1 Doggy 71 Evinrude 50173S with a tick.

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Kitakojo

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Aug 3, 2011
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I have a real head scratcher on my end:confused:.

Hello everyone & thanks for reading this thread. I'm a new member to the Iboat forum. I have been searching the Internet for answers and now I have to ask for your help.

I recently received a 71 Evinrude 50HP outboard engine on a 76 Glastron T156 Sporster boat. The boat is in really nice shape for its age but the motor has issues. The previous owner stated that he was pulling a skier when the engine wouldn't pull a 120 lb. skier. He stated the motor was doggy at full throttle. This happened about 8 years ago according to him. Makes me wonder if he knows what is wrong with it but doesn't want to say.....

I pulled the carbs & cleaned them, "they were very clean"! I replaced all the fuel lines/connectors, replaced spark plugs, checked the motor over for loose wires and connectors, did a compression test and found 170 lbs. on both cylinders, checked the spark at crank and it was good, changed the oil in the lower unit and set the carbs idle mixture screws at 5/8 out from seat. I ran the motor with the muffs seem to have a miss and doggy at full throttle but I knew I needed to be in the water for a true carb setting a test ride.

This morning I head to the lake with the family whom my 4 kids were excited for their 1st boat ride. Told them it's a trial run not a vacation. Put the boat in the water it fired right up and we proceeded on our way at about 1/4 to 1/2 throttle. The motor seemed to hesitate at idle and sounds like it has a miss all the time. I proceeded to go full throttle after warm up and the boat than sounded like a 4 barrel carb being opened up but with no response. Basically it fell on its face. I stopped and dropped anchor. I proceeded with checking the plugs which the bottom plug was wetter than the top plug. I tried setting the mixture screw lean and rich. it seemed to rev up better with the top carb richer than the bottom carb, which made me think I was sucking air some where, so I did the carb cleaner spray check and found no leaks on the seals or carbs. After several attempts of adjusting the idle mixture screws, I loaded it back on the trailer and headed for home. Like I said earlier the motor has a miss and it seems to be all the time it never smoothened out, almost like a tick. It sits and twitches. Is it possible to have good spark at crank and lose it when it is running? or is it possible the timing is off? How is the timing set?

Any ideas would be greatly appreciated. Maybe someone has had the same issue just on a different size motor.

I may put it back on the muffs and idle it for a while to see if one spark plug is warmer than the other. I know at the lake when I took them out they weren't to hot to touch after 10 minutes of running.

Please help, my 4 kids our looking forward to some fun before school starts up in September.

Thanks,

Kitakojo
 
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BonairII

BonairII

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2,727
Re: 1 Doggy 71 Evinrude 50173S with a tick.

Search for link and sync here to make sure timing is correct. Make sure all passages in carb are clean, also check float level. It's possible you have a coil/ignition prob when engine is warm/hot.

You sure about that compression? 170 seems very high.
 
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Kitakojo

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Re: 1 Doggy 71 Evinrude 50173S with a tick.

I rechecked the compression today and came up with 145 lbs. on each cylinder. Checked the spark and I have a really nice blue arc which throws an arc 1/2" to 3/4". Is it possible to have a plugged exhaust? It acts like an old push lawn boy mower I had. once in while you would have to pull the muffler of and clean it out do to lack of power. Does this Evinrude motor E50173S port the exhaust out the propeller housing? Not sure how to check the timing, still searching the net for information or a orginal omc service manual.
 
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Daviet

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Re: 1 Doggy 71 Evinrude 50173S with a tick.

What is the idle set at, should be 700-750 RPM, in gear in the water.
Look in the "Top Secret File", there is a topic there by Joe Reeves on how to set the timing, as well as other topics you might want to read.
 
oldrudedude

oldrudedude

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Re: 1 Doggy 71 Evinrude 50173S with a tick.

From what you said, the PO said it was running well...... then suddenly would not pull a 120lb skiier. Sounds to me like something suddenly broke/plugged/failed/went out of adjustment.

Three basics are compression, spark and fuel.

Compression sounds good.

Spark should jump 1/2 in gap. Timing at idle should be 3* btdc. Timing at WOT (wide open throttle) should be set to 19* btdc at 3500rpm.

** WARNING ** do not state on this forum that you have revved your engine over 2000rpm while on muffs because you run the risk of blowing your motor and/or turning up the noses of many forum members.

Idle timing ( 3* btdc) is set with the stop screw located just above the pivot of the engine throttle arm. WOT timing (19* btdc) is set with the stop screw "(stops the advancement of the throttle arm) located just under the flywheel. See "Top Secret Files" timing method.

However, if there is a noticable difference between the condition of the plugs on each cylinder...... something other than timing is the problem. Carb or bad plug/coil. First take your boat out on the water and check for consistancey of spark on both cylinders with a timing light. If the timing light shows a nice consistancet of spark when the engine appears to be missing, suspect fuel supply.
 
oldrudedude

oldrudedude

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Re: 1 Doggy 71 Evinrude 50173S with a tick.

Original factory service manual here http://www.marineengine.com/parts/johnson-evinrude-manuals.php?Year=1971&HP=50&Model=50173

Exhaust does exit through the prop, but there is are two rectangular exhaust relief ports at the rear of the leg just below the powerhead. They are there to make starting easier when the foot is submerged. During operation there should be a little water spitting out of there with the exhaust. This is one of the methods of determining that the water pump is pumping water.
 
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Kitakojo

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Re: 1 Doggy 71 Evinrude 50173S with a tick.

Well I'll update my followers on my progress. I installed a new fuel pump gasket kit today, removed flywheel and inspected the stator, key way and fly wheel magnets. Took it out of the shop and filled a large water trough for a test tank. Fired it up and still had my miss at idle and at half throttle. I hooked up a timing light and watched the light at idle and than at higher rpms seemed to hestitate the strobe quit often at higher rpms it did this on both cylinders. I did not notice the timing light hesitated at idle but at 1/2 throttle it just would quit for a 1/2 of a second right at the time the motor would hesitate. So Im losing spark more noticable at higher rpms.

Talking with two other individual they suggested the power pack is bad. Could it be that the power pack is bad and causing me this headach? Does the power pack act as your timing advance? I dont believe it is the coils since it hesitates on both cylinders. What is the OMC part# for the power pack? I have someone whom has one but needs a part# to make sure it is correct. Its amazing how the electronics mock my 73 Evinrude snowmobiles ignition system.

At idle the timing showed 3 degrees btdc.

Thanks for the help & please keep it coming, I believe I'm 1 day closer to a resolution. :redface:
 
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Kitakojo

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Re: 1 Doggy 71 Evinrude 50173S with a tick.

I might be blind or tired but where is the top secret file on the forum? Please only one answer will do.
 
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Kitakojo

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Re: 1 Doggy 71 Evinrude 50173S with a tick.

Yesterday I decided to do the ignition upgrade from the original 71 to a 74 50hp Evinrude Ignition system. I started with the stator and the timing base assy. Everything went together just fine, I used the old stop or linkage arm on the timer base assy. since the two were different. The stator harness had a ground wire which the original one did not so I connected that to the engine block. I upgraded the power pack and replaced the coils. Put it into the test tank and fired it up. It seemed to start right away with very little effort from the starter. I notice right away that the miss was gone and when I increased the rpms with the timing light connected to each one of the spark plug wires, there was no hesitation or miss in the strob light.

Well you know I had to load the family up & head to the nearest lake for a test run which we did and wow what a difference a motor that would actually accelerate and plane the boat out. We spent about 2 hours cruising around, which the kids loved. So to everyone whom helped thanks a million$$$$$$. Used ignition system replacement cost $150 thanks to a local dealer.
 
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