, I backed it down the ramp and lowered the trim to let it run in the trailer and the second crank the starter went out..... now it just makes a whining noise and the gear does not seem to engage the flywheel..... I turned the motor over by hand, same result, I jumped the starter solinoid and same result!