1986 50 horse rebuilding troubles

[rolmops]

I completely rebuilt a 1986 50 horse evinrude.I replaced the pistons had the cylinders done 20 oversize,replaced the seals and so on.So it is completely rebuild now.Also the VRO was replaced with a regular fuel pump.It still sneezes a bit while running on the muffs and I suspect the fuel supply manifold hoses to be too small.<br />When I tried to determine what cylinder was running lean and sneezing I put my hand over the carburetor mouths and found out that while trying the upper carburetor it hardly lowered the rpm but gave a lot of fuel in the barrel,while when covering the lower carburetor it would shut the engine down.Same thing with pulling the plug wires.When pulling the top wire off the plug It would make a little difference but not much.When pulling the wire of the lower plug it would shut the engine off.Am I looking at a reed job or is this possibly something electronic?<br />As always your help,advice and opinions are highly appreciated.<br />Rolmops.

 

[david18]

Re: 1986 50 horse rebuilding troubles

If the reeds were bad it would have been apparent when you tore the engine down. These are good motors but have very sensitive carbs. Every jet and orifice must be clean. Take your carbs apart and blow carb spray and high pressure air thru everything...twice.

 

[rolmops]

Re: 1986 50 horse rebuilding troubles

A little light lit up in the head of this shade tree mechanic.If the upper carb does not start sucking air real hard when I cover the barrel completely.It would mean that it is getting air from elsewhere.Am I on the right track here?Could it have to do with the upper carb low speed airbleeder being a bit loose. (housing turns loose in the shaft)and if that could be the problem,how do I solve it? Short of replacing the entire carb? <br />Please help,I am a political scientist not an outboard mechanic. Every time I work on another outboard ,it is a journey of discovery with lots of trial and even more error.I feel like a detective,except,I do not know what there is to discover.

 

[rodbolt]

Re: 1986 50 horse rebuilding troubles

do your carbs have fixed jets for idle or air fuel mix screws?<br /> without looking at it I caant remember. do your carbs have a black plasitic top with an air jet on the fwd stbd corner ?

 

[rolmops]

Re: 1986 50 horse rebuilding troubles

Hello Rodbolt.<br />The carburetors have what is called an "idle air bleed orifice" in the top.It does not have a black plastic top and there is nothing adjustable on the forward starboard corner.<br />I think it has the fixed jets.<br />Thank you for taking an interest

 

[rodbolt]

Re: 1986 50 horse rebuilding troubles

ok<br /> take the air box cover off and remove the air box, you will see a small jet at the top center of the carb. with the engine running use a toothpick and block off the jet. if it runs better either the idle pick up tube in the carb is clogged or you have an airleak. sometimes I have to rejet them due to age and throttle shaft wear. I have a 98 115 that had a lean sneeze problem since new. I got it due to a blown piston and a trashed shift clutch and fwd gear. it would never idle so they just kept the idle at 1000 and slam shifted it. I rebuilt the power head and the lower and added OMS. sure enough it snezzed and sneezed. I went from 42 idle air jets to 32 to richen the mix. still had sneezing problems. finnaly took a drill and opened the idle pick up passages from .03" to .04" and opened the air jets back to .038" idles perfect at 650 RPM in gear. took it out yesterday and idle the entire distance acrossed kitty hawk bay. so sometimes rejetting is nessasary. when you use the tapered end of a tooth pick you can actually alter the airflow the idle mix gets. the idle pick up tube is the skinny necked down one inside the emulsion tube that sticks in the fuel bowl well. the idle air jet limits the amount of air mixed with fuel the tube transfers to the aft end of the throttle plates . so by playing with the air jet with a tooth pick you can get a feel for what is happening. also have you tested the spark and the compression yet? and did you rebuild the carbs while the rest was apart ?

 

[rolmops]

Re: 1986 50 horse rebuilding troubles

Hello Rodbolt.<br />The compression is 130 psi on both and the spark is good.The tooth pick trick did not show any difference.The carbs were gone over before I got it and I went over them again a few days ago<br />I will put it in the water later this afternoon and see what it does.

 

[rodbolt]

Re: 1986 50 horse rebuilding troubles

another trick is use a propane tourch. dont flame it just use the gas to richen the mix to find airleaks and such. be aware propane settles in the cowl and is very flammible. use only with good ventilation but it will find air leaks. fogging oil can find them as well

 

[umblecumbuz]

Re: 1986 50 horse rebuilding troubles

You're supposed to use a NEW toothpick, Rolmops!<br /><br />That's a neat trick - i must try and remember it.

 

[rolmops]

Re: 1986 50 horse rebuilding troubles

Well,I got her on the water.Had it idle for like 10 minutes and after about 3 minutes she started to sound really sweet.I took it out of the marina and very carefully following the break in rules had it out on the water for about an hour.<br />After turning the engine off,it dumps fuel,I think out of the carburators so I will check the floats and shut off valves.It also had a real hard time starting after having it run for half an hour.These problems however, are miniscule.The point is that for the first time in my life,I built a machine that came to me in pieces in a box,and now it runs and does what it is supposed to do! I would like to say a big thank you to all the good people that visit this website and share their know how.You have greatly enriched my life and given me a very good feeling of accomplishment and satisfaction.