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Ask Dominick Your Own Question
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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I have twin 2002 yamaha ox66 250's. Thought i had an ethanol

Customer Question

I have twin 2002 yamaha ox66 250's. Thought i had an ethanol prob;em so changed/cleaned all filters, o2 sensor, and injectors. engine still wont go over 3000 rpm. tested for spark and have none on one side of the motor. after reading alot, i think i have a grounding problem on the side not firing. am looking for a wiring diagram to trace the ground wire so I can test. If the grounding isnt the issue, then i think i need a new CDI. Just want to make sure it is a grounding issue and not the cdi
Submitted: 2 years ago.
Category: Boat
Expert:  Jason replied 2 years ago.
Hello my name is ***** ***** am I speaking with?
Does the alarm system work on the engine? If you remove the lanyard and then turn the key, does it beep?
Customer: replied 2 years ago.
havent had an alarm go off. havent tried removing the lanyard
Customer: replied 2 years ago.
my name is jim
Expert:  Jason replied 2 years ago.
Hi Jim. Yank the lanyard and try to start it, does the alarm sound or is there nothing?Are you in front of the engine now?
Customer: replied 2 years ago.
not at the boat now. Can try when i get off work. Will try what you suggest. Where do I go in either case
Expert:  Jason replied 2 years ago.
If the alarm isn't going off (it should) then chances are you have an alarm issue and you just don't know it because of a bad beeper. Does that make sense?
Customer: replied 2 years ago.
Im sure that three of the 6 cylinders do not have spark, all on the same side. How would the alarm cause 3 cylinders to not fire?
Expert:  Jason replied 2 years ago.
If the engine is overheating or low on oil. Or thinks it is because a sensor is bad. It is going to go into power reduction and cut spark to the engine in order to limit rpms.
Customer: replied 2 years ago.
ok. I have good water coming out of the tell tale and have never let it run low on oil. what sensor would i need to check/test and where is it on the motor? When it goes into power reduction it cuts off all three on one side?
Expert:  Jason replied 2 years ago.
This would be easier if you were in front of the engine, it keeps us from playing the "what if" game. Can you find out if the alarm sounds when you pull the lanyard first, and then let me know?
Customer: replied 2 years ago.
Will have to try you back tomorrow or the next day. Storms coming to the chesapeake this evening so i might not get to test the lanyard tonight. So i need to try to start the engine without the lanyard, if it sounds the alarm then its not the alarm and maybe something else. What do you think of my grounding hypothesis?
Expert:  Jason replied 2 years ago.
Correct. On the grounding hypothesis, honestly it's not likely. Let me know what happens and we can take it from there.-Jason
Customer: replied 2 years ago.
Expert:  Jason replied 2 years ago.
You bet
Customer: replied 2 years ago.
I tried to start the motor with the lanyard out and the alarm did sound. Whats next? BTW, i pulled the boat yesterday for bottom paint so it is now on land.
Expert:  Jason replied 2 years ago.
Pull the engine cover and locate the shift linkage on the engine the linkage is a shift shift. Unplug it, and then hook your meter up to it and see if there is continuity across the switch, and see if that breaks when you shift it back and forth.
Customer: replied 2 years ago.
Will try to get to it tonight. Thanks.
Expert:  Jason replied 2 years ago.
Keep me posted.

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