1990 90 HP Evinrude. Couple of questions.

[cs90453]

I have a 1990 90 HP Evinrude that is not running properly. Carbs have been checked and cleaned. Engine seems to be good at high speeds. Runs really rough or shutting off at low speeds. Any ideas?

 

[marinemech]

Re: 1990 90 HP Evinrude. Couple of questions.

top gaskets on carbs may be swelling up plugging idle passage<br />engine temp too low<br />engine sync out<br />compression low <br />poor quality fuel/oil<br /><br /> check comp first then carb gasket top one is easy to remove proper gasket should be cut out for idle passage then check temp both heads should be warm to hot on top then try re-sync procedure

 

[cs90453]

Re: 1990 90 HP Evinrude. Couple of questions.

Thanks. I will check the gaskets. I will then check the timing. Compression was between 90-95 lbs. Could it be powerpack?

 

[cs90453]

Re: 1990 90 HP Evinrude. Couple of questions.

I forgot to ask. What would be normal compression for a 90 HP?

 

[Bradster941]

Re: 1990 90 HP Evinrude. Couple of questions.

That's a little lower than I like to see, but as long as it's even, 5 to 10psi per cylinder, it's O.K.. <br />Your problem lies else where.<br /><br />Marinemech is right. Spend a few bucks for a carb rebuild kit. Chances are it hasn't been done in a long time anyways.<br /><br />Check the temp on the heads. Should be 135 to 145 degrees after warm up. If lower then that, it can cause rough idle. Replace stats.<br /><br />The manual will give you specs. on checking the timeing. <br /><br />Post back and let us know how you make out.

 

[DJ]

Re: 1990 90 HP Evinrude. Couple of questions.

Do this, while you're at it.<br /><br /><br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=36;t=000016

 

[cs90453]

Re: 1990 90 HP Evinrude. Couple of questions.

Thanks for the advice. I will check everything out and send back an update. I have found out that I have NGK plugs in the engine and I should have Champions for that engine. I've heard that NGK's will make the engine run bad. Ever heard of that?

 

[marinemech]

Re: 1990 90 HP Evinrude. Couple of questions.

ngk plugs will make omc outboards do really strange things only use champion plugs and be sure they are proper number

 

[cs90453]

Re: 1990 90 HP Evinrude. Couple of questions.

I had a chance to look at the engine over the weekend. I changed the plugs to Champion and installed new wires. Engine fired but one of the cylinders are going in and out at low speed. Once I get the engine over 1500 rpms the engine is smoother. I think that the plugs made the difference. Going to clean the carbs and resync. Compression is in the high 90's but all are the same. The engine wasn't running for over 18 mnths so I'd say that should be more after I run it for a couple of tanks.

 

[G DANE]

Re: 1990 90 HP Evinrude. Couple of questions.

Take my advise and DONT RUN it untill you fixed the problem. Clean the carbs, including soaking overnight and blow thru all passages. Install rebuild kits. If you run it with a cylinder not firing, the unburned fuel/oil will wash all oil from the bad cylinder and you risk severe scoring.