1998 johnson 25

[justen00]

hi new to the forums, having a problem with my motor, its a 98 johnson 25 tiller, it has been running fine until one day i mixed the oil a little strong, it fouled the plugs changed them and, now when i run it, it will run wide open for a short amount of time then just bogs down, it surges at about half throttle then sometimes will pick back up and run wot until i let off then repeats the problem again, and it seems to keep fouling the top plug out, im lost ive cleaned the carb and it looks spotless everytime i pull it apart, any help would be greatly appreaciated, thanks in advanced everyone.

 

[jbjennings]

Re: 1998 johnson 25

The surging sounds like a coil going out. It could also be starving for fuel. Take the fuel line off and see if there's plenty of fuel coming out when you squeeze the primer bulb. I've had bad check valves in the primer bulb, a split in the fuel pickup inside the tank, leaking fuel line connectors.......
Find out about spark and fuel. One or the other. When it does this surging thing, you could try taking off one plug wire and seeng if it runs. Then trying the other. If taking off one plug wire kills it, then you don't have spark on the other wire.
Good luck,
JBJ

 

[steelespike]

Re: 1998 johnson 25

I suspect weak ignition probably one cylinder.If you check the old plugs the top one is probably worse.With modern ignition over oiling isn't likely to cause fouling.
Even at 16:1. It would probably run the season.
Poor mans way to check the coils is to switch them and see if the fouling follows.

 

[boobie]

Re: 1998 johnson 25

You may want to go to a local parts house and buy an adjustable open air gap spark tester for around $8.00. Set it at 7/16 " open air gap and check your spark and then you'll know what you have.

 

[justen00]

Re: 1998 johnson 25

thanks everyone so much i just bought a whole new tank and hose set up, same results so im just going to order two new coils, as soon they come in the mail ill let put them on and let you guys know.

 

[Haffiman]

Re: 1998 johnson 25

Remove the fuel pump with hoses attached.
Squeeze the bulb and see if any fuel leaks out the pulse hole at the back.
If so, re-build he pump or change.

 

[justen00]

Re: 1998 johnson 25

hey everyone i checked the fuel pump it was working good, i got 2 new coils plugs and wires everything was good, it seems like its getting good spark and fuel, took it out hunting this morning and it was cold down here (central florida) to me anyway lol, it ran perfect for about a mile, and then back to the same ol routine, it seems like when it gets warm it acts up? i placed my hand over the top cylinder on the head and its warm but not burning hot did the same thing to the bottom one and it felt the same. any suggestions on what next i called a marine mechanic place and they quoted me 150$ for a diagnostics didnt really want to spend that kind of money just to find the prob. any and all help will be appreaciated thanks

 

[justen00]

Re: 1998 johnson 25

just an update i checked the compression it was 105 on both cylinders, so i have no clue what else to do, any suggestions?

 

[jasper60103]

Re: 1998 johnson 25

just an update i checked the compression it was 105 on both cylinders, so i have no clue what else to do, any suggestions?

Well, that's good news on the compression. Is the top plug still fouling out?

 

[justen00]

Re: 1998 johnson 25

yeah its still fowling it out, one thing im not sure about is there is a wire that goes right into the head on the top cylinder not sure what it is but i guess the guy i bought the motor from had removed it at some point because it has silicon all around it, would that have comething to do with the top plug fouling that wire goes to the power pack

 

[justen00]

Re: 1998 johnson 25

excuse me for my ignorance guys but could this be happening because my oil mixture is to lean or rich? took 0the boat out this morning just to see and it does the same thing runs for a couple of mins then back to the surging thing at half throttle and just holds maybe 2500 rpms at full throttle,(2500 rpms is a guess i have no tach). let it sit and cool down and it will run good for a little while and then back to it aigain?

 

[outlaw241]

Re: 1998 johnson 25

i think that wire goes to the thermos stat, sounds like a overheating issue,time for a new water pump impeller an make sure your upper water tube grommet is in good shape.

 

[justen00]

Re: 1998 johnson 25

i forgot to mention that the impeller is is about 4 months old, changed it when i bought the motor

 

[steelespike]

Re: 1998 johnson 25

I don't think you have a cooling problem from your description earlier.
I would suspect some of the other components in the ignition system.Breaking down as they heat up.Someone may know how to trouble shoot.
If you had switched the coils you would have likely seen it still had the same problem. It would seem the ignition components associated with the top cylinder may be failing.A factory repair manual probably has the trouble shooting procedures.
If the mix was too lean lets say 100:1 you wouldn't notice till it started to rattle.
If it was too rich say 16:1 it would be smokey but would likely run the season without fouling.

 

[justen00]

Re: 1998 johnson 25

Just an update I ended up biting the bullet and buying a power pack cus I've been thinking that was the culprit, it ended up being that, I really appreaciate everyones help with this