How do you test a powerpack?????

[cvlngineer]

Before I turn my wallet inside-out, how can you tell for certain the the thing is going out?<br /><br />It is installed on a 1975 Johnson 70 hp.<br /><br />Thanks,<br />cvlngineer

 

[dick]

Re: How do you test a powerpack?????

Well what is wrong?

 

[cvlngineer]

Re: How do you test a powerpack?????

The motor bogs down when I am trying to accelerate. Once I get a little momentum, it is like someone flips a switch and it takes off fine. I can not drive the boat up on the trailer. I have rebuilt the carbs, swapped out coils, ob synched the carbs, I put in a new thermostat. It still has the same problem, I even gave it a real good cussing this afternoon, but that didn't work either. <br /><br />Thanks,<br />cvlngineer

 

[SCO]

Re: How do you test a powerpack?????

Civil, Ive seen a powerpack failure, and maybe it is different every time, but here is what happened. I was running at cruise, then boat started slowing, added more throttle. After a while the boat came off plane and I couldnt get it back on. Limped back in then got a genuine OMC pack which is now some 3 years old. Problem solved. There were prior symptoms. When I started the motor, I would have to get to some 2000 rpm, then it would switch , like a light switch, to all four cyl., even when warmed up. There is no transition on the motor related to rpm with the new omc pack. Check my recent post about idle and start. I bet it is jet, carburation related. I am going to immerse soak the carbs this time, to clean.<br /><br /> I get the same symptom as you when I idle for a period of time. The bog that is.

 

[cvlngineer]

Re: How do you test a powerpack?????

SCO,<br /><br />I don't know what to think about mine. I have had the carbs off and all passageways were clear. I can't get my boat up the trailer, no matter what I try. It does what you described earlier in your post, once I reach a certain rpm, it is like a light switch, then it accelerates fine. The motor starts and idles fine at all temperatures.<br /><br />Thanks,<br />cvlngineer

 

[ajp]

Re: How do you test a powerpack?????

We have a 1980 70hp Johnson that for years has died when you give full throttle too fast. Idles all day, if you baby it a little to full speed it works great.<br />I have been told:<br />compression<br />carbs<br />you name it. <br /><br />The test I would run is to choke it a little when you give it full throttle. If that cures the problem you know it is starvig for gas. I had that problem on a 115hp and opened the low speed idle jets a little and fixed the problem. I doubt it is a powerpack problem. <br /><br />I think it is related to old engines that are wore out. They start having less and less compression, leaf reeds that don't work well, and clogged jets in the carbs. When you said the carb passages were clean, did you remove all the carb plugs to see the minute passageways and fixed high and low speed jets. <br /><br />I think if you can solve this problem you would make alot of fisherman happy.

 

[cvlngineer]

Re: How do you test a powerpack?????

ajp,<br /><br />I removed all the screws and ran a fine piece of soft wire through all of the jets, and they were clear. I then sprayed carb cleaner through them to verify that they were open.<br /><br />I checked compression, and all were right at 120 psi. I think I will put it in a barrel of water and get a timing light to verify that I am getting fire on all cylinders during the bogging, if I can get it to bog in the barrel (without throwing all of the water out!)<br /><br />I will report back anything I discover.<br /><br />Thanks,<br />cvlngineer

 

[Walker]

Re: How do you test a powerpack?????

Are you still haveing problems with it? If you only sprayed carb cleaner thru the carbs, that is not good enough. Go to the auto parts and get a gallon of Chemtool B12 soak. It has a wire basket in the can too. Tear your carbs down and soak them one at a time for at least 20 minutes. Then spray them off with spray carb cleaner and blow them out with compressed air. Did you put new plugs in yet??

 

[Hooty]

Re: How do you test a powerpack?????

The Clymer and OMC manuals that I have all have specs for testing power packs. Do you have a manual?<br /><br />c/6<br /><br />Hooty

 

[ajp]

Re: How do you test a powerpack?????

Civlngineer,<br /><br />I believe that those carbs have plugs that you can drill out to expose the jets inside the carbs. If one of the carbs is not working up with the others, you can have that type of problem. <br /><br />When I say plugs, they are lead plugs that open up passageways in the carbs. Each carb has 2 or more plugs. I think each carb has a fixed high speed and low speed jet. <br /><br />I would get a "factory" service manual.

 

[SCO]

Re: How do you test a powerpack?????

civil, I missed the part in your post about the light switch. It does sound more like what I experienced. Can you borrow a pack and test?. The one that failed for me was aftermarket and brand spanking new. Be careful, I think it may have big capacitors that can kill.