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KFJCARLOS
03-16-09, 07:44 PM
I have a problem with my jetboat, mercury 240, 6 cyl. Fuel injection, when the boat is out the water the revolutions is up to 7000 and in the water the revolution are 4000 or less. I change the gasoline pump brand new, fuel filter new, spare new. Please tell me what i do.

rookie101
03-16-09, 07:59 PM
Start with a compression test and go from there. You want to see 115-120 Min per cylinder.


Aaron

KFJCARLOS
03-16-09, 08:03 PM
I do it and it have 135 per cylinder

rookie101
03-16-09, 08:11 PM
Make sure your throttle cable is adjusted properly and that you are really getting full throttle. After that rent a fuel pressure gauge from an auto parts store and make sure you have 34-36 psi of fuel pressure at all times.

Also any time your plugs are more than a year old in a two stroke just replace them with new ones no matter what they look like.

Aaron

KFJCARLOS
03-16-09, 08:24 PM
Thank you for your attention, the mechanic check the fuel pressure and it is in 38 psi, i will check the throttle in the weekend and i let you know.

Do you have another idea about the problem?
Today somebody tell me that i have to check the temperature sensor, what do you think about that?

rookie101
03-16-09, 08:56 PM
Temp sensor affects 1/2 throttle and below. At Idle if it is shorted it will increase fuel flow by up too 40%, but will not affect full throttle. I have seen other members have an issue with coils that break down under load. The only real way to check them other than replacing them is to do a resistance check.

Looking at the coil connector (coil side with the lock tab up)

A black

B black/yellow

C white

D green


On the first four tests have your meter set on Diode. On all tests place the negative lead on the first letter and the positive lead on the second letter.


D-B CONTINUITY

B-D OPEN (NO CONTINUITY)

D-A OPEN (NO CONTINUITY)

A-D CONTINUITY

A-C 1000-1250 OHMS

A-SPARK PLUG LEAD 1000-1250 OHMS


If one of the coils (capacitor discharge module) is shorted it will shut down two cylinders, as they receive their ground path through each other.


Aaron:cheers:

KFJCARLOS
03-16-09, 09:13 PM
:)thanks i will check and let you know

KFJCARLOS
03-22-09, 07:15 PM
HI, JUST TO SAY THANKS ABOUT YOUR COMMENTS, I CHANGE THE TEMP SENSOR AND NOW THE BOAT IS RUNNING SO GOOOOOOD . I WAS SO HAPPY:hurray::cheers:

rookie101
03-22-09, 08:48 PM
Good to hear.:hurray:

Thank you for the update.

KFJCARLOS
03-30-09, 08:55 PM
Yesterday i used my jet boat again and i didn't hear the beep of the sensor when i turned it on, and begin with the problem again.

KFJCARLOS
03-30-09, 08:57 PM
I need the repair manual, where i will found it?

seadoosnipe
03-30-09, 10:40 PM
With the victory on March 22nd, then back to square one again, I think it's safe to say you have a short somewhere. Likely in the temp sensor, since you saw a temporary repair in this.

The first thing I'd do here is check the sensor for a good ground. Since the sensor's ground is the block, make sure the threads are clean, no oil build-up on the sensor or head. Make sure there is no type insulation keeping it from a good ground.

You can test this system by starting the engine. While it is running, disconnect the wire to the sensor. If there is no change in engine RPM, then your temp sensor is either bad or shorted.

There are also other sensors on the 240 hp EFI that could cause the RPM problem.

The MAP (manifold absolute pressure) sensor. There is a vacuum hose that connects this sensor to the intake manifold. Make sure it is connected.

The air temperature sensor. This sensor affects the throttle by enriching or leaning out the fuel in direct relation to ambient temperature. If it detects a colder temp, it adds fuel. If it detects hotter temps, it leans the fuel system out.

One last thing you need to check is battery voltage. The EFI (electronic fuel injection) system needs a ready supply of proper voltage to operate correctly. Use a multi purpose tester to ensure your charging system is sending 13.5 to 14 VDC to your battery while the engine is running.

We do have the shop manual for the 240 EFI in our library, available with a "premium" membership........

Working with Rookie101, you will get your motor running. Just be patient and work with all the possible scenarios that may be causing this gremlin. You'll find it, I'm sure.:cheers:

rookie101
03-30-09, 11:53 PM
KFJCARLOS give the things Seadoosnipe mentioned a try as well as checking all your grounds, including checking between the battery and the engine itself with a multimeter. When you run your leads between the negative post on the battery (with it hooked up and the switch in the on position) and the engine block you should have almost perfect continuity, or 0 ohms.

Aaron:cheers: