7.4 GI Cutting Out... Help a Newb

Matt4570

Recruit
Joined
Jun 2, 2017
Messages
2
Greetings Iboaters. I'm hoping someone can assist with ideas on a power loss/cut out issue I'm having with my Pursuit 2860. Equipment: VP 7.4 GI PBYCCE, DP outdrive. I'm experiencing a momentary (maybe 1/2 a second) loss of power once the engine is at approx 3K rpm and up. Basically once the engine is at operating temp, then completely randomly, there is an abrupt but very short total loss of power from the motor. Almost as if you pulled the lanyard but reinserted so quickly that the motor didn't die. Once the problem occurs it will reoccur within a minute or may wait for 5 or ten. Otherwise the motor runs great, no missing or stumbling and great power. So far I've replaced all of the ignition components (coil, coil pickup, module, cap, rotor, plugs, wires), kill switch, fuel pumps, batteries, checked grounds and elec connnections. Fuel system checks out, as stated pumps replaced gas is good and the tanks are clean. I read about faulty or corroded tachs causing similar problems in Mercruiser 7.4s and unhooked mine but no change. I finally gave up and called in a pro but he's stumped too. I guess the only things left are relays and ecm? Am I missing anything?
 

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
18,452
Fuel pressure regulator. . . Ignition control module. . . ECM connections. One thing you might have to do is connect the diagnostic computer and actually run the boat in the water and see what the data tells about the power interruption.
 

Silverbullet555

Chief Petty Officer
Joined
Mar 13, 2011
Messages
621
As Ted said, you need data logging, either on your own or with tech. Then, you'll be able to see what's going on.

Intermittent is tough.
 

Matt4570

Recruit
Joined
Jun 2, 2017
Messages
2
Thanks for the replies. I failed to mention that both the fuel pressure regulator and ICM are new. The tech checked all connections and data logged on Wednesday. Found a 6V drop to the coil during the interrupt but so quick that he couldn't determine a cause. We will try it again tomorrow after replacing a relay. Fingers crossed.
 

Silverbullet555

Chief Petty Officer
Joined
Mar 13, 2011
Messages
621
Thanks for the replies. I failed to mention that both the fuel pressure regulator and ICM are new. The tech checked all connections and data logged on Wednesday. Found a 6V drop to the coil during the interrupt but so quick that he couldn't determine a cause. We will try it again tomorrow after replacing a relay. Fingers crossed.

Well, that data is seriously valuable. You've eliminated many things and can focus on finding out why you are losing voltage.
 
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