88 Johnson 25hp blues

[Need2fish]

My 25hp johnson won't idle, is hard to start and won't plane my boat out.(14 foot jon boat)<br />The trouble started all at once.<br />I've checked the coils w/ ohmmeter, replace plugs, powerpack(not cheap for this year), rebuilt fuel pump,(although it seems to be getting fuel just fine).<br />All this started last year so I have been using another motor and working on this one from time to time. <br />I took it out one time last fall after checking the carb(which was clean as a pin) It did the same old stuff, so I cut it off and fished a little. When I went to start it again It ran like a scalded dog!! About 10 seconds later I noticed that the water pump wasn't working, so I shut it down. After It cooled A little, I tryed to start it up again, but it would just idle rough then die. But it started pumping water again. <br />After this I replaced water pump and power pack and took it out again, but I just runs along slowly with the bow in the air.<br />Could my head gasket be blown??

 

[Allan19603hp]

Re: 88 Johnson 25hp blues

Sounds to me like a head gasket. I would come to this conclusion because of the overheating and the poor idle problem along with the loss of power, I would try the head gasket for sure. Sorry to hear you had to buy one of them packs, but they are handy to have as a spare. LEt me know if you need more help.<br /><br />ALlan

 

[JB]

Re: 88 Johnson 25hp blues

Howdy, Need 2...<br />Before you start buying more parts that you don't need, let's isolate where the problem is.<br /><br />1. Is it a fuel starvation problem? Pump your primer bulb while the engine is misbehaving. If the engine picks right up, you have a fuel delivery problem.<br /><br />2. Is it running on 1 cylinder? pull each plug wire while it is idling. If the engine rpm drops or the engine dies, that is a good cylinder. If there is no change, that is a cylinder that is not making power.<br /><br />3. It is running on one. Is it an ignition problem? Hold the plug wire about 1/2 to 3/4" from the block. Does it make an arc?<br /><br />4. It has spark on both, both are making some power, but not enough. Is it a compression problem? Check compression with the plugs out. Both cylinders should compress 90psi or better and be within 15% of each other.<br /><br />5.Compression on one bad. Pull the head and inspect head gasket and cylinder walls.<br /><br />Good luck.