Topic: 1973 6Hp Evinrude Fisherman hard starting cold – Page 4

This topic has 75 replies, 9 voices, and was last updated 2 years, 11 months ago by fleetwin.

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December 9, 2020 at 6:10 am #224689
billw
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US Member
Well, 98 seems okay, especially considering that Fleetwin’s problematic 6 hp had a reported compression of 75. I know, it might be a gauge difference, but hey, you’ve got more than him! If there is any problem at all, I would be thinking now about crank case pressure and/or crank case recirculation. I’m not sure how the 6’s recirculation works….the diagram almost appears like it has none, per se. I guess it still bugs me that the needle is 2 1/2 turns out and you are getting a blackened lower plug, but not on the top.But at some point, you may have to ship it and move on.

Long live American manufacturing!
December 9, 2020 at 6:19 am #224690
fleetwin
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US Member
billw wrote:

Well, 98 seems okay, especially considering that Fleetwin’s problematic 6 hp had a reported compression of 75. I know, it might be a gauge difference, but hey, you’ve got more than him! If there is any problem at all, I would be thinking now about crank case pressure and/or crank case recirculation. I’m not sure how the 6’s recirculation works….the diagram almost appears like it has none, per se. I guess it still bugs me that the needle is 2 1/2 turns out and you are getting a blackened lower plug, but not on the top.But at some point, you may have to ship it and move on.

Yes, his compression seems much better than mine….My low readings are probably due to my snap on compression gage with the valve up by the gage, also affected by my low cranking speed sitting on my work stand with the recoil facing the wall….
I too suspected crankcase issues with my engine, especially since I had just rebuilt the powerhead, “assssumed” I had scrwed something up. I went through all the trouble of swapping my rebullt powerhead for a used one I bought on ebay…. My engine ran identically on both powerheads….Didn’t start real well, not a great idle (for a 6hp anyway), idle needle set out too far, stumbled on mid range acceleration, and lack of WOT power. I too pulled plug wires to check cylinder balance and found both cylinders seemed to be contributing equally.
We have suspected carb issues on my engine, but I am confined to quarters so haven’t had the chance to try another carb. Perhaps we both have similar carb issues….I looked for obvious errors in mag plate installation/advance on my engine, but found nothing obvious. .
December 9, 2020 at 8:20 am #224692
crosbyman
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Canada Member
billw…“. I would be thinking now about crank case pressure and/or crank case recirculation. I’m not sure how the 6’s recirculation works ?

what about the side recirculation hose from lower crankcase to upper bearing…. would that be a source of problem if clogged….. stopping accumulated oil/gas from being recycle upwards ????

Joining AOMCI has priviledges 🙂
- This reply was modified 4 years, 4 months ago by crosbyman.
December 9, 2020 at 9:47 am #224743
fleetwin
Participant
US Member
Well, that recirc system could be a problem, but it would probably only affect the idle quality….That being said, you may want to pull the powerhead off to check the lower seal components that are often ignored/left out/improperly installed during servicing.
December 9, 2020 at 4:18 pm #224751
fleetwin
Participant
US Member
Thinking about your mag plate/module pictures (daydreaming) while being dragged around BJs today….. With those extra leads coming out of the mag plate, are you sure the mag plate is advancing all the way?? Is the carb butterfly opening fully? The extra wiring could be limiting mag plate movement/timing…
Are you sure the throttle gears are indexed properly? If not, the mag plate may not be advancing all the way. Another thought, those throttle grip throttle sleeves are often inaccurate also. So, judging start up throttle position by the twist grip/throttle position sleeve indicator may be misleading us here about throttle position during start up….
Perhaps all this was discussed earlier in the thread, just being lazy not reviewing the entire post…
December 10, 2020 at 2:50 am #224792
JOHN HOLBIK
Participant
I feel your pain.I have fixed thousands of older OMC engines but have been stumped by the 3hps.I bought a used 61 JW many years ago very low hour motor.I put a lot of hours on it on my trapline and fishing on weedy rivers.One day the motors starts right up but only has about 85 percent top speed it sounds like it is running rich or plugged exhaust when it is about to run out of gas it speeds up normal.I have spent at least a hundred hours over the years trying new things even drilled in more exhaust holes in the leg.I have two other 3hp that do the same and one fourhp.My buddies low hour 67 3hp is the same.
Here are two similar problems I have had over the years Brand new 1987 9.9 Evinrude we portaged the motor and went to the trapping cabin went out fishing went to go back to the cabin motor dies flooded pull off hose crank starts up but dies as soon as hose is replaced row back to cabin return home with TN28 left at cabin for emergencey.Get home tear carb a part clean reassemble happen to look down carb throat see an obstruction remove with needle nose.It was a tag from the motor said it was inspected by number 159.
I had a 4hp i used to go back and forth to work had to cross 1/4 mile stretch of lake.The motor started fine but you had to adjust the high speed every time you used it on rainy humid days it ran real rich.I took the carb off every thing inside clean and to spec I got to thinking about the inspection tag on the 9.9 i held the carb up to good light and saw nothing then I could barelysee something in the top of the throat pulled with needle nose it was a dried up tree leaf motor ran great after.
I love the 3s but I just hate to admit defeat.
John
December 11, 2020 at 7:58 pm #224986
Tom Bertulli
Participant
Wow, What brain trust here. There is almost too much to answer at one time but I’ll try to address each of you.

To John Holbik. I Know how you feel but i’m sure most of us here have as much fun trying to fix this old stuff as we do running them. It brings me back the 50’s & 60’s when my dad could fix anything with just a library book. Spent a lot of time in the basement with him. What he couldn’t afford, he made. He wound his own A/C welder in the late 30’s. The guys in the electrical shop near us gave him scrapped transformers for the iron core and scrounged magnet wire for him. We had that welder in the garage until he bought the “Miller” in 1970.

Cosbyman & Billw I cleaned the rubber line and ports on the side of the block with carb cleaner, wire and compressed air. I did not see any dirt but the motor now starts in 2 pulls cold at just over 1/2 throttle. I’m reading throttle position from the cam under the mag plate, because Fleetwin is right- those handle markings are always suspect. I’ve Cut back the LS needle to just over 2 turns, the motor idles down just a bit slower and is still smooth.

Fleetwin, There is no linkage binding the mag plate- full range of motion is smooth and without major slack. Starting position is read on the throttle cam. Good point about the flywheel / key geometry. A small change at the flywheel centre produces a large change at the flywheel edge – can’t believe I missed such a simple concept. Part of the issue with this motor was the excessive slack in the mag plate bearing (which I shimmed out using a piece of .005 brass shim stock). No matter how well I set the points, they would always end up way off after 10 minutes of running. Have you checked for slack in yours which would throw the point setting off during use? I can’t think of anything more to advise you on. I have more thinking to do on this concept of OMC timing. Please school me here anyone.

1 When measured against the index marks on the mag plate ( and assuming points properly set) A timing light will show the spark firing in the same spot REGARDLESS OF THE THROTTLE HANDLE POSITION. yes or no?

2 Spark timing at the plug is governed by the movement of the mag plate because it’s movement changes the relationship between the when the points close and when the piston reaches top
dead centre. Yes or no? Or is my thinking completely screwed?

3 As engine speed increases, is the spark timing is advanced or retarded? For example as the mag plate moves to the right and engine speed increases, is the timing advancing or retarding? Should be advancing – correct?

Thanks all
December 11, 2020 at 8:06 pm #224987
Tom Bertulli
Participant
I’m just trying to figure this website out. I have been answering to everyone in one mail and this may not get to everyone unless I reply individually. If i reply individually, it alerts you directly by email, then you can choose to got o the site – am I correct?
December 12, 2020 at 5:57 am #225016
billw
Participant
US Member
I would say the answer to your questions are all., “Yes.” With regard to question one, there will be some very minor fluctuations, but the general statement is true. You should be able to prove that with a timing light.

Question three, yes, as the mag plate moves towards full throttle, the timing advances, usually a good deal beyond top dead center. At lower speeds, it will be retarded, sometimes to the point where it actually fires AFTER top dead center. The actual maximum and minimum degrees of advance and retard depend entirely on the specific motor’s design.

Whether being fired by points or modules, I think you will find that if all other things are okay with the engine, then if you get a timing light flash anywhere between the two index marks, it will be a good runner. We all strive to make it exact; but the engine will be amazingly tolerant as long as it fires between the two marks…or even on either mark. Now what you can do, is run the engine fast, run the engine medium and run the engine slow and see if the flashes come outside the marks at any time. With points and a worn mag plate, you would likely see the flashes move in and out of the marks, as you move from fast to slow and back to fast. The modules should improve this; but if the plate is worn enough, you might still see fluctuation outside the marks. It’s worth the experiment.

Long live American manufacturing!
- This reply was modified 4 years, 4 months ago by billw.
December 12, 2020 at 9:15 am #225020
fleetwin
Participant
US Member
Like Bill says, yes to all three questions. The timing light should show the same position between the marks regardless of RPM and throttle setting, but there will be a little variation, especially with a worn mag plate. The problem here is that we have no timing grid, or advance specs. Perhaps I will make some markings on a normal 6hp, then compare them to mine. Seems like you are slowly getting this thing dialed in…Two pulls cold start is great, and you realize that the twist grip throttle indications are usually off a bit. Does it still hesitate when you accelerate? Pull the prop off, and read the OMC part number/diameter/pitch….It is possible that someone installed a 8-9″ pitch prop on this engine, which is for the older 10hps…The 6hp would never be able to spin this prop…It will bog and seem to have not top end power…Kinda like trying to accelerate in a VW bug in fourth gear at 20MPH…
And years ago, I probably just would have tossed my 6hp problem child in the back of the shop somewhere and forgot about it……… But, in my advanced age, I have become more stubborn, and will keep at it until I figure it out, or someone else has a look and quickly points out something basic I have overlooked. But, it is good to put it aside for awhile, oftentimes the solutions will come to me late at night in my dreams…
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