dissapointed after powerhead rebuild, help needed

greasemonkeyjmj

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Some may remember i bought a 1987 Evinrude 48SPL that wouldnt idle consistently, i tore the carbs down and they were spotless, but i soaked them anyway, later on I discovered both pistons were ruined and the block was scored, i just got it back from being bored and new pistons, I put everything together, and it will not idle, i have the idle screw all the way in and it still doesnt want to run, the carbs are the fixed jet type that has no air adjustment. any help would be greatly appreciated as I am at my witts end.


Thanks
 

boobie

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Even though its just been rebuilt, what's the compression on it ??
 

greasemonkeyjmj

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150 on both cylinders, i pulled the top carb and drilled the plug out of it, and there are only 2 holes into the throat for the idle circuit and they are both clear. i can also shine a light into the plug hole and see it shine all the way through the fixed air jet.
 

Faztbullet

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Mar 2, 2008
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Its a loopers and pistons can be installed upside down, it will have compression but the piston cutouts wont line up with ports in block and it will run but crappy...
 

Chinewalker

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Have you done a link and synch according to the manual?
Is the thermostat present and working?!
 

greasemonkeyjmj

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Metric, i have no idea, when i bought it, it idled rough on the hose, and would hardly idle as all if lucky in the water, when i tore into it, they were running 100:1 mix, and the pressure valve on the ccoling system was melted, so something had gotten warm.it is on a 24 foot pontoon running a 13 3/4/ x 15 prop with no tach, so there could have been a mixture of problems that led to it. but I may have found a problem. i had it running and took a can of spray carb cleaner and shot a blast under the flywheel, and it idled up and smoothed out, so apparently there is a problem with the crank seal, i put new seals in it, but apparently something isnt right.
 

torbjorn

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100:1 is very wrong. Never less than 50:1, and with good oil. Evinrude, Mercury, Yamaha, Amsoil. Run 100:1 and you'll score pistons regularly. You need a tach to see that the motor's turning 5500-6000 RPM wide open. Otherwise you aren't developing the expected hp.
 

greasemonkeyjmj

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yeah im not wanting to put it in the water until i get a tach added to it, and i am sure that i am going to have to go down on the prop to get it spinning faster, this is if i can get it to run correctly
 

greasemonkeyjmj

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What symptoms will leaking reeds cause on my engine i remember when i tore the engine down that on one block, that out of the 8 fingers, almost everyone of them was letting at least some light thru where they werent sealing off
 

racerone

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Dec 28, 2013
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I doubt there is a problem with the top seal.-The spinning flywheel would direct that spray towards the carburetor intake.-Re-examine your carburetors.-----Did you remove the high speed jets found in the carburetor bowl ?--They are screwed in horizontally.
 

racerone

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Air pressure will close those reeds.-It does not take much of a gap to show light through them.
 

greasemonkeyjmj

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Actually there was a problem on the upper crank seal, when i installed the seal, i only drove it down flush with the top edge of the roller bearing assembly, and it wasnt actually sealing off around the crank, i drove it on down and put it back together, it is still not running smooth, i was really thinking that was my problem. i am second guessing myself on the direction that the seal goes in although i put it the same direction as the old one, it is my thinking that part of the seal that bevels in should face upward, so that the suction of the crankcase would be pulling the seal against the crank, because if you put it with the beveled part down, the suction would be able to let air suck it open and get by. I also had a person tell me that running my fuel mix at 25:1 for breakin will cause a rough idle, what your thoughts on that ?
 

racerone

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The seal should be installed with that spring towards the crankcase.------Perhaps you are starting to " overthink " some of the simple things on your motor !---Do not listen to " someone " as many folks just do not know how these motors operate.
 

greasemonkeyjmj

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this is the direction that the seal was installed and the direction i installed the new one, with the spring facing upward towards the flywheel. and yes I am starting to overthink things on this engine. Iam at a loss as to what the problem could be. I even did the paper test on the reeds and had a little spray back out of the carbs, so i pulled the reeds, with the exception of one aving a tiny gap, the rest looked fine.
 

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