Machanics are stumped

[pulpwood]

Re: Machanics are stumped

Thanks for the info was wondering how you sealed off ports when piston doesn't fully close them off. I still haven't been able to go run since I got carbs back on, might have time next week.

 

[backyard mechanic]

Re: Machanics are stumped

i would use fuel.... for spraying. water id keep away from electronics...


would crankshaft seals or bad reeds make a lean condition?

are you mixing 50:1 tcw-3 gas oil mix is it pre-mixed?

Exactly!!! Air leaks are the answer! While compression is important for compressing fuel before spark, the action of the piston also "works" (opens and closes) the reed plates. Any air leak from bad gaskets, broken or poorly seated reeds, or bad upper or lower crank seals may decrease that vacuum in the crankcase and therefore it's a good bet why you have a bad idle condition.

How to check that:
At full throttle take a business card and hold it about 1/2 - 3/4" in front of the carbs. The card should vibrate/oscillate. If it saturates with fuel, your reeds are bad.

If the idle clears up with motor oil sprayed around carb and reed plate gaskets you have an air leak.

If you pop off the flywheel and it's saturated with oil underneath, your crankshaft seal is bad.

All this is of course what you should be looking for as well as ASSURING your carbs have been cleaned, floats set, timing synchronized, etc. There is also the possibility your ignition system or coils are going south so check for voltage/ohm readings on those as well.

 

[pulpwood]

Re: Machanics are stumped

Exactly!!! Air leaks are the answer! While compression is important for compressing fuel before spark, the action of the piston also "works" (opens and closes) the reed plates. Any air leak from bad gaskets, broken or poorly seated reeds, or bad upper or lower crank seals may decrease that vacuum in the crankcase and therefore it's a good bet why you have a bad idle condition.

How to check that:
At full throttle take a business card and hold it about 1/2 - 3/4" in front of the carbs. The card should vibrate/oscillate. If it saturates with fuel, your reeds are bad.

If the idle clears up with motor oil sprayed around carb and reed plate gaskets you have an air leak.

If you pop off the flywheel and it's saturated with oil underneath, your crankshaft seal is bad.

All this is of course what you should be looking for as well as ASSURING your carbs have been cleaned, floats set, timing synchronized, etc. There is also the possibility your ignition system or coils are going south so check for voltage/ohm readings on those as well.

I don't have a bad idle I mix feul 50:1 in new gas tank with new fuel hoses all the way to carb. I have clean carbs seven times including pulling all plugs and replacing unless just a bad carb they are clean. I have good timing at ide and at wot carbs open and shut at same time. this is what is thowing off every one the one machanic I took to, replaced head gasket and cleaned carbs why he changed head gasket don't know didn't change anything not going to waste money on him guessing I can guess and not waste money no one else close to me, I hope to get another set of carbs next week to try on boat see if that works, but will try card method to see if any gas coming back out of carbs thanks have checked under fly wheel it's dry not for sure about bottom seal. Thanks for all info

 

[Faztbullet]

Re: Machanics are stumped

Did you install new kits in carbs and what brand? I have had too many problems with the Sierra kits so I only use OEM now. What I have found is the bowl gaskets are to thin to seal around emulsion/pull over tube in center of bowl..this is a internal air leak in carb. If they are OEM kits try opening the roller gap as some older engines like a little more timing before fuel is delivered. Also if your carbs has the fixed jet AND adjustable needle in FRONT turning needle CW is lean and CCW is rich,if it has the adjustable needle on REAR CW is rich and CCW in lean as this is a air circuit not a fuel circuit....

 

[jonesg]

Re: Machanics are stumped

I have seen some 3 cylinders over the years that just dont like the factory suggested set-up and like a little more timing before fuel, try opening the roller to a 1/8 gap and retest.

Yeh, a bit more advance is what I thought might help, sounds like its bogging.

 

[pulpwood]

Re: Machanics are stumped

I'm going to try moving the roller out some but will be next week. carb kits are oem. Let you know how it goes heading out of town this weekend. Thanks for all the help

 

[backyard mechanic]

Re: Machanics are stumped

Pulpwood... read the post again. If your carbs are clean, gas is good and all else you say is tip top shape you would not have an issue. There is more to it that that. Mechanics are stumped because they are not listening or willing to hear what others are saying. So if all else is good.........................
Check reeds and check the ignition. Something is at fault here.

 

[pulpwood]

Re: Machanics are stumped

Pulpwood... read the post again. If your carbs are clean, gas is good and all else you say is tip top shape you would not have an issue. There is more to it that that. Mechanics are stumped because they are not listening or willing to hear what others are saying. So if all else is good.........................
Check reeds and check the ignition. Something is at fault here.

I realize what you are saying I can promise you I have checked timing with a timing light at all different stages, I have checked spark on all three cylinders with spark tester jumps over a 5/8 gap. I have looked at every reed best I can when pulling off carbs everything looks tight and clean, have also tried decarb on engine and I'm not saying that it is not any of these things you or anybody else is suggesting, because it could be a bad carb period or a bad reed that you can not see without tearing down, or a bad crank seal.I have checked and retested so many things so many times its getting redundant. Have let three machanics work on it and still same issue. If I find out whats wrong it will problably be something simple and promise to let you know.

 

[ezeke]

Re: Machanics are stumped

........Timing is set at 5 deg at idle and 20 deg full throttle.......

Why 5? at idle? What does the linkage and syncronization instruction in your factory manual specify?

I believe that the manual will specify TDC +/- 1?, or just say TDC at idle.

BTW, is the number on your welch plug on your engine block the same as on your number plate?

 

[pulpwood]

Re: Machanics are stumped

I have tried bringing it down to tdc but it will shut down. 5 deg is what other outboard are generally set and it would idle smooth when set there. I went today to the river and tried several different things I even advanced the timing to 8 deg then to 12 deg but as soon as I put it in gear and give throttle it would shut off. Even put new ngk spark plugs in today no difference reset linc and sinc no change what ever I do same problem. I have some more carbs to try coming tomorrow.

 

[SparkieBoat]

Re: Machanics are stumped

I think Back Yard is on to something with the business card in front of carbs. I have a 70 rude doing the same thing..cranks and idles ok...then under power bogs out..I checked carbs for even spray and the top one was spraying gas out in my face..I am currently replacing the reeds and will let you know the result..I strongly encourage you to do the business card test....I suspect a bad or stuck reed.

 

[4strokes]

Re: Machanics are stumped

Make sure the timing advance plate under the stator is not sticking or hanging up when the engine tries to rev past idle.

Just my 2 cents worth because I've had that same issue on more than one over the years, this is normally caused by excessive heat melting the wire harness cover making it hard or in some cases sticky.

 

[nymack66]

Re: Machanics are stumped

Wrong carburetors on this engine, The part numbers for the Year,Make,Model you posted does not match.
Go to http://shop2.evinrude.com
If you can post pictures it will greatly help, this forum lacks the pressure for pictures, I however seen numerous times over where folks were able to nail it right on or simply by posting pictures.
Use www.photobucket.com its fast easy and free to post pictures and link them here.
Here is the parts number for your make and model..

http://s527.photobucket.com/albums/...ot move/?action=view&current=Screenshot-2.jpg

 

[Tim Frank]

Re: Machanics are stumped

Even put new ngk spark plugs in today no difference reset linc and sinc no change what ever I do same problem. I have some more carbs to try coming tomorrow.

Are you running NGK?
Have you tried Champions?

 

[ezeke]

Re: Machanics are stumped

I have tried bringing it down to tdc but it will shut down. 5 deg is what other outboard are generally set and it would idle smooth when set there. I went today to the river and tried several different things I even advanced the timing to 8 deg then to 12 deg but as soon as I put it in gear and give throttle it would shut off. Even put new ngk spark plugs in today no difference reset linc and sinc no change what ever I do same problem. I have some more carbs to try coming tomorrow.

Yours is not "other outboards". The manuals are quite specific as to timing and 1984 and 1985 70HP motors idle at TDC +/-1.

 

[pulpwood]

Re: Machanics are stumped

The spark plugs I had before were new champions told to change to ngk gave them a try no different Yes carbs are for 1984 70 mine is a 1985 70 motor told should not make a difference, work with last owner. As for timing machanic said he generally has to set timing on those motors to around 8 deg. All I know is will not run at tdc. Working on it again this afternoon when I get off work, got a guy who races boats to help tell you what we find. Sorry no pics were posted first time using forum wasn't for sure how to post them. Again thanks for all the info

 

[jay_merrill]

Re: Machanics are stumped

Although I doubt they are the source of the problem you are experiencing, I would lose the NGK plugs - OMC motors tend not to like them. Further, a lot of experienced OMC mechs advise that you use Champion "J plugs," instead of the surface gap type.



???

 

[nymack66]

Re: Machanics are stumped

The spark plugs I had before were new champions told to change to ngk gave them a try no different Yes carbs are for 1984 70 mine is a 1985 70 motor told should not make a difference, work with last owner. As for timing machanic said he generally has to set timing on those motors to around 8 deg. All I know is will not run at tdc. Working on it again this afternoon when I get off work, got a guy who races boats to help tell you what we find. Sorry no pics were posted first time using forum wasn't for sure how to post them. Again thanks for all the info

I can tell you this much, do your self a favour, find the correct carbs and save yourself a lot of grief and time, I will also add my engine was 140 with 225 carbs ran like crap, never work correctly, I was told this is not an issue by my so call tree shade crook, well I spent the money and bought the correct carbs jet each side to the manual instructions.

 

[SparkieBoat]

Re: Machanics are stumped

you mean that the carbs on a 84 70 HP and a 85 70 HP motor are different?? big difference between that and putting 225 carbs on a 140...big huge gigantic difference...I still say it is one of his reeds.

 

[Iratherbefishing]

Re: Machanics are stumped

I really think you need to try new reeds. This is a inexpensive part and if reeds are not closing are opening right it will cause motor to bog.

??? Did this motor run hot?