1999 Johnson 25hp 3 Cylinder,,Need Input

[Murp]

,I have a 1999 Johnson 25 hp 3 Cylinder,,I bought this used late last season on a Carolina skiff,before I put the boat in,I put complete Brand new water pump in,old one was shot,also seen the thermostat assembly was mising,put a new Thermostat and assembly unit in,check compression in all 3 cylinder warm up was 105psi ran motor for a good hour every thing look and sound good motor started on the first turn,,put it in the water ran for about 15 min easy just got over half throttle and bang sound happen,started missing running rough at this point if I went over ? throttle it would shout off,then hard to start, Idle back to the dock,a guy at the marina said the motor was shot,,that he could have it rebuild,ouch, hi Dollar,,,I know car engines have rebuild a fue,just don?t know these 2 strokes,today I just put it on the hose and ran it for a hour sound good started first turn,check compression still 105 in all 3 cylinder no hesitation with the throttle,,would appreciate any HELP,,is there something I?m missing,or need to check,,,,I just never seen a motor with good even compression and spark and fuel and start on the first turn, Be Bad Thank You

 

[Haffiman]

Re: 1999 Johnson 25hp 3 Cylinder,,Need Input

Gear case break down??
Check oil for contamination.

 

[Murp]

Re: 1999 Johnson 25hp 3 Cylinder,,Need Input

Haffiman,,I Check and replace Gear Case oil no signs of contamination,shift motor into forward and reveres shift very smooth and no sounds of any straining on the motor,,Guys I really appreciate any Help with this motor

 

[boobie]

Re: 1999 Johnson 25hp 3 Cylinder,,Need Input

Have you taken it and tried it on the water again ? Have you removed the oil tank and are using 50:1 premix? If you're not using premix, stick your nose in the oil tank and see if it smells like gas/fuel.

 

[nwcove]

Re: 1999 Johnson 25hp 3 Cylinder,,Need Input

had the same motor, bought new, 30 mins into its maiden run......it backfired and stalled, restarted it and it was like it was running in slow mode. the powerpack was the issue. if your "bang" was mechanical rather than a backfire, its probably not the same issue, but if it was a backfire, it could be worth looking into.

 

[Murp]

Re: 1999 Johnson 25hp 3 Cylinder,,Need Input

Boobie,I did not try it in the water yet,just on the hoes,the VRO pump is still connected, I’ve been thinking of disconnecting the VRO pump,this is something I did trying to check that the pump was working or putting oil to the motor,I removed the float bowl screws from each of the carb’s,,with fresh gas in the tank I started to pump the gas thru the system and out the float bowl the gas coming out the bowl was Blue like the oil in the VRO tank,,Im not at the boat right now to smell the oil in the tank,,,I did see their only one line goes from vro tank to vro pump,,,just queries on smelling the oil in the tank,,

 

[boobie]

Re: 1999 Johnson 25hp 3 Cylinder,,Need Input

These mts had a prob with the oil mixing valve screwing up and pumping fuel into the oil tank and leaning out the oil mixture so bad it would lock up the mtr. The best thing you could do is get rid of the oil tank and mixing unit, do a little fuel line plumbing and run 50:1 premix. As long as you still got good compression your mtr might be okay, but leaving that oiling system on it, who knows???

 

[Murp]

Re: 1999 Johnson 25hp 3 Cylinder,,Need Input

nwcove,and boobie,your Info in your post has me really thinking on the actual sound I heard that day,,after reading your post it was more like a hard backfire with compression,,like the motor tried to lockup,or a cylinder loaded up,sat for 15min started ran little rough but would not run over ? throttle,,,,,boobie when I get back to the Boat that will be the first thing I do Disconnect the vro hopefully with that compression being even 105 thru all 3 cylinders I’ll be ok,,,,,,nwcove,you say the powerpack was your issue
Backfired and stalled after you restarted, it ran in slow mode,in that mode at slower speeds was there any signs of it running rough,,is their a way of checking the Power pack or you need to replace and see ,,the hard backfire happen one time,,Guys I can’t thank you enough for taking the time to helping me out,,,,l’ll be making a check list,,,any more suggestion would be appreciated

 

[nwcove]

Re: 1999 Johnson 25hp 3 Cylinder,,Need Input

mine did the backfire 15 mins into its run ( motor was brand new), it stalled, was hard to start. got it going and limped back to shore...it did run rough/shake. i checked it over and it was only running on two cyls, so the dealer gave me a coil to fix the issue which made no difference, he ended up checking the powerpack and it had failed. im not sure of the exact method to check your powerpack, hopefully someone will chime in and steer you in the right direction if you wish to check it or have it checked.

 

[Haffiman]

Re: 1999 Johnson 25hp 3 Cylinder,,Need Input

That powerpack may only be 'checked' by replacing it. You may however measure primary to coil and even charge coil.

 

[wmmills]

Re: 1999 Johnson 25hp 3 Cylinder,,Need Input

I have a power pack problem one of the coil leads are not working could it be the power pack or could it be the stator not firing the power pack ?

That powerpack may only be 'checked' by replacing it. You may however measure primary to coil and even charge coil.