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  1. #1

    Default Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    Good Evening, my Name is Joerg and I'm new member here. Upfront many thanks for alle the contributions which I've been able to read prior to membership, this already helped a lot building up knowledge about my motor, hence made some improvements! THANKS!

    I run Fletcher GTO with Evinrude 70HP from 1984, bought it in UK a year ago, step by step made improvements in RPM in the meantime. in the beginning, the motor completely bogged and I could not manage to rev beyond 1500 RPM though compression was ok at purchase (+/- 125PSI). I deployed Champions spark plugs, adjusted ignition with Strobolight, cleaned carbs twice including Kit parts, did fuel pump, gaskets, etc. I'm now stuck at 4.800RPM with some limited acceleration. Once I press the starter Solenoid for fuel priming during water operation, it seems to ignite some heavy afterburner and jumps to 5.600RPM immediately. But this is where it should go without pressing any ignition key opening the Solenoid, shouldn't it ? So my guess of course is CARBS. I have to admit that I obviously did not clean all parts of the Carbs since I have left plenty of welch plugs .

    CARBS mounted are:
    top -> label 394810 70 MX 21 B J (add'l: 328568) / main jet 52D / other jets 43or45 & 68
    mid -> label 394811 70 MX 13 B J (add'l: 328568) / main jet 52D / other jets 47or42 & 68
    bot -> label 396964 MX 15 C K (add'l 330943) / main jet 57!D / other jet 28 & nil return due to construction

    my question now: should I also remove the welch plugs ? which of them ? (Pic1 & Pic2)
    summer was way too short (Pic3)

    looking forward to get some insights ! handwidth of water ...
    .. under your keel
    Joerg


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    Last edited by Cape Horn; 09-08-2019 at 04:02 PM.

  2. #2
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    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    Pressing the ignition key inwards causes the fuel flow to completely bypass the carburetors to flow directly into the intake manifold. My guess is that you haven't manually cleaned the high speed jets that are located horizontally in the bottom center portion of the float chambers., way in back of that drain screw.... and if so, clean them carefully and thoroughly with a blunt edged (NOT Pointed) piece of single strand steel wire.

    Solvent nor pressurized air just doesn't do that job properly.
    We occasionally have questions. If you fail to answer, it may affect ours.

  3. #3
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    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    looking at part breakdowns the bottom carb maybe from a 1985 70 middle carb. the 394810 and 394811 are correct, you should have another 394810 on the bottom, does the 396964 carb have parts 22,19, 17?

  4. #4
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    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    The tubes within the nozzles do not appear to be the same on all 3 carburetors.---Any more close up pictures of them..

  5. #5

    Thumbs up Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    Quote Originally Posted by joereeves View Post
    Pressing the ignition key inwards causes the fuel flow to completely bypass the carburetors to flow directly into the intake manifold. My guess is that you haven't manually cleaned the high speed jets that are located horizontally in the bottom center portion of the float chambers., way in back of that drain screw.... and if so, clean them carefully and thoroughly with a blunt edged (NOT Pointed) piece of single strand steel wire.

    Solvent nor pressurized air just doesn't do that job properly.

    thank you Joe for your fast response ! I did clean both drain screw and unhinged high speed jets located in the bottom of the bowls twice. the jet holes look healthy, I see clear light at the end of the tunnels. also thoraxial blowing / puffing through the jets works great. what I did not do with the whole battery of Carbs is ultrasonic bathing. Cleaning has been done with steel wool, WD40, wires of different caliber, brake cleaner, pressurized air. I documented the differences in carbs construction further down. best regards Joerg
    Last edited by Cape Horn; 09-09-2019 at 04:14 AM.

  6. #6

    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    Quote Originally Posted by scalhoun506 View Post
    looking at part breakdowns the bottom carb maybe from a 1985 70 middle carb. the 394810 and 394811 are correct, you should have another 394810 on the bottom, does the 396964 carb have parts 22,19, 17?


    thank you Scalhoun506 for your fast response ! top & middle Carb do have 22/19/17, bottom carb does not ! Also 25/26 is missing at the bottom carb. furthermore all 3 carbs do not have 30/31 since they refer to 75HP model which is ok. pls also refer to my reply to racerone further down requesting more pictures.

  7. #7

    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    Quote Originally Posted by racerone View Post
    The tubes within the nozzles do not appear to be the same on all 3 carburetors.---Any more close up pictures of them..

    thank you racerone for your fast response ! yeah, idle tube of the lower carb has 2 differences in my eyes-> no tiny hole behind the trottle valve, also some tapered and tighter intake hole at the bottom south (top&mid carb holes at this south end of little idle tube are slighty broader but do not stick out surrounding tube, bottom carb hole of little idle tube is tapered / tighter but sticks out surrounding tube). there are more
    construction differences in the bottom carb which I tried to illustrate in those pictures. I'm limited to 6 Pics per post so I'm going to put more answers on your post best regards Joerg
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    Last edited by Cape Horn; 09-09-2019 at 05:11 AM.

  8. #8

    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    more Pics
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  9. #9

    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    more Pics ..
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  10. #10

    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    more Pics ..
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  11. #11

    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    finally still some more Pics ..

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  12. #12

    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    [QUOTE=scalhoun506;661759]looking at part breakdowns the bottom carb maybe from a 1985 70 middle carb. the 394810 and 394811 are correct, you should have another 394810 on the bottom, does the 396964 carb have parts 22,19, 17?

    Scalhoun506, I wouldn't be too sure about those number plates stating model numbers (see Pic below). They are losely fixated by screw only and may have been messed around during 35years. What I found is that there are add'l numbers imprinted in the cast iron on the bottom of the main carb block, see Pictures above, add'l numbers see my Post#1. best regards Joerg

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  13. #13
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    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    again from parts list 26 is for a 75hp, you can get list on this site, and go from year to year easily, definitely different, but back to the other problem, maybe it would work if high speed jets were same sizes #26 but look at parts list for both year carbs

  14. #14
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    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    also check if throttle plates are fully open at WOT

  15. #15
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    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    Item 26 is a plug.------Some years the 75 models had an adjustable mixture needle.----Item 26 is not adjustable and found on 70 and 75 HP models.----And NO that is not a Mercury part.-----The M in the diamond was used by OMC on many parts and is the company logo !-----Some one has switched out the one carburetor from a different year motor.
    Last edited by racerone; 09-09-2019 at 07:21 AM.

  16. #16

    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    Quote Originally Posted by scalhoun506 View Post
    also check if throttle plates are fully open at WOT
    thank you scalhoun506. they are exactly horizontal since I've done the Synch & Link. However during WOT and vibrations it's hard to see and the reed valves in the background produce pretty flutter, but when engine is shut of, they are even and horizontal.

  17. #17

    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    Quote Originally Posted by scalhoun506 View Post
    again from parts list 26 is for a 75hp, you can get list on this site, and go from year to year easily, definitely different, but back to the other problem, maybe it would work if high speed jets were same sizes #26 but look at parts list for both year carbs
    26 is a screw and also built in my upper 2 carbs, it looks like "as designed" according to the exploded drawing. the bottom carb does not have 26 though. regards Joerg

  18. #18

    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    Quote Originally Posted by racerone View Post
    Item 26 is a plug.------Some years the 75 models had an adjustable mixture needle.----Item 26 is not adjustable and found on 70 and 75 HP models.----And NO that is not a Mercury part.-----The M in the diamond was used by OMC on many parts and is the company logo !-----Some one has switched out the one carburetor from a different year motor.
    hello racerone, this seems to be right since 26 is not adjustable but a screw. It is found on the top two carbs of my motor but not on the bottom carb, see Pics above. Regarding switching carb from different year: I found some info regarding early / late carb versions in 1984 / 1985 pls. see pictures. but I can't fully match them to my numbers. the 57D jet in the bottom seems to be "as designed", though. best regards Joerg

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    Last edited by Cape Horn; 09-09-2019 at 09:29 AM.

  19. #19

    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    so I looked around a little: upper (394810) and center (394811) carb seem aequivalent to 1984 archive. In early production of 1984 there should be a further 394810 at the bottom, at later production dates there could also have been mounted 396964 (e.g. 1985 model, see table above), which is mine. My motor's serial number is B002143 by the way. I think that could all be fine and there is nothing wrong with the Carbs and also no messing around with the plates. also the cut in this bottom 1984/1985 carb can be seen constantly from 1985 onwards with no 25/26 in it. nothing wrong with the Carbs from model perspective ?!

  20. #20
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    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    The 3 carburetors on a 70 hp are the same !!---Different part numbers are given due to linkages to open them anfd hook them together.----Some years did not use item 26 and the orifice was an air bleed.-----It would be wise on your part to get the 3 carburetors the same and correct for your motor.----There can be a lot of confusion on the subject.

  21. #21
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    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    racerone is one of the Guru's on this site , i'd try what he said if possible!

  22. #22

    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    Quote Originally Posted by racerone View Post
    The 3 carburetors on a 70 hp are the same !!---Different part numbers are given due to linkages to open them anfd hook them together.----Some years did not use item 26 and the orifice was an air bleed.-----It would be wise on your part to get the 3 carburetors the same and correct for your motor.----There can be a lot of confusion on the subject.
    thank you racerone ! so you mean buying a new bottom carb 394810 or 394811 ? That sounds conclusive since it assures having same set of carbs in a row each with same physical construction. what I still do not understand is, why those parts tables (see Pics above 1984/1985) differentiate between lower / upper / middle carbs with individual numbering since they all must be the same ?! any idea ? I'm starting now looking for 39481x ... best regards Joerg

  23. #23

    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    Quote Originally Posted by scalhoun506 View Post
    racerone is one of the Guru's on this site , i'd try what he said if possible!
    thank you scalhoun506 for the recommendation. this helps for orientation since I'm Newbie

  24. #24
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    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    Part # change due to location of linkages.----Location of fuel inlet fittings.------The way those 3 carburetors work and supply fuel to the engine is the SAME FOR each carburetor !!

  25. #25

    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    Quote Originally Posted by racerone View Post
    Part # change due to location of linkages.----Location of fuel inlet fittings.------The way those 3 carburetors work and supply fuel to the engine is the SAME FOR each carburetor !!
    thank you racerone ! ok, great. I now will try to get some replacement lowerCarb 39481x. from what I've seen by now there is nothing available on common trading platforms in Europe, so it may take some time to get one fitting. Glad to have end of season which releases some pressure to get it urgently done. In the meantime I'll now try to do some workaround in changing Carbs so put topCarb bottom and bottomCarb top, maybe that'll help. also I'm considering to treat each Carb individually with some add'l sprayfuel during water operation at maxRPM to locate the sinner. Culprit could then either be the one different from the other two sucking too less despite 57Djet, or the pair of the other two sucking too less with 52D jets due to the dominant 57D suspect. am happy about your courtesy, would be happy about any ideas. that procedure may take some while, stay tuned & best regards Joerg

  26. #26

    Default Re: Evinrude OMC 70 HP 3Cyl 2S 1984 E70TLCRD Bogging / Carburetor Questions

    racerone, scalhoun506, joereeves good Morning ! after doin' those changes, we were out yesterday: Vroooommm, 45mpH @ 5.500 Revs constantly ! I did follow your recommendations in getting rid of NGK B9HS spark plugs which were mounted since purchase, changed to Champion QL77JC4, I did check spark distance with this little tool. Furthermore I did change bottom Carb3 with top Carb1 and vice versa after cleaning and voilą, boooom, it worked. racerone: of course you are right with "all Carbs SAME", but it worked out this way too, so this might save me from buying a replacement Carb 39481x. But I keep your advice in mind anyway. my final guess is that is because of improved ignition though. the NGK plugs always showed dirt and oil on them, the Champion plugs yesterday were pure, clean and dry. There is still some tiny little bogging left from 1000 to 1500 Revs left but I think that could be related to Link / Synch or Ignition timing, I'll manage .. After some other care with liquids compression is now 130+ on all Cylinders coming from 120 a year ago, magic. all in all I'm so grateful that I got your leading edge support ! thank you & best regards Joerg

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