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Problems with a rebuilt 1989 mercury 50hp.

J

Jkcckc2002

New member
I purchased this motor a while ago to repace the 35hp i had. This one had power trim and the older one didn't. Purchased it knowing it had low compression on all cylinders. Decarbed it and got compression up to 135 on all 3. Had a water leak in the #3 cylinder and i was going to replace the exhaust cover gaskets only. When i pulled tbe covers off the pistons were scored so i decided to rebuild it. Honed the cylenders, new pistons and rings bearings seals the whole 9.
So no i have everything back together and on the boat. It has new water pump, new fuel pump kit, and new cab kits in it. I have done the link and sync numerous times and cannot seem to get it to idle now enough. The timing and throttle pick up settings are giving me a hard time. Another thing is, I have One manual i have said the carb jets were in the wrong places, and another said they were correct.

If some one had some experience with thks engine or the mariner twin of it, i would apretiate the help.

Thanks

John
 
How many hours into breakin are we? Are the rings fully seated yet? Was the compression 135 before the rebuild? What is it now?
 
The bores were at stock diameter.2.875. I honed them to clean and deglaze them. Rechecked the bores and they were .001-.002 over. I went back with stock pistons and rings but new style two ring pistons.

The motor has less than one hour on it after the rebuild. I have been trying to get to where it would be able to idle in gear with out tearing up my gears. I know it has to have some resistance on it to break it in properly. But out of frustration i did check compresion on it yesterday to be sure something was not out of wach with it. The #1 piston had 115psi and the lower 2 (2&3) had 120psi.

I am trying not to go over 2000rpm while setting everything up but it just wont idle right for me.
I have no clue what was done to it by the guy i got it from but that thjng was so carboned up, thats what scored the pistons so much. It had 1/4 inch of carbon in the exhaust pasages and down pipe.
 
Are throttle plates completely closed at idle in neutral, Have you tried disconnecting throttle cable at engine from helm and adjusting
 
I can not get to run with the throttle plates closed. I have tried and tried. I have started at 1 turn out on the idle mixture screw all the way down to 1/2 out and back up to 3 turns out. They were completely taken apart. The only t parts the manual said to remove that i could not were the inlet elbows and the main pickup through the venturi. I did not want to ruin them because they are not available any more. Either way they got soaked over night in a b-12chem bucket and then blown out and sprayed with aresol cleaner and blown out again.

I have set the floats ans rechecked the floats. If some one can elaborate on setting the floats, it is strait forward but some times i over anilize things. With the carb upside down measure from the gasket mating surface to the top (bottom?) of the float, 11/16". If it is floating high that would richen the mixture and low lean the mixture. So i am in the trial and error stage.
 
Faztbullet, i didnt know that. Sure would have bumped it to a bigger piston and ring set.
I may have found the problem. I purchased it as a 1990, but it is a 1989. Serial # says 1990 but it is the older style block and components. The engine came with the buhw-2 spark plugs for the 1990. The plugs for the 1989 is the buhw, a .020 difference in gap. Do you believe this could be causing the idling issue.
 
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