1990 90h hp evinrude carb jets

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shrinkinfoot

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need more help!! when talking to a local boat shop about the top 2 plugs fouling and poor high speed performance with a severe power loss above 4000 rpm and it was recommended to replace the carb jets going from 56c to 26c....(it is the only boat shop within 100 miles) or should i replace them with 56c ( they would have to order them 3 weeks??) the book says 56c but he says the 26 will be fine??
any suggestions...................THANKS:confused:
 
Faztbullet

Faztbullet

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Re: 1990 90h hp evinrude carb jets

56C is the high speed jet, 26 is a low speed, this may help plug fouling at idle but nothing for 4000 rpm and above performance. You have more issues than jetting...I going to lean toward a electrical problem(rectifier or pack)
 
tashasdaddy

tashasdaddy

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Re: 1990 90h hp evinrude carb jets

welcome to iboats. is this a Johnson/Evinrude Certified shop. does not sound like it. 1st where are you, sea level, high altitude. the motors are designed to operate with the original jets to about 4-5,000 feet elevation.

you can order the jets your self right here. http://shop2.evinrude.com/ext/index.aspx?s1=bf6ad09c53cead335fcfd8a6471c0f7f

i would suggest doing a decarb on the engine, and get the excess carbon out of it, simple procedure. http://forums.iboats.com/showthread.php?t=302825
 
psteurer

psteurer

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Re: 1990 90h hp evinrude carb jets

This solution is likely a band aid for a different problem. You may want to consider a compression check to ensure all cylinders are within 10%. Have you had the carbs rebuilt? Dirty carbs could also cause the problem you are experiencing.
 
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shrinkinfoot

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Re: 1990 90h hp evinrude carb jets

carbs are being rebuilt ...) no authorized dealers here ( this is when they said use 26c for replacement jets???... at sea level (boat is in belize) and only the top two plugs foul the bottom two burn clean... new fuel and 50/1 premix used have not put in water yet..... only authorized yamaha dealer close in mexico.. should i go to them for help?? boat sat for two years replaced the fuel lines,bulb, removed and cleaned tank, tried different brand plugs, champion seemed better...( have not de-carboned anything, compression good on all cyls...
 
tashasdaddy

tashasdaddy

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Re: 1990 90h hp evinrude carb jets

compression is good. what is good??? the motor was built to run Champion QL77JC4 spark plugs, gapped at .030. if you are using surface gapped plugs, they are known for fouling.
 
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shrinkinfoot

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Re: 1990 90h hp evinrude carb jets

compression at high 115 to 105 low used the champ no gap .... then went to ql77jc4 plugs.... cylinders and top of pistons look carbonized ( from sitting??and running rich??) i only use this as a pleasure boat (pontoon party hut) lower speeds only
 
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shrinkinfoot

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Re: 1990 90h hp evinrude carb jets

the motor also had a bad gas smell when removed engine cover but didnt see any leakage....
 
tashasdaddy

tashasdaddy

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Re: 1990 90h hp evinrude carb jets

get rid of the gas, new alcohol resistant fuel lines, carbs to tank. clean the carbs, decarbonize, then new QL77JC4 plugs, gapped at 030. i have owned and serviced many of these particular motors. the worst thing is for a motor to just sit. start it atleast once or twice a month. open it to Wot for 5 minutes every use.
 
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emdsapmgr

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Re: 1990 90h hp evinrude carb jets

Sound like something is different inside the upper carb vs the lower carb. Someone may have been inside the upper carb. I'd pull the upper apart and check the jets vs the factory parts list spec., then clean/overhaul it to like new. Check for cracks in the body and make sure all the round aluminum discs (covering the machining holes) are in place and still sealed. Esp, replace the float and needle and seat during overhaul. Remove all jets and clean all passages and jets with an aerosol carb cleaner. You need at least one carb kit: 439076.
 
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