Fuel Solenoid check for Low Power issue 6TBA 370hp

[Mike Uliasz]

Been reading thru LOW POWER / LOW RPM AND NO DARK SMOKE trouble shooting steps. Looking for guidance on next steps.

The fuel solenoids on both my engines are staying fully extended at full throttle (motor off). I can push the solenoid into the retracted position by hand. Had mechanic inspect the engines at purchase, said throttle cables are stretched and it was not hitting WOT.

Should fuel solenoid retract the fuel level incrementally as the throttles are pushed forward? Find it weird the same issue on both motors. Hope I’m reading the write-up correctly.

Here’s some info on the motors.

1) Tachs have been checked for accuracy at the dock in neutral – 1500 = 1518, 2000 = 2060 & just under 3000 = 3038, so ~50 under

2) No load RPM WOT at the dock? 3000 RPMs for both motors, one motor did hit 3300 RPMS after purchase prior to replacing a wore out cable mounting clip.

3) Throttle levers on the injection pump hit the stops? No, according to mechanic (stretch throttle cables). Could this cause the fuel solenoid not to fully retract? I’m not exactly sure where the stops are.

4) No dark or grey smoke other than a touch if I throttle up quick to a plane. WOT 2800 RPM’s now. Had props tuned from 23 x 26 – 7 cup to 23 x 24 – 7 cup during the winter since, WOT was 2600 RPM’s.

5) Aftercoolers service done July, 2019 SBMAR kits
6) Both engines were rebuilt by prior owner 2013 (aftercooler failure) & 2017 (not sure) ~1160 hours. P

pic 1 & 2 port engine, 3 & 4 SB. 45408232 & 45407742

Thanks

Topic

[Mike Uliasz]

Rob,
Thanks. Read the Fuel Shutoff Solenoid Wiring 101 writeup and its making sense. Answer’s my question and another question when we were having issues starting the motor after the raw water pump/fuel cooler removal. My buddy ended up grounding the Fuel Shutoff Solenoid like mentioned in the article after reinstalling.

So next question ‘throttles up to the stops’ or ‘throttles not hitting the stops’. I’m lost on where the ‘stops’ are to check this.

Thinking that’s my next step, and if not hitting the stops, get the throttle linkage right, Then check WOT under no load and go from there. Appreciate your patience.

Going to be at the boat Thursday for a solid week so hoping to make some progress.
THANKS again

[Rob Schepis]

No load is low. Those engines should make close to 3,400 no load. It’s on the spec sheet: min 3,300, max 3,400.

The position of your throttles and what the fuel solenoids are doing are independent of one another. The fuel shutoff solenoid is only controlled by the harness it is plugged into. If you goto Tony’s Tips and search “solenoid” you’ll get plenty of useful hits. Here’s a few:

https://www.sbmar.com/articles/fuel-shutoff-solenoid-wiring-101/

https://www.sbmar.com/articles/how-the-cummins-bosch-p7100-injection-pump-solenoid-works/

https://www.sbmar.com/articles/how-to-test-your-marine-bosch-fuel-shutoff-solenoid/

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Mike Uliasz

[Mike Uliasz]

attached pics, sorry so close but not much room to work with

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