Johnson 90 HP Binding?

[jeepers94]

I just bought a 1990, 90 HP Johnson VRO as is from an auction. Compression was 115-120 all four cylinders. First time out it turned over very heavy but started after a few attempts. Ran well one trip out but there was a knocking sound such as with poor gas in a car. VRO bypassed mxed oil in tank. Second time out turned over heavy but would not start. Eventually starter gave out, literaly. Starter replaced and still would not start. Mechanic is leaning toward sever engine damage, possibly bad rings that is binding the engine? Without the spark plugs it turns over easily. I cut my losses and brought it home and opened it up myself. Cylinder walls look ok, no scoring. One postion looks like it has been "burned". Beyond that I don't know what I need to look for. I did notice pistons have some play within the cylinders. Normal? Any help would be appreciated.

 

[almost retired again]

Re: Johnson 90 HP Binding?

Hi jeepers ,<br />The binding could be caused by the lower unit,or gearcase. You could drop the lower unit, then see how it turns over. Pull the drain plug at the bottom of the gearcase see what the oil looks like, and how many metal particals are attached to the little magnet thats on the drain plug. This will give you a good indication of the condition of the gears inside.<br />Good Luck

 

[jeepers94]

Re: Johnson 90 HP Binding?

ARA, <br /><br />I pulled the plug and there were very few shavings. I understand that is probably normal? The oil was dark like it need to be changed out. As soon as I pick up a repair manual, I will consider dropping the lower unit. Anything else I could look at in the mean time?<br /><br />Thanks for your help.

 

[superman]

Re: Johnson 90 HP Binding?

With the spark plugs out how hard is it to turn by hand and are there any unusual noises. It should turn easy except for crankcase back compression.

 

[DJ]

Re: Johnson 90 HP Binding?

Superman,<br /><br />Your water pump, impeller, could be binding.

 

[jee70611]

Re: Johnson 90 HP Binding?

It could possibly be out of time a little. It could be firing too soon making it harder to turn over. Just a thought. Good Luck

 

[jeepers94]

Re: Johnson 90 HP Binding?

Thanks for the input so far. <br /><br />As far as impeller, it is new and the problem existed prior to changing it out. <br /><br />With the spark plugs out, it turns easily enough and I don't hear anything out of the ordinary. There was the knocking during operation when I used it last but I don't hear anything when I turn it manually. <br /><br />Should the piston be able to "rock" within the cylinder or should it be a tight fit against the cylinder wall? All four pistons have some play. I can push up or down of them and I can rock them within the cylinder. <br /><br />How do I check/adjust timing?<br /><br />Thanks again

 

[jeepers94]

Re: Johnson 90 HP Binding?

I got my hands on a Clymer manual and tinkered around with the engine a bit more. In another post, I had read that timing does not change unless it was adjusted at some point and was not correctly reset. When I read that I thought I was back to square one but after reading the timing setting on the manual I went back to the engine and found someone had used a crayon to mark the correct timing on the flywheel. That leads me to believe that it was adjusted and that it might be incorrectly set. I don't have a timing light so can I hit and miss the adjustment by turning the appropriate wheel as indicated in the manual?

 

[Joe Reeves]

Re: Johnson 90 HP Binding?

Jeepers..... You can check and adjust the timing as follows:<br /><br />(Timing At Cranking Speed 4°)<br /><br />The full spark advance can be adjusted without have the engine running at near full throttle as follows. <br /><br />To set the timing on that engine, have the s/plugs out, and have the throttle at full, set that timer base under the flywheel tight against the rubber stop on the end of the full spark timer advance stop screw (wire it against that stop if necessary). <br /><br />Rig a spark tester and have the spark gap set to 7/16". Hook up the timing light to the #1 plug wire. Crank the engine over and set the spark advance to 4° less than what the engine calls for. <br /><br />I don't know full spark advance setting your engine calls for, but to pick a figure, say your engine calls for 28°, set the timing at 24°. The reasoning for the 4° difference is that when the engine is actually running, due to the nature of the solid state ignition componets, the engine gains the extra 4°. <br /><br />If you set the engine to its true setting at cranking speed, when running it will advance beyond its limit by 4° which will set up pre-ignition causing guaranteed piston damage! You don't want that to take place. <br /><br />No need to be concerned about the idle timing as that will take care of itself. The main concern is the full advance setting. <br /><br />Be sure to use your own engines spark advance settings, not the one I picked out of the air here in my notes.

 

[jeepers94]

Re: Johnson 90 HP Binding?

I am getting somewhere. I dropped the lower unit and low and behold the noise that it was making stopped. I have yet to test if it will turn over easier by cranking the engine but it does turn over easier with and without the sparks plugs out and the noise has stopped. The only sound now is the woosh of the compression. I think that is a good thing, right? Anyway now I need some help with the next step. If indeed it is the lower unit causing the heavy starting now what. New lower unit? It was running so is it worth rebuilding? Can I tear that open up myself or is this better left for a professional? Is this a major expense or can it be repaired on a budget?

 

[slow_boat]

Re: Johnson 90 HP Binding?

Just a thought but, are you sure you put the impeller in so the the vanes are turning in the proper direction? It can be easy to orient them the wrong way when changing the impeller, thus causing pretty significant binding.

 

[jeepers94]

Re: Johnson 90 HP Binding?

Slow_Boat, <br /><br />Thanks for the input but the problem existed before the new impellar. I just did not know how serious it was/is or otherwise I might have thought twice about spending that money. I had the impellar changed out by a shade tree marine mechanic so I am hoping he did it right but since the problem existed before I would lean away from that being the problem. Although, it could not hurt to look since I have the unit down. How can I tell how it is supposed to be installed?

 

[Hooty]

Re: Johnson 90 HP Binding?

If they're installed wrong, new impellers are usually flexible enough to "fix" themselves after the first coupla revs.<br /><br />c/6<br /><br />Hooty

 

[ob]

Re: Johnson 90 HP Binding?

Look at flywheel and determine direction of rotation.Follow driveshaft down to where it drives impeller.Flutes should bend away from direction of rotation.I concur with Hooty.These impellers will generally turn themselves around if flutes are bent the wrong way.Just don't install key backwards.