Mercury elpto 75 cdm intermittent spark

kamil79

Recruit
Joined
Jun 6, 2016
Messages
3
Hi guys!
Got problem with 75 merc cdm ignition .
Engine start easily, but working bad under load, missfire, drop cyl trying wot. When boat is on the plane pulls good middle range, but when i try max speed it feels like something hold the engine.
I noticed that i hook up timig light to second cyl
it sometimes got rare black spots and intermittent no spark (its cover with engine behavior) Got spares cdms but change doesnt resolve the issue.
​​
 

tommarvin

Ensign
Joined
Nov 22, 2015
Messages
999
Motor starts easily , when boat is on the plane pulls good middle range, so good so far,
When you try wide open throttle something is holding the engine from WOT.
She could be starved for gas,or there is an ignition problem and you need to start testing ignition parts, but first are you willing to bet your life the fuel system is perfectly clean,fresh gas, carbs or EFI lots to clean with EFI.
CDIelectronics.com will explain how to test ignition parts just like you tube.
Clean your carbs or your fuel injectors replace old filter on the end of injector. fuel filters everything
 

kamil79

Recruit
Joined
Jun 6, 2016
Messages
3
I changed the fuel line, rebuild carb, new fuel pump kit, new sparks. Primer bulb is stiff and pumping doesnt change anything. Link and sync made 100 times. Pushing choke overflow engine, think is no fuel related.
Spark gap looks good, jump 7/16,.
Changed trigger to used one and still engine shaking under load, drop the cyl. Sometimes it behaves smooth for little time, then again start random missfire.
Comresion 125-130 psi
Timing light show bearly noticable breaks in spark on second cyl. Got 3 spare cdms ,but change 2 cyl cdm doesnt resolve the issue. Engine behaves the same with regulator and handle disconected.
My ideas are end, could be defective engine harness? Could defective stator influence on only one cdm? Sorry for langugae iam writig from Poland, and all mechanics tell me to buy 4 stroke :)
 

kamil79

Recruit
Joined
Jun 6, 2016
Messages
3
Yes ,new plugs, still intermittent drop cyl under load. I must put boat on trailer and check all wiring harness for bad ground or broken (melted) wires.
 
Top