1989/90 mercury 50hp questions

Jkcckc2002

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I have just rebuilt an 1989/90 mercury 50hp. It is a 3cyl 2 carb 2 stroke. The reason i say 1989/90 is that the serial # (0c281244) says it is a 1990. So i purchased a manual for it and it gives alot of info for a 1990 3cyl 50hp. But the illistrations do not depect my motor and upon further review the engine in the manual says it is a bigger bore than i have.
One of the problemss i am runnjng into is the link and sync and idle set up. I cant get it to idle low enough to even really begin set up.

So any sugestions on where to go from here.
 

racerone

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Sounds like you have the wrong manual.------Did you get a factory manual ?--------Does your manual show 3 carburetors and a loop charged motor ?
 

Jkcckc2002

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I dont know how to tell if it is loop charged or not. I have 2 seloc manuals now. One to 1989 and the first. From 1990. The older seloc has more info on it because it goes up to 1990. It is still pretty vauge on some of the settings. I have done the link and sync procedures but can not get it to run unless it is on fast idle with the butterflies open slightly. It cranks great and sounds like it is running great just wont run under 1k rpm.
 

racerone

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Your motor is NOT ;loop charged.----You need the correct manual in order to set this up.----What did you do to the motor to " rebuild " it ??
 

Jkcckc2002

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Well "l" didnt do anything to the engine to need to rebuild it. Its a long story, but ill condence it a little. I purchased about 2 months ago. I was told it had low compression, about 90 on all 3 cyl. Got that taken care of by de carbing the motor with seafoam soaks. Got the motor running good but the #3 blug was being steam cleaned. So i pulled the exhausr covers off to change the gaskets first(if that would not have fixed it then the lower seals). When i did, i did not like the way the lower half of the pistons looked. They were scored pretty bad. I couldnt just fix the water leak and call it good. So i decided to pull it apart and inspect it. I guess some carbon got behind the piston rings and scored the pistons. Tore it doen took some measurements, honed and measured again. Got some new piston, rings,seals,bearings etc. So now i am starting fron scratch.
 

racerone

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Have you looked at the water pump impeller ?------And you must clean the carburetors before trying to run this motor.
 

Jkcckc2002

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The first thing I did when I got it was order the water pump kit (housing and all) and 2 carb kits. that was done before I found the water leak in the #3 cylinder. When I got it they guy said it had 90PSI on all cylinders. I soaked it in strait seafoam for a few days then rolled it over to drain the carbon and seafoam out. did that 3 different times. Put it on a stand the started taking the carbs off and then the lower unit. Did the carbs and water pump and began to check compression. With 3 compression gauges at once all the cylinders were now at 135 psi. Then I proceeded to get it running. found a bad trigger and changed it out. I didn't take long to get it running, but I could not set idle with out it on my boat in the water to put in gear. while installing it on my boat I pulled the plugs only to find the lower cylinder plug clean as can be. it was wet with gas and oil and water, but almost brand new looking. so I ran it and checked temps with a non contact thermometer and it was indeed firing and getting just as hot as the other two. after some research on here and other places it came down to the exhaust plate gaskets or the bottom seals. the gaskets were the easiest to do so I was going there first till I saw the scoring on the pistons. After disassembly the cylinders were not bad at all, and the measurements were right at 2.875. once I honed it, it was barely 2.877-2.879 ". One thing I did notice while cleaning up the cylinders is that there was almost no chamfer on the intake and exhaust ports at all before honing they would almost cut you. that didn't seem right to me. so I cleaned them up before putting it together. now I am trying to link and sync and the manual I had first didn't seem to match what was there because it didn't . now I have another manual and there is still some stuff that doesn't match up. It appears it is a 1989 model that was supposedly a 1990 before they redesigned the block. I have that much strait now. one other thing I found weird is, in the carb jet size listing in the back of the manual, this 3cyl 50hp and the 3cyl 60hp of the same year models have the carb jets listed backwards from every other model in this manual and every other outboard I have worked on, although it hasn't been that many. they are saying that the main jet is a .086 and the bowl vent is .066. I don't think this is my problem with the idle but I am still new at this 2 stroke stuff.
 

Jkcckc2002

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Ok , got to thinking things through after that last post and i have pulled the jets out of the carb to verify what i have and where they are placed. Acording to the correct manual they were in the wrong place and are the wrong sizes. I had a .054(not correct for either model) in the main jet and a .092 jn the vent as per the 1990 and up manual . Now i have switched them. I know the .092 will be rich on the top end, but i will cross that when i get there.... now the .052 should be a .066 in the vent, nothing a 1/16 drill cant handle just to test. I may have been way too rich with the vent being that big.
 

Jkcckc2002

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Ok tried that for a little while last night on flushing atachment. Did seem to be better but i think i am still having a sync issue. I canot find what the timing at idle should be. The only wau it will stay running is at fast idle and then the timing is ocer 10* btdc and the carbs are starting to open. So what is your thoughts on this situation?
 

Jkcckc2002

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Dropped it in the water yesterday and i could not get it to idle. It would knly run if the fast idle was ingaged. On the carb linkage ramp/cam it will knly run on the primary pickup when the butterfies are beginning to open ans by that time the timing is around 10* btdc. It seems i have something adjusted wrong some where. Does anyone have one of these engines that could give some advice.
 

Jkcckc2002

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Ok going through some more things from one manual to another it seems i have the wrong plugs in the engine. The 1990 manual calls for buhw-2 and the 1989 calls for the buhw. Would this have an effect on the lack of idle? The surface gap is .020 wider on the -2 plugs.
 
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