Johnson 48 compression

[5string]

I checked the compression, cold motor, I just pulled the spark plug wires and then pulled one plug at a time. I cranked it about 5 seconds, until it didn't go up anymore and I got about 138 on each one. Just need to know what it should be. If this is good then I have to figure out what might be next as far as not getting the power I had before. I may need to weigh the boat somehow to see if the foam is full of water even though I have left out the plugs for several weeks. It is an 18 foot Polar Skiff and I spoke with a guy from the company and he says he has only seen one boat with waterlogged foam so he doubts that is the problem and he claims the foam shouldn't hold water that the older boats had the wrong foam and a 96 year model should be good.

5string in NC

 

[tashasdaddy]

Re: Johnson 48 compression

compression is like new. was any work done prior to you loosing power? have you check spark with a spark tester? should jump 7/`16 " arc. using new fuel? did the motor set for a while, prior to the problem?

 

[JB]

Re: Johnson 48 compression

Compression testing should be done with all plugs out, 5string. You got very good numbers but you put unneccessary load on the starter.

Please describe the events/symptoms that caused you to say you have lost some power.

40

 

[5string]

Re: Johnson 48 compression

I don't understand, aren't both plugs in when you start it? How does leaving one in when testing the other one strain the starter? I only cranked for a few seconds till the gauge stopped rising. I'm not sure why the boat doesn't plane like it used to, I may just carry it to the repair guy and let him figure it out. I'm going to get a tachometer and get on the water and run it some first to see if I can determine anything and take it from there. Thanks for the help.

5string in NC

 

[kenmyfam]

Re: Johnson 48 compression

I don't understand, aren't both plugs in when you start it? How does leaving one in when testing the other one strain the starter? I only cranked for a few seconds till the gauge stopped rising. I'm not sure why the boat doesn't plane like it used to, I may just carry it to the repair guy and let him figure it out. I'm going to get a tachometer and get on the water and run it some first to see if I can determine anything and take it from there. Thanks for the help.

5string in NC

Good idea to take it for a run again to get some more input. Do that first and report your findings here before you think about taking it to a repair shop.