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Dominick
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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1996 MERC 150 EFI. TACK NOT READING CORRECT.HAVE REPLACED BOTH

Customer Question

1996 MERC 150 EFI. TACK NOT READING CORRECT.HAVE REPLACED BOTH VOLT REG'S. STILL ON GOOD. ALSO NO POWER. WOT THE BOAT FEELS LIKE I AM PULLING A CAR, THEN IT FEELS LIKE 3 MORE CYLINDERS KICK IN AND THE BOAT TAKES OFF.SWITCH BOX? INJECTORS? HELP
Submitted: 1 year ago.
Category: Boat
Expert:  Jeff G. replied 1 year ago.
Welcome,this question may need more than a single answer. Please post back with additional questions on this at any time.
OK can you do some voltage tests?
Check battery voltage should be 12.5 volts. Start and run engine at 1000 rpm, voltage should raise to 14.5 volts.
The tach runs off the alternator side of the stator so checking the voltage is a quick easy test.
Customer: replied 1 year ago.
voltage is ok
Customer: replied 1 year ago.
idle is rough, fuel pressure is good. show spark @ all COILS.
Expert:  Jeff G. replied 1 year ago.
Did you just check it?
Check the tach circuit put the black meter lead to the case of each voltage regulator put the red meter lead to the gray wire with all the wires disconnected. Check the resistance, what do you get?
Customer: replied 1 year ago.
RX1K 13000
Customer: replied 1 year ago.
ENGINE IDLE 750 RPM TACK SHOWS 2200 AND IS NOT STEADY. WHAT ABOUT THE POWER PROBLEM???
Customer: replied 1 year ago.
CHECKED STATTOR, AND TRIGGER. BOTH TEST IN RANGE.
Customer: replied 1 year ago.
HOW WE DOING?
Expert:  Jeff G. replied 1 year ago.
If the voltage is good and the tach circuit checks OK then the tach is the problem. If the voltage is too high or too low, either one it will effect the rest of the engine as your engine is controlled by the ECU.
You say you have good spark at cranking. So I want you to check the spark at speed. To do this we will need to use an inductive timing light. Run the engine and when it acts up put the timing light on the top right #1 cylinder. Watch the flashes, we aren't watching the timing, rather the flashes, then repeat on the other cylinders.
Your engine has a high speed and low speed circuit, we need to check both.
Disconnect the tach and see if the engine performance improves.
Customer: replied 1 year ago.
I WILL NEED TO PUT BOAT IN THE WATER AND FIND ANOTHER PERSON TO HELP. HOW DO I GET HOLD OF YOU WHEN I HAVE COMPLETED WHAT YOU ASK? IF I UNDERSTAND YOU WANT ME TO MAKE SURE I HAVE SPARK IN ALL CYLINDERS WHEN I GO TO WOT.
Expert:  Jeff G. replied 1 year ago.
Yes, your ignition system has a low speed and high speed circuit we need to check both. All you have to do is to bookmark this page and then when you are ready to post back here and then we can continue on. Easy!
Customer: replied 1 year ago.
THANKS. I WILL POST BACK WITH THE RESULTS.
Expert:  Jeff G. replied 1 year ago.
Great!

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