Compression test? 240 EFI Mercury M2 GEN. 1.

[rsatina2002]

Hello everyone, I would like to know how to properly do a compression test on M2 240 EFI engine GEN. 1? I did mine on a cold engine and compression results are low but very uniformed.... On the starboard side of cylinder 1, 3, 5 it is 120 PSI all of them, and on the port side of cylinder 2, 4, 6 it is 110 PSI all of them. ? I know the numbers are a little low, give me suggestions what to do? It is time to rebuild it or just apply some cylinder and injector cleaners to improve cylinder compression? Your input is highly appreciated. Thanks.

 

[Tim75]

Hello everyone, I would like to know how to properly do a compression test on M2 240 EFI engine GEN. 1? I did mine on a cold engine and compression results are low but very uniformed.... On the starboard side of cylinder 1, 3, 5 it is 120 PSI all of them, and on the port side of cylinder 2, 4, 6 it is 110 PSI all of them. ? I know the numbers are a little low, give me suggestions what to do? It is time to rebuild it or just apply some cylinder and injector cleaners to improve cylinder compression? Your input is highly appreciated. Thanks.

Use extreme caution!
Turn on bilge blower.

Connect a good battery charger.
Remove all the spark plugs.
Key off! Advance throttle to full WOT.
Connect gauge to your favorite spark plug hole.
Use a mechanic test switch, connect to red battery cable and small terminal on the starter solenoid (starboard side).
Press the button, until pressure stops increasing on the gauge about 4 or five revolutions.
Record the pressure and cyl #. Port 1,2,3;Starboard 1,2,3.
Move the gauge to next hole and repeat.

The best single thing I personally ever did to improve performance and decrease fuel consumption was fuel injector clean, sevice and calibrate. Expect about $120- $200 for all six.

 

[rsatina2002]

Thanks Tim, I got it, what I did is just simply remove all spark plugs, remove 3A fuse for fuel sender/primer pump, and starts the engine using the key while watching the gauge to the highest PSI record on each cylinder. Thank you for your suggestions of cleaing the fuel injector. I might do it myself if it really, not getting the power of acceleration when testing on the lake in california.

 

[Tim75]

Thanks Tim, I got it, what I did is just simply remove all spark plugs, remove 3A fuse for fuel sender/primer pump, and starts the engine using the key while watching the gauge to the highest PSI record on each cylinder. Thank you for your suggestions of cleaing the fuel injector. I might do it myself if it really, not getting the power of acceleration when testing on the lake in california.

You can try, but unless you have a flow bench and are experienced repairing Keihin injectors, I don't think you will have much success. It was well worth the expense.
My engine almost always starts in under 5 seconds. Very little smoke.

 

[Dr Honda]

I agree with Tim. Injector rebuilds are a pain... and normally it's cheap to have done. normally around $100 and a reputable shop.

Your compression numbers are a little low, (I would like to see 125psi) but since we don't have any history on that gauge... I would check it with an air compressor and a known good gauge.

 

[rsatina2002]

Hello good news for my 2002 sea doo challenger 240 EFI, I did change the air temp sensors, and it doesn't have any hot start problem anymore. We just went fishing fall day last weekend here in newport beach ca and caught some fish my lowrance 7" fish finder was doing well. I did install it myself and the boat is running well with good idle at 1,200-1,300 with load and no hard hot starts and boat is in storage now ready for the summer next year. Im not going to winterized it i'll just put a fuel sta-bil and start the engine once every 4 weeks to let it keep running.... California don't have a snowy winter so it can go to the beach anytime, weather permitted. Just sharing it to all of you, I did check all the sensors and hopefully no major problems coming up and set the TPS to 2.4 volts at idle and everything is working good and no leaks. Thanks Dr. Honda for your help but definitely need your advice next time I have a problem on my Sea Doo. The project that i have now is my newly acquired jetski a 2001 Yamaha XL-700 waverunner, it's only $500 it is not running but I guess it is easy to do it than repairing my 240 EFI engine from the scratch. Wish me luck for my new yamaha ski.

 

[Dr Honda]

That's good news... and you are fine in SoCal without a winterazation. BUT... I would still do a "Winter" maintenance. Basically.... drain and refill the gear box, just to make sure it's clean and there's no water in it. (A little can get past the seals)

FYI... I lived in SoCal most of my young life, and "Winterizing" was that month or 2 you needed a wetsuit. AND... the 700 Yamaha engine is probably the best engine they produced. Make a post in the non-Seadoo section and we can work through it.