1982 Evinrude 90

[mwc32m]

Bought a boat from an estate knowing that the motor (e90tlcnb) would be a project and purely a bonus if it worked. I want to determine if it is repairable, but I don't want to put a lot of money in until I know it will work. The wiring harness from the helm to the motor is disconnected. The motor is essentially stand-alone. I put a battery to the starter and it spun, but not fast enough. The brushes were worn, so I installed a new starter. It spins faster now, but no spark in any cylinderand only about 30 psi in each cylinder. Through my search online it sounds like I need to disconnect the killswitch wire (black and yellow?) in order to get spark. I am wondering what would account for the lack of compression and if there is anything else I need to do before I can get a true compression reading. There is no key for the ignition switch but that shouldn't matter if the wiring harness isn't connected to the motor, right?

Thanks

 

[Sixmark]

Re: 1982 Evinrude 90

Well considering that you don't need spark for a compression reading and the fact that you only have 30psi in each cylinder, I would find out why the compression is that low before I would even mess around with getting spark to it. Pull the head off and look for damage to pistons, cylinder walls, etc.

If you are lucky then maybe it's just a head gasket, then you could replace it and move on to the ignition. If there is major damage to cylinders and pistons then you might be in for a large project.

 

[emdsapmgr]

Re: 1982 Evinrude 90

Sixmark is on target. That engine won't run with only 30 lbs compression. I would think the compression would normally be in the 110+ lbs range. You said you were missing the control box and harness. You should not have to worry about the black/yellow wire in that case. You have to spin it between 200 and 250 rpm to get the ignition system to fire. If you crank that engine by jumping the starter, the ignition system normally will work by itself and you should get the engine to start-at least fire. The only thing you can't do with the control box harness disconnected is to turn the engine off once it is running. If the prior owner overheated the engine-then sold it, the head gaskets could be trashed-check them first.

 

[metriccrescentwrench]

Re: 1982 Evinrude 90

I've got a 1981 90 HP, essentially the same as yours, it's been a great running and reliable engine. Emdsapmgr's right on the money with compression. If you do get everything right it'll be a good engine for you. Oh, I read somewhere (wish I could remember where) that OMC changed the spark plug recomendation to Champion QL82C, so that's what I started using and in fact they seem to work much better.

 

[mwc32m]

Re: 1982 Evinrude 90

Things have gotten much worse. I am admittedly not very good with engines and enlisted more help today. The compression was low because the motor was not spinning fast enough. Replaced the solenoid. Motor spins much faster now and got higher compression (also got spark on all 4 cylinders). 100psi each on 1 side. However on the other side one cylinder was about 75 and the other was not registering. Removed the head to find scoring on both cylinders and a significant wobble in the pistons. The cylinder that showed 75psi actually had more scoring than the one with no pressure. My question here is what do I do next? I've read that I can bore out the cylinders but that the cost to do so is almost as much as buying another used motor. Can I buy a new block? Or am I better off to just find a used motor?

 

[emdsapmgr]

Re: 1982 Evinrude 90

Those pistons in that engine do have quite a bit of clearance. That's normal. The question is what do the seal rings on the head gasket look like on the low compression head? If the seal rings are broken, you can just replace the head gasket. If the seal rings are intact, that's a sign the rings may be damaged. Are there any dents in the top of the piston and head? It is permissible to bore only one or two cylinders on that engine. If you choose to reuse the two existing (good) pistons, you should get two other factory .030 oversize to match them. You will need 4 new ringsets on any overhaul.

 

[archcycle]

Re: 1982 Evinrude 90

FWIW, I wouldn't take the risk of a major overhaul on that if I were you. There are so many more problems that could come up after you get the compression problem fixed. Ignition, fuel delivery, lower unit problems.. For the price of what you're about to do you ought to be able to find a running motor that shares most or all parts and just keep that one on hand for spares and troubleshooting parts.