1989 90 HP Evinrude rebuild

[vranasaurus]

The motor is a 1989 90 HP Evinrude. <br /><br />I bought the motor took it out and got no power and the overheat alarm was going off. I did a compression test and all cylinders read 120-130 except for the top right which read 0. I pulled the head and there was extensive damage to the one cylinder. There were deposits on spark plugs. As well as on the top of the piston. I currently have the motor apart with the block at the machine shop. But I would like to know what could cause this one cylinder to fail like that. I think it might be a detonation problem but I am not sure. I don't want to put the motor back together without correcting the original problem. <br /><br />Any help would be greatly appreciated.

 

[Dhadley]

Re: 1989 90 HP Evinrude rebuild

Welcome and good thinking!!<br /><br />Youd be surprised how many motors get put back together without correcting the cause of the failure.<br /><br />We'll need to know a bit more before we can steer you in the right direction. We need to know exactly what the piston looks like. Are the sharp edges worn away? Sides scuffed but top OK?<br /><br />Had the motor been sitting without being run just before this? Was the timing set/checked? If so, what proceedure?<br /><br />What spark plugs? Fresh fuel? (6 week old fuel is not fresh)

 

[vranasaurus]

Re: 1989 90 HP Evinrude rebuild

The plugs were brand new. Fuel bought same day as I went to the lake. I don't know how long the motor sat before I got it. <br /><br />The piston looked as if molten metal had landed on the piston and cooled.<br /><br />Material from the cylinder wall had covered the rings on one side. Maybe when I get home I can take some pictures so you can see. <br /><br />I didn't check the timing. I thought about a timing problem but how do you time the engine without going WOT during the break in period?<br /><br />I will try and get pics

 

[Dhadley]

Re: 1989 90 HP Evinrude rebuild

What spark plugs were in it?<br /><br />Since we dont know how long the motor sat the carbs are always suspect. At some point of the rebuild make sure they get a good bath and new OE kits.<br /><br />There is a way to preset the timing and it will be very close to correct. Joe Reeves has an excellent description. But that brings up something.<br /><br />You mentioned the break in period. Are you saying that the motor was just rebuilt? If so the rebuilder/installer should have set the timing. <br /><br />From your description we imagine that the edges of the piston are all burned away. Correct?

 

[vranasaurus]

Re: 1989 90 HP Evinrude rebuild

I am currently rebuilding it. <br /><br />The plugs are champion plugs. I don't have the exact part number.<br /><br />Carbs looked pretty good, no varnish/stains or otherwise, but was planning a rebuild anyway.<br /><br />The sides of the Piston has have vertical marks, and the top has a lot of deposit on it.

 

[vranasaurus]

Re: 1989 90 HP Evinrude rebuild

here are some pics<br /><br /><img src="http://i4.photobucket.com/albums/y101/vranasaurus/72900d75.jpg" alt="Image hosted by Photobucket.com"><br /><br /><br /><img src="http://i4.photobucket.com/albums/y101/vranasaurus/3f17836f.jpg" alt="Image hosted by Photobucket.com"><br /><br /><br />The spark plug is a champion L77JC4

 

[vranasaurus]

Re: 1989 90 HP Evinrude rebuild

I looked at all the plugs:<br /><br />Bottom two cylinders were both black and fouled in appearance.<br /><br />Top left cylinder was completely clean and shiny<br /><br />top right had deposits on it.<br /><br />Maybe there's something you can glean from that

 

[G DANE]

Re: 1989 90 HP Evinrude rebuild

I think you are dealing with a couple of different issues. <br />Both of the top cylinders being clean and dry tells us that carb must be fouled, having a bad fuel feed, as the two cylinders was running lean, suffering from high comdustion temp and bad lubrication. You can see the carbon on piston top is burned and melted to a grey layer. If you look at the side of piston its clear that half of the upper piston ring hasnt been in contact with cylinder wall for a long time. This is caused be carbon deposits, locking ring in groove, probably because motor has too high propeller pitch, causing carbon build up, by logging at too low rpms. And not being regulary cdecarbed. <br /><br />But other know lots more than I, better wait for them.

 

[vranasaurus]

Re: 1989 90 HP Evinrude rebuild

^

 

[G DANE]

Re: 1989 90 HP Evinrude rebuild

bump

 

[vranasaurus]

Re: 1989 90 HP Evinrude rebuild

bump

 

[Basscat 1]

Re: 1989 90 HP Evinrude rebuild

I see the problem in the bottom picture. Isn't that a Bud-light? Most outboards run better on Coors-light.... <br />Just kidding.

 

[Dhadley]

Re: 1989 90 HP Evinrude rebuild

You mentioned the break in period. Are you saying that the motor was just rebuilt? If so the rebuilder/installer should have set the timing.

Was the motor rebuilt just before you bought it?<br /><br />Just looks like the cylinder leaned out. Most likely from a carb problem.

 

[vranasaurus]

Re: 1989 90 HP Evinrude rebuild

I bought the motor from some guy in Louisianna. I put it on my boat and it took a crap. I am rebuilding it. This things has begun to dominate my thoughts like only an outboard motor can. <br /><br />I am going to put it back together and try Joe Reeves timing method that I got from another thread. I think it was a timing issue. I do know that the #1(bad cylinder) and #3(starboard side) cylinders were rebored while the #2 and #4 were not. I am going to soak and rebuild the carbs.<br /><br />The Carbs however show no outward signs of malfunction.<br /><br />It may be a combination of carb plus timing.<br /><br />Would a lean condition cause these kind of deposits on the piston?<br /><br />BTW, that is a coors light, but I am sure my outboard would run better on something a little higher proof.