Power Pack output test

[FSUDTD]

Good evening friends,<br /><br />I posted a while back thinking i may have dropped a cylinder in my '88 40hp johnson; after checking the compression (120-115) im continuing the search for my problem. Went out one day with the engine running rough at WOT, and on the final decsent home (not very far) it cut to half speed and bogged down. tinkered with it and charged the battery and tried it two weeks later; started up and idled fine, but again, right off the bat bogged down at WOT. If it got on plane all day it was not for 5 seconds before it would cut out. Have done some preliminary checks on the fuel system: the fuel pump looks to be pumping gas sufficiently and the carbs look to be in really clean shape. To get to my point, i want to test my power pack to see if it may be the culprit; I tried one test i read in Clymers by using a voltage meter and sticking the positive probe up in the boot of the leads coming from the power pack. supposedly if i get anything less than 200 volts the power pack is toast; i got maybe 20 volts. Anyone know of any other tests that are easily done by a novice or any other suggestions as to what my problem may be? <br /><br />Thanks so much

 

[OBJ]

Re: Power Pack output test

Look for spark on each cylinder and find which one is nada. Swap the coil leads and see if the problem follows or stays the same. If the problem follows, power pack is probably gone. If the problem stays with the cylinder, the coil is most likely done.

 

[FSUDTD]

Re: Power Pack output test

obj, <br /><br />if the power pack is gone, will one of the cylinders be without spark? i have tested the spark (in the driveway on the muffs) and both cylinders seem to have sufficient spark, but again, it idles fine and starts right up every time, so maybe the spark declines under load.<br /><br />thanks for the response!!!

 

[Xcusme]

Re: Power Pack output test

FSUDTD,<br />Have you tested to see if the motor is overheating? Are you sure you backprobed the right wires when you tested using the meter?? 20 Volts doesn't sound right.

 

[OBJ]

Re: Power Pack output test

It's curious but I had a similar problem on a crossflow 90hp just yesterday. With the spark tester connected, I had what appeared to be good spark on all cylinders. Crank the engine up and #2 and4 cylinders would not fire. Checked all connections and retested with spark tester....showed good. Recrank engine and I lose spark to the same cylinders.<br /><br />Swapped out the power pack for 2 & 4 cylinders and started the engine, run like a dream.<br /><br />I'm not familiar with the tests in Clymers. But like Xcusme said, 20V don't sound right. Were you using a peak reading volt meter? Check your Clymers again and see if they specify a peak reading meter.

 

[FSUDTD]

Re: Power Pack output test

Well, I must confess that Ive decided to take it to the dealer and let them sort it out. Whereas I think it is something that we could figure out eventually, Im not willing to give up that much of my fishing season to do it. Water temp just reached about 68 degrees, so you know what that means.... cobia. I will, however let yall know what ends up being the culprit. Thanks for all your input anyhow, I really appreciate it.