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1985 Sylavn

D

Duke32

New member
I have a 1985 Sylvan V171 with 200 murcruiser MGM 305 with thunderbolt ignition ( serial # S389755 ) would not go over 2000 RPM
I changed spark plugs rotor and cap and coil ,wires ohm good Now it runs fine
The disrtibutor cap has a port on side should it be capped or is there a hose attached to it and if so where does it go
also the ignition sensor is rusty can i clean it or should it be replaced
 
If your pick up sensor inside the distributor is rusty, REPLACE IT!!
The new sensor will be a three wire (two of which are bullet connectors) the third being a ring terminal to ground. You will need to change the current ring terminals used to connect the current sensor to the correct male/female bullet connectors. (these wires are White with red stripe and White with green stripe)
The new sensor will also be completely encapsulated so rusting should be a thing of the past once installed.

Weather this will resolve your issue that is another issue.


If engine starts and runs, typically it is NOT the sensor.

You need a timing light, connect, run boat on lake (two people). Watch timing mark, at idle it should be around 8* BTDC.
Once you get close to 2000 rpm it should be moving high to say 18-20 degrees BTDC. If the timing mark stands still and does not advance then most likely it is the timing control module.

BUT, I would suggest replacing the sensor first as a preventative measure due to corrosion.

Retest

If results are still bad then replace timing module (module is typically located on Exhaust manifold small black box with wires)
 
Re:.... sensor... clean it for the balance of season... Consider a new one for next year. T'bolt caps/rotors (in a salt water enviro) good for 2 seasons trouble free at best. That vent is a USCG requirement, however it causes the disti to breath in "salty air" with daily temperature changes. Replacing T'bolt rotors is a bit tricky... hard to get off and it you didn't CAREFULLY mark the orientation of the rotor on the disti base carefully BEFORE you removed the rotor, (and record the height!!) getting the new on on is....interesting .... as some have a VERY tight fit and there is no adjusting to get it to seat properly.
 
sandkicker said:
Re:.... sensor... clean it for the balance of season... Consider a new one for next year. T'bolt caps/rotors (in a salt water enviro) good for 2 seasons trouble free at best. That vent is a USCG requirement, however it causes the disti to breath in "salty air" with daily temperature changes. Replacing T'bolt rotors is a bit tricky... hard to get off and it you didn't CAREFULLY mark the orientation of the rotor on the disti base carefully BEFORE you removed the rotor, (and record the height!!) getting the new on on is....interesting .... as some have a VERY tight fit and there is no adjusting to get it to seat properly.
Click to expand...

There is no cleaning of this sensor. If it is rusted, the areas of rust may impact the circuits/solder. I would not recommend touching anything unless replacing.
 
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