1990 johnson 90hp quits when put into gear

[conchecko]

help! my 90hp johnson starts fine, when put into gear, it dies. it seems like as soon as it recieves a load....it quits. if one is lucky and you can get it into gear, and keep it going, it runs great during power-up, & wot. when just idling (hot or cold) in gear it will idle fine, but eventually dies out. it always re-starts, but not too easy, long cranking time. Boat has been out once last week during last 2 years. i have changed plugs.<br />Any thoughts anyone??

 

[DJ]

Re: 1990 johnson 90hp quits when put into gear

conchecko,<br /><br />A couple of things to look at.<br /><br />1. What is your idle RPM?<br /><br />2. What did the old plugs look like?<br /><br />3. Use CHAMPION plugs only. Gap at .30", .040" if you idle a lot.<br /><br />You may want to do this. See link.<br /><br /><br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=36;t=000016

 

[conchecko]

Re: 1990 johnson 90hp quits when put into gear

thx for replying so kwik!<br />i replaced all spark plugs, what i did see was (as viewed from rear of boat) top left plug electrode looked as thought it had been sprayed with aluminum??....after plug replacement and a hour of run time on lake...i pulled plug to recheck, it seemed ok, clean as other 3 where?<br />after typing this letter, i am off to do compression test. i will post results.

 

[conchecko]

Re: 1990 johnson 90hp quits when put into gear

idle rpm is around 900 when it does idle, and slowly dies off and stalls.

 

[G DANE]

Re: 1990 johnson 90hp quits when put into gear

The aluminium looking plug is probably covered with material melted from the piston top, I fear. Measure the compression to see if one has lost some. If it has, I would advise you to pull the head and see how much damage it has, and rebuild both carbs, as a lean running cylinder can reach temperatures where the alloy melts. Also check the sync'n linck adjustment.

 

[conchecko]

Re: 1990 johnson 90hp quits when put into gear

the compression shows 90psi across 3 of the 4 cylinders. The cylinder that had bad plug (aluminum on it) has 75 psi. a visual of piston tops through spark plug holes shows that problem cylinder looks a little different. I agree 100% with your overview in light of checks. Assuming Damage to piston in that cylinder isn,t catistrofic, can an engine perform with compression that isn't uniform across all cylinders??<br />thx again for input, very informative!!!!!

 

[G DANE]

Re: 1990 johnson 90hp quits when put into gear

If your gauge is accurate, your compression is on the edge. Maybe your motor has low compression headgaskets. I would start here by doing a decarb - look in FAQ's, after dissasemble and at least throughly cleaning the carbs. Compression should be within 10 % on all, at least in each bank, and best above 100. The three being 90 points at the gauge reeding low, or a need for decarb.

 

[conchecko]

Re: 1990 johnson 90hp quits when put into gear

i removed left head, the cylinder in question has a melted top. not severe......but i think a rebuild may be in the cards for me.<br />Thank-you all for your help/advice, it pointed me in right direction. Its not what i wanted to find, but its better than a tow off the lake!!<br /><br />tightlines!<br />Conchecko

 

[G DANE]

Re: 1990 johnson 90hp quits when put into gear

conchecko<br /><br />Is it possible for you to post a photo of the damaged piston top, maybe the damage isnt too bad, you might be able to raise compression with a decarb, clean your carbs and get a season or two out of it before the rebuild. If someone here can see the damage I an sure you will get good advise.

 

[conchecko]

Re: 1990 johnson 90hp quits when put into gear

I will take a photo of piston top and post next week. the portion of the piston that melted stuck on the top surface of it, i cleaned it, and lightly sanded piston top with emery. there was a noticeable oily/sticky residue on cylinder wall, (from sitting i suspect) so i sprayed with solvent and cleaned well. At this point i think its worth re-installing cylinder head (w/new gasket), and move on to cleaning carbs. As i say, other than dieing out when put into gear, motor works well. I am hoping this is just a case of motor sitting for a long period of time and in need of a good cleaning despite piston problem.<br />Thank-you again G Dane, for your efforts to help me out, it truly is appreciated!!!!<br />HAVE A GREAT WEEKEND!<br />Conchecko

 

[G DANE]

Re: 1990 johnson 90hp quits when put into gear

If your motor ran well at iddle in gear, and mid- and wot-range, the "dieing when put in gear" issue may very well be from dirty carbs, and/or misaligned sync'n linck adjustment. Do you have a manual to help you thru this procedure and carb syncronisation when you have disassembled, soaked,cleaned and assembled carbs ?. A little oil on cylinderwalls is only good. If its sticky and mixed with carbon, a decarb will do it good. Rember to warm it up first.

 

[conchecko]

Re: 1990 johnson 90hp quits when put into gear

I don't yet have a manual, but will purchase before i remove and clean carbs. What is the name of this product you spray in engine to "decarb"?<br /><br />Thx<br />Conchecko

 

[G DANE]

Re: 1990 johnson 90hp quits when put into gear

OMC call it "Engine tuner" Yamaha "Ring free"

 

[G DANE]

Re: 1990 johnson 90hp quits when put into gear

You can also use the Sea Foam products. Do a search on carb cleaning or soaking here, plenty af good advise.

 

[ralphjg]

Re: 1990 johnson 90hp quits when put into gear

i bought sea foam and Deep Creep (aerosol spray) at Auto Zone

 

[conchecko]

Re: 1990 johnson 90hp quits when put into gear

Thx G Dane, & ralphjg........i will try one of these out...........once i get my manual, i would like to disconnect vro and mix fuel myself. Is this a bad thing todo? Do i have to retro-fit fuel pump to eliminate vro?? I just bought boat, i am learning more & more each day. i think with a "decarb", And rebuilding/cleaning carbs will overcome my "dieing when put into gear", but i especially want to make sure that if things work out, that engine is getting oil it req's.

 

[G DANE]

Re: 1990 johnson 90hp quits when put into gear

If the wro is the original one, its been working for 14 years, I would recommend to replace it. You can disconnect the oil side and premix if you want, just do a search for disconnection vro on this site and you will know exactly how, requires no parts. You can easily check if it works as it is supposed, too if you want that, just do a search, premix oil/gas, mark a line on oil tank and observe oil consumption, compared to gas usage. The failure you just had is definately not VRO failure, the unit mixes gas to all cylinders at one time. When these motors gets older, they tend to like the extra oli it will get when you premix, though.

 

[conchecko]

Re: 1990 johnson 90hp quits when put into gear

Thx for info.......i have learned alot from advice/expertese that you & others have offered.<br /><br />thank-you again,<br />Conchecko<br />ps. i intend to re-asemble head, and rebuild carbs, before season is done, I will be sure to post on this thread my results, if motor works.<br /> thx again

 

[G DANE]

Re: 1990 johnson 90hp quits when put into gear

BTW the procedure is, wheneever an oil hose has been off,tank cleaning has been done, or any service done at all, at any part of the oil system. Run motor on 1:50 premix untill proper oil usage is verified. The overoiling during this period wont hurt anything.

 

[conchecko]

Re: 1990 johnson 90hp quits when put into gear

What is torque on cylinder head for this motor? aswell, the cover that fastens to top if head that seals water jacket? When tightening head down, head bolts get tightened from center out, right?<br />I am gonna re-assemble 2morow, i called local supplier for "seafoam", they (carquest) can't say enough about it, it comes in a spray form called deep creep......i will study well and apply....<br />thx G Dane,<br />Conchecko